Geo-Frontiers 2011: Advances in Geotechnical Engineering

Pile foundations resulting from dynamic excitation is a complex phenomenon involving complex pile-soil interaction. Pile foundations behave in a nonlinear fashion at large displacements because of the soil nonlinearity at high strain and pile separation. This paper attempts to study the dynamic soil-pile interaction on the nonlinear response under coupled vibration by both experimental and numerical study. This paper presents the small-scale field test results of single piles and 2 x 2 group piles subjected to different excitation intensities. Resonant frequencies and amplitudes are determined for both horizontal and rocking motion from the observed response curves. Artificial neural network (ANN) models are developed based on field test results for the prediction of dynamic behaviour of piles under coupled motion. Importance of different strategies in developing robust ANN models are explored and discussed. Different ANN models are developed using evolutionary learning algorithm and Bayesian regularization algorithm. Various statistical performance criteria and its importance to compare the developed ANN models are discussed. Different sensitivity analyses are made to identify the important input parameters for amplitude and resonance determination.

Pile setup or freeze is the phenomenon of the increase of pile capacity over time during and after the dissipation of pore pressure and the stabilization of lateral earth pressure. Driven piles regain capacity after installation because of the excessive pore pressure dissipation and soil aging, which causes increase in the drained friction angle on pile shaft. This study is designed to determine the mechanism of the soil aging effect on pile setup and to provide engineers a simple, rational, and accurate model for predicting the capacity of piles over time by reviewing, analyzing and investigating collected full-size pile load testing data. Soil aging effect on pile setup, specifically on the growth of the drained friction angle on pile wall, is investigated and formulated by accounting for the factors of over-consolidation ratio (OCR) and lateral earth pressure, etc. A mechanistically-determined prediction model for pile setup by considering the effect of pore pressure dissipation and soil aging is established. The deterministic model is verified with measured pile capacities collected from the existing static load and dynamic test data. A final analysis is performed detailing the accuracy of the developed prediction model compared with the existing statistics-based prediction models.

The Bahía-San Vicente Bridge, with a length of 1,990 meters between abutments, is located in the Chone River estuary in the central part of the Ecuadorian coast. The bridge site is characterized as an estuarine environment formed by alluvial deposits with depths between 25 and 85 meters overlying weathered rocks. The design team decided to build the bridge foundations with open-end steel pipe piles, mainly supported by skin friction. To verify the installed capacity of the piles, high-strain dynamic load tests were carried out. This article assesses the results obtained from the load tests conducted, which have shown considerable increases in the capacity of the piles as a function of time, due to thixotropic characteristics of subsurface materials. Additionally, the results are compared with the load capacity estimated during the design phase, which has allowed setting specific parameters for the soils of the region, for use in future designs.

Accuracy in estimating driven pile capacity at a particular site is limited due to an inability to capture the full complexity of the soil deposit, soil properties, pile drivability, dynamic soil/pile interaction, and pile setup. These potential errors are usually compensated by a safety factor. Development of an in situ testing device, which can replicate the construction condition to the greatest extent possible, to predict the pile capacity at the design phase of a project will result in economic benefits. A reusable instrumented test pile (RTP), which is an in situ testing device, is under development at University of California, Davis. RTP will be taken to field, assembled, driven into ground with a conventional Becker hammer rig, load tested, removed, and reused. The RTP consists of an instrumented tip and a series of 610 mm (24-in) long instrumented modules that are placed between conventional Becker hammer pipe (6.625-in diameter). The RTP instrumented modules are capable of measuring axial resistance, radial stress, temperature, acceleration, pore pressure and inclination. The measurements can be obtained during driving, load testing and setup. The multiple instrumentation clusters along the RTP pile length will provide insight into driving dynamics, installation energy required, tip to shaft bearing proportions, load transfer distribution along the pile shaft, end bearing capacity, and pile setup, among others. It is expected that these measures will improve pile performance predictions, ultimately resulting in foundation cost savings. The initial RTP design, development, and proof testing are presented.

This paper describes a Modified Borehole Shear Test (mBST) and a Modified Direct Shear Test (mDST) and their use to improve the prediction of the load-transfer (or t-z) analysis of axially loaded friction piles. The mBST and mDST enable direct measurement of the t-z curves along the soil-pile interfaces for cohesive soils in the field and for cohesionless soils in the laboratory, respectively, thereby improving the prediction of load-displacement response of piles. As part of this study, two full-scale instrumented static vertical load tests were conducted on steel H-piles and the t-z analysis was used to model these piles utilizing the TZPILE software. In these models, t-z curves established from the mBST and mDST as well as those currently used based on Cone Penetration Test (CPT) data were used to predict the pile load-displacement response. By comparing to the measured responses from static load tests (SLTs), the mBST- and mDST-based models produced closely comparable load-displacement responses. In contrast, the CPT-based models over predicted the loads at a given target displacement, underscoring the benefits of the mBST and mDST.

The main goal of this study is to examine the Load and Resistance Factors Design (LRFD) approach for pile design in a wide range of soil types considering the use of a combination of static analysis methods. First, the reliability-based regionally calibrated LRFD resistance factors for the design of bridge pile foundations were developed for clay, sand, and mixed soils in Iowa. The framework used for this calibration included a more efficient in-house static design method developed by the Iowa Department of Transportation. Then, the benefits of conducting the calibration using the combination of static methods giving due consideration to the soil variability along the pile length is presented. Finally, it is shown that: a) using a combination of methods improves the efficiency in mixed soils, and b) utilizing a more refined soil categorization based on the actual soil profile on a site-by-site basis provides significantly more efficient LRFD approach for the piles.

Floating foundations are often practical when foundations must be placed over deposits of compressible soil and when deep foundations are expensive. The aim of the present paper is to study parameters affecting the behavior of floating foundations, including the kind of floating foundations, depth of excavation, and imposed pressure by the superstructure. Herein, 3 buildings ranging from 15 to 25 stories with gross foundation pressures from 195Kpa to 342Kpa with similar area plan, 40m x 50m, are studied for 4 soil types ranging from very soft to strong type. Their foundations are studied by using numerical method of finite element. Moreover five case histories have been studied based on their records and analytical predictions. Results indicate that in case of low bearing capacity and high settlement, the floating foundations can be chosen as a reasonable alternative considering of technical and economical aspects.

Helical piles are structural, deep foundation elements used as a means to transfer the applied axial and horizontal loads, and overturning moments from the superstructure to the soil substructure, within a specified criterion. The design process is complex and incorporates various degrees of uncertainties. Closed form design solutions incorporate safety factors in order to mitigate the risk from excessive pile head displacements under the load transfer process. Load testing of the piles is the most accurate method of determining load versus displacement behavior in order to validate design assumptions and to mitigate risk. Conventional load testing of applying a load at pile head was the only method used for testing helical piles, until recently when the first bi-directional O-Cell® test was carried out on a helical pile. An O-Cell test comprises a separation of the shaft and toe behavior, as well as other results important for assessing the adequacy of the pile. Based on an actual comparison of the O-Cell test to the results of a traditional pile load test, the O-Cell method is proven cost effective, quicker, and a more accurate method of testing helical piles.

Pile reuse has become an increasingly popular option in foundation design, mainly due to its potential cost and environmental benefits and the problem of underground congestion in urban areas. However, key geotechnical concerns remain regarding the behavior of reused piles and the modeling of foundation systems involving old and new piles to support building loads of the new structure. In this paper, a design and analysis tool for pile reuse projects will be introduced. The tool allows coupling of superstructure stiffness with the foundation model, and includes an optimization algorithm to obtain the best configuration of new piles to work alongside reused piles. Under the concept of Pareto Optimality, multi-objective optimization analyses can also reveal the relationship between material usage and the corresponding foundation performance, providing a series of reuse options at various foundation costs. The components of this analysis tool will be discussed and illustrated through a case history in London, where 110 existing piles are reused at a site to support the proposed new development. The case history reveals the difficulties faced by foundation reuse in urban areas and demonstrates the application of the design tool to tackle these challenges.

Mueser Rutledge Consulting Engineers (MRCE) served as the Geotechnical Engineer for the New Yankee Stadium project in the Borough of the Bronx in New York City, NY. MRCE's responsibilities included subsurface investigation of the site, preparation of recommendations for design and construction, consulting services related to foundations and other geotechnical issues, and construction inspection of foundations. Topography, geology and site history are interesting aspects of the project and the resulting subsurface conditions encountered. The soil and rock profile includes manmade fill, compressible organic deposits, and glacial lake sediments, all underlain by two bedrock formations at depths ranging from zero to more than 45 m (150 ft). Foundations for the new stadium consisted of spread footings bearing on rock, driven pipe piles, and drilled piles. Driven piles were concrete filled and bearing in glacial till, decomposed rock, or bedrock. Drilled piles were socketed in bedrock. Pile capacities ranged from 900–1350 kN (100–150 tons), proven by load testing. Driven piles encountered some problems such as damage during driving and sweep. In some cases, in order to penetrate intermediate harder layers above the bearing stratum, the contractor drove some piles to partial depth, filled the embedded portion with concrete, and then drove to final penetration.

Lack of standard helical design, installation and load test verification criteria has previously limited the use helical foundations. In 2007, the International Code Council adopted AC358 Acceptance Criteria for Helical Pile Foundations Systems. The establishment of the AC358 acceptance criteria quickly led to the inclusion of helical piles in the 2009 International Building Code®. Based upon AC358 and 2009 IBC, the development of a draft NYC Helical Pile Building Code has been completed and is currently under final review. This paper presents the recommended AC358 and 2009 IBC guidelines for the design, installation, and verification of the ultimate helical pile capacity. An overview of the various helical pile configurations in use today is presented along with an evaluation of some 75 North American helical pile load tests. A recommended helical load test acceptance criteria based upon total and differential settlement is also presented for small, medium, and large displacement helical screw piles. Load test data from several helical pile projects is also presented.

The axial and lateral monotonic and cyclic behavior of helical pile foundations was investigated and new helical screw systems suitable for seismic loadings were developed. More than one hundred full scale field load tests were conducted on instrumented helical screw piles installed in cohesive soil. The piles included: plain helical screw piles (P-HSP); grouted (G-HSPs); fiber reinforced polymer (FRP-G-HSPs); and reinforced grouted (RG-HSPs). The (RG-HSP) piles axial capacity was more than twice that for P-HSP, with minimal reduction after cyclic loading, and their lateral capacity was more than 3 times the P-HSPs capacity. A 3-D finite element model was established.

This paper provides a quantification of the inputs for an existing qualitative foundation project planning model, namely ARUP's Sustainable Project Appraisal Routine (SPeAR®) diagram. The goal is to provide an improved mechanism for designers to communicate with clients about the potential benefits of foundation reuse from a planning and environmental perspective for an individual project or group of projects based on the relative value of eight factors: (1) Site Location on Previously Developed Land; (2) Archeology and Historical Constraints; (3) Geological Conditions and Constraints; (4) Sustainability and Materials Reuse; (5) Land Value and Cash Flow Projections; (6) Construction Costs; (7) Consistency in Building Location; and (8) Approvals and Development Risk. For each category a six-point scale is provided that can be fully adopted in any community worldwide to evaluate the absolute and relative benefits between sites, even between disparate cities or countries. An example of the implementation of this modified SPeAR model is provided for a city-center location in Dublin, Ireland.

A new analysis is developed to calculate the response of laterally loaded piles in multi-layered elastic media. The governing differential equations for pile deflections in different soil layers are derived using energy principles, and solutions are obtained analytically. The displacement fields in the soil surrounding the pile are taken to be the products of independent functions that vary in the vertical, radial and circumferential directions. The input parameters needed for the analysis are the pile geometry, soil profile and the elastic constants of the soil and pile. The method produces results with accuracy comparable to that of a three-dimensional finite element analysis but requires much less computational time.

An analysis is developed to determine the response of laterally loaded piles with rectangular cross sections. Soil displacement fields compatible with the rectangular shape of the pile cross section are assumed. The differential equations governing the displacements of the pile-soil system are developed using energy principles. Closed-form solutions for lateral pile deflection and displacements within the soil mass can be obtained using the analysis. The input parameters needed for the analysis are the pile geometry and the elastic constants of the soil and pile. The new analysis allows insights into the lateral load response of square, rectangular and circular piles and how they compare.

Piled embankments are widely used for the construction of roads and rails over soft and/or compressible soils. Traditional design methods, such as BS 8006 (1995), assume that the lateral trust is carried by geosynthetic reinforcement placed at the base of the embankment directly over the pile caps. At the extremities of the embankment both horizontal equilibrium and strain compatibility between the different components, the embankment fill, the geosynthetic reinforcement, the pile group and the soft soil, must be achieved (Love and Milligan 2003). This paper examines the horizontal and vertical deformation, axial tension developed in the geosynthetic reinforcement and bending moment/deflection developed in the pile for a range of complex embankment geometries. The piled embankment model (designed to BS 8006: 1995 codes) will enable the examination of the structural performance in terms of horizontal and strain compatibility.

A full-scale lateral load test was conducted on a batter-pile group foundation that supports the M19 eastbound pier of I-10 Twin Span Bridge over Lake Pontchartrain, Louisiana, to assess the validity of current methodology used to design pile foundations. The test was conducted by pulling the M19 eastbound and westbound piers toward each other using high strength steel tendons. A maximum of 1870 kips (8318 kN) static lateral load was applied in increments. The tested pile group consists of 24 driven square precast prestressed concrete (PPC), 110 ft. (33.5 m) long and 3 ft. (0.91 m) wide batter piles; among which 8 piles were instrumented with In-Place Inclinometers (IPIs) and 12 piles were instrumented with strain gauges. The batter piles were spaced 4.3 pile width in the direction of lateral loading. A seventh-order polynomial curve fitting method was applied, for each load increment, to fit the measured rotation profiles from the IPI inclinometers. The fitted rotation curves were then used to deduce the bending moment, shear force, and soil reaction profiles based on specific mathematical derivations. The calculated moments from curve fitting were compared with the moments calculated from strain gauges, and the results showed good agreements. The soils' p-y curves at different depths were also back-calculated from the derived soil reaction profiles. The resulted p-y curves showed no evidence of a group effect.

The offshore wind sector is undergoing rapid expansion across Europe, driven by the demand for renewable energy and uncertainties regarding fossil fuel supplies. The proposed wind farms are creating significant geotechnical challenges, particularly in terms of efficient foundation design. The majority of wind farms constructed to date have been founded in water depths of less than 30 m. However 70% of wind farm developments to be undertaken over the next 10 years will be located in water depths of between 30 and 70 m. In addition, because of developments in turbine technology, larger 5 MW turbines are coming into operation. The combined effect of larger structures and greater water depths leads to significantly increased vertical, lateral and moment loading on turbine foundations. This paper considers some aspects relating to the reliability of design methods for monopile and jacket structure foundations used to support the next generation of wind turbines.

The petroleum industry endeavors to minimize the environmental impact during oil and gas drilling operations. For instance, by reducing the footprint during drilling operations using a reusable modular platform and a small mobile rig, in 2003 and 2004 Anadarko and Maurer Technology Inc. demonstrated a new foundation concept in the Arctic. Their objective was to drill in an ecologically sensitive area without disturbing the ground surface. Use of an elevated platform in environmentally sensitive areas requires the use of piles to support the elevated deck instead of gravel pads used in a conventional drilling system. The aim of this paper is to introduce an environmentally friendly foundation method for onshore drilling systems, and to conduct a parametric study of different foundations to improve the understanding of these types of foundation designs, by introducing uncertainty quantification for various rig weights and soil conditions (e.g., desert environments and wetland applications). This paper introduces a case study on pile capacity calculations depending on various soil types and pile types, and sets the basis for a full reliability analysis on this type of foundation.

The new pneumatic caisson method (NPC) characterized by remote controlled soil excavation and removal has high requirements for construction management and timely information acquisition. To ensure construction accuracy and safety, site monitoring and measuring is indispensable. This paper summarizes the monitored items, field instrumentation layout, and data analysis and feedback methodology for the NPC construction. Combined with a tunnel shaft construction in Shanghai, in which the NPC method was used, typical monitored results were analyzed. Finally, a real time monitoring program, developed based on the industrial control configuration, was introduced. This program supports real-time monitoring, warning and alarming, and data analyses.

As the tallest building in Cincinnati, the 45 story Great American Tower at Queen City Square is not only changing the downtown skyline, but is also contributing to the advancement of the state-of-the-art use of auger cast-in-place (ACIP) piles as settlement reducers. Predicted settlements of a traditional mat foundation were excessive, and the costs and construction time associated with traditional ACIP piles extending to bedrock were not preferred. A mat supported on a limited number of ACIP piles, with the piles primarily acting as settlement reducers, was evaluated as the preferred foundation type. Traditional standard penetration test boring data was initially used to develop a numerical analysis of the soil-structure interaction using FLAC 3D software. The model was further modified with cone penetration and pressuremeter testing, along with actual load test results on several ACIP pile elements of varying lengths, but all tipping above bedrock. Through numerous project team discussions, and detailed numerical modeling analyses, ACIP piles were recommended for reducing mat foundation settlement. The process used advanced geotechnical analysis and design to mesh traditional mat and ACIP pile foundations into a unique soil-structure interaction based foundation system.

Large diameter, non-redundant drilled shaft foundations are becoming more popular in engineering and construction practice. When the drilled shaft diameters become large (generally 1.8-meter (6-foot) diameter or greater), mass concrete considerations need to be taken into account in the design and construction of these foundations. Mass concrete considerations due to the high heat of hydration are more acute in Hawaii because the local concrete mixes are very rich in cement content due to the angularity of the local crushed aggregates and the lack of cost-effective secondary cementitious materials (slag or structural quality fly ash are not readily available in Hawaii). Temperature measurements from several large diameter drilled shafts were taken in an effort to better understand the distribution of the temperatures in the constructed drilled shafts. In this paper, the temperatures at the center and edges of the drilled shafts and at various depths for several large-diameter drilled shafts are presented. The predicted temperatures from the finite element program compared well with the measured temperatures. Therefore, a discussion of the parameters used in the temperature predictions is presented.

The soils in the area of the Phoenix Sky Harbor International Airport (PSHIA) generally consist of alluvial sand, gravel, and cobbles (locally known as SGC) deposited by the Salt River. The conventional methods for axial capacity determination, which mostly come from experience with different types of soils, may not be appropriate for these ground conditions. An Osterberg cell load test was performed to obtain accurate site information on side shear and end bearing ultimate capacities of the drilled shafts. Comparisons were developed between predicted axial capacities of drilled shafts using several design methodologies, the axial capacity measured from static load testing, and the finite element method. Where high percentages of gravel and cobbles were encountered, the side friction was significantly underestimated by design equations commonly used. The load test results showed that underestimation of the side shear is evident; therefore design criteria, as well as the methods used for obtaining soil param., should be revisited.

The PHX Sky Train is an 8 km (5 mile) long automated people mover system located at Phoenix Sky Harbor International Airport. Phase I of the PHX Sky Train includes the design and construction of 227 drilled shafts supporting three stations and approximately 2,750 m (9,000 ft) of elevated guideway. The soil conditions in this area generally consist of alluvial sand, gravel and cobbles (locally known as SGC) deposited by the nearby Salt River. The foundation system will support relatively high axial loads, lateral loads and moments due to the height of the guideway above the ground surface, where it needs to pass over existing concourse walkways, bridges, a taxiway and buildings. The extreme design requirements, together with difficult ground conditions at the site, result in several challenges in the design and construction of the deep foundation system for the guideway and stations. Results from a full-scale load test were used to reduce the size of the drilled shafts. This paper provides an overall description of the PHX Sky Train project, a summary of the ground conditions, design requirements, load test results and construction methods used to successfully install the drilled shafts for this project.

The contemporary state-of-the-art analysis and design of piles and pile groups for tension neglects the compressive load imposed by superstructure on the pile foundation. The results of an experimental investigation on model single piles and pile groups embedded in a uniformly graded medium dense Indian Standard Sand, grade-2 (Ennore sand) poured to a desired density by pluviation were reported. The piles were tested under pure compressive and pure tension, as well under predefined combinations of the two. The experimental results were analyzed for various parameters such as net tensile capacity, efficiency of pile group, unit skin friction and their variations. Net tensile capacity decreased with increase in compressive load. The highest efficiency of pile groups under combined loading (Tension and Compression) was observed at 25% compressive load and mostly at 6d pile spacing.

A semi-empirical procedure was developed for analyzing the effect of compression on tensile response of pile groups based on the concept of interaction factor and the experimental results on model single piles and pile groups embedded in a uniformly graded medium dense Indian Standard Sand. Correction factors for tension, pile shape and limited depth of soil media were suggested, which were applied to the basic interaction factors for compressive loads to make them applicable for tensile load. Using the principle of superposition, the method of analysis for two-pile group was extended to predict the efficiency in tension for four- pile groups. A semi-empirical formulation was derived for percent decrease in interaction factor due to compression. Results obtained from the developed predictive model were compared with the experimental studies conducted by the author and the analytical results were in good agreement with experimental findings. The highest efficiency in tension for almost all the cases was obtained at 25% compressive load and the lowest at 100% compressive load.

The demand for off-shore pile installation in the Arabian Gulf has, over the last two decades, experienced unprecedented boom, triggered by the construction of platforms, to help facilitate the production and transport of oil and gas. Available borehole data show that ground conditions for pile installation in the offshore is highly variable, resulting in misassessment of insitu conditions, leading to large discrepancies between ultimate pile capacities, based on design, and actual capacities after installation. This paper uses pile installation records derived from platforms in the offshore of Qatar, the Gulf Region. More specifically, the paper evaluates "as-installed" ultimate capacities and safety factors, recommends remedial installation procedures, and proposes a means for determining pile acceptability for piles meeting refusal short of design penetration. The paper offers relevant recommendations to guide the design and installation of offshore structures; enabling the region's geotechnical community to solve their current pile installation problems and gain a margin of confidence regarding the ultimate capacity of installed piles.

This paper presents 24 test results on instrumented hollow tubular aluminum close ended floating piles in laboratory to examine the mechanisms of load transfer between the piles surface and normally consolidating marine clay. Hollow aluminum tubes of 32mm external diameter and wall thickness of 1mm and length to diameter ratio of 10, 20 and 30 were used as model single piles. Compression and pullout tests were carried out at time periods of 0 to 6hr, 0 to 12 hrs, 0 to 18 hrs and 0 to 24hrs from the time of installation. Multiple neutral planes are observed along the depth of the pile, which is contrary to the present understanding of load transfer. The variation of skin friction with respect to maximum shear strength of soil in undrained condition is about 10 to 200 %. Design stipulations have been proposed based on model tests findings.

A recent Minnesota Department of Transportation bridge project was outfitted with two in-place inclinometers and a series of strain gages on two driven piles to measure the change in strain, and associated stress, as consolidation settlement occurred in cohesive soils below newly placed bridge approach embankment fill. The magnitude of the downdrag acting on the piles, corrected for thermal effects, was monitored with respect to construction loading stages and nearby soil deflection. Downdrag loads of as much as 445 kN (50 tons) per pile were anticipated in the original design. Use of frequent data collection at this site, combined with the benefits of the construction sequencing - bridge loads were applied well after the construction and short-term surcharging of the embankment fill occurred - has offered additional insights into pile behavior in a downdrag environment. The paper discusses some aspects of the data collection and observed time-domain behavior of a selected gage location over a year-long observation period. A more comprehensive case history of this project, including overall pile behavior, and an investigation of the effects of the use of `pile sleeves' and live load dynamic response is in development for future publication.

A method of analysis is presented based on the three dimensional modeling of a pile/pile cap foundation with the computer program Plaxis that allows the reproduction of construction and loading phases for the structure. A construction phase is recommended that allows for the mobilization of a bearing pressure under the pile cap. This phase is defined as one during which construction dead loads are applied. During this phase, the pile cap is disconnected from the piles. In the subsequent phases, the piles are connected to the pile cap and the remaining design loads are applied. The analysis determines the loads on the piles and on the soils at the bearing level of the pile cap. Loads transferred to the soils at this level reduce the number of piles required to support the foundation resulting in significant savings in time and cost of construction.

The near surface, highly weathered limestones of the state of Qatar have complex lithologies attributable to post depositional changes that have altered hard rocks into soils and carbonate soils into a rock matrix. The matrix often clayey, sometimes cemented (with gypsum, anhydrite, and /or calcite) is not a rock nor could be considered as a soil per se. These deposits are: difficult to sample; extremely variable in composition and properties; and are susceptible to degradation, particularly when wet. The paper presents typical geotechnical information from selected sites where these deposits have been encountered. Plate load test data, carried out to predict settlements, are shown. Arrival at appropriate foundation geometries and allowable bearing capacities, consistent with field conditions, are noted. For the present, design of shallow foundations along the coast of Qatar has remained empirical and dependent upon site-specific information aided by judgment, local experience, and plate load test results. Moving forward, and thus reducing uncertainty in design of shallow foundations, requires long-term commitment to: i) proper analysis and scrutiny of appropriate field data, ii) modeling of soil/rock behavior, and iii) arrival at "well thought out" guidelines to help practitioners overcome the difficulties when designing shallow foundations.

One potential way to prevent overturning and increase efficiency of an eccentrically loaded footing is to hold the back of the footing down into the ground with a structural member such as a cable. A previous numerical analysis by the authors showed that under a specific condition by assuming a linearly elastic soil, a simplified model could be developed based on the elastic cracked concrete beam model to estimate soil stress distribution under the restrained and eccentrically loaded footing. In practice, however, soil has a limited shear strength, which is often described using the Mohr-Coulomb failure criterion. Under eccentric loading, the soil may yield near the edge of the footing.

The main criteria for safe performance of machine foundations subjected to dynamic loads are to control excessive displacements that depend on the resonance condition attained by the foundation-soil system. Several factors such as: dynamic properties of soil supporting the foundation, static weight of the foundation and vibrating equipment, area of contact of the foundation with soil, static soil pressure, nature and magnitude of unbalanced force have major influence on its behavior. The nature of dynamic loads and non-homogeneity of soil make the analysis and design of foundation subjected to dynamic loads to be more complex. The main objective of this paper is to present a parametric study on the influence of the rigid base on the response of the foundation-soil system. It stresses on the importance of accounting for the presence of rigid surface such as a shallow rock beneath the soil in the design of machine foundations.

Theoretical solutions are available to estimate ultimate undrained bearing capacity of shallow strip footings over saturated soft soil limited by a firm layer, such as bedrock. However, bedrock is often inclined with a dip and a strike. The influence of the bedrock inclination on bearing capacity of shallow foundations is not well understood. In this study, a 2D numerical method incorporated in FLAC 2D software was adopted. The soft soil was modeled as a linearly elastic perfectly plastic material with the Mohr-Coulomb failure criterion under an undrained condition. The footing was considered rigid and the load was applied by a velocity until the failure of the foundation. The influence of the inclined bedrock on the bearing capacity of the shallow strip foundation was investigated by varying the minimum depth-to-width ratio (i.e., the minimum depth of the soft soil to the bedrock/the width of the footing) and the bedrock inclination (assuming the dip perpendicular to the direction of the strip footing). Based on the numerical results, bearing capacity factors were modified with the inclination angle and depth to the bedrock. It is shown that an increase of the inclination angle and/or depth to the bedrock reduced the bearing capacity of the foundation.

This paper studied the effect of embedment on the ultimate bearing capacity of rigid strip footings embedded in two-layered clay soils with relatively different shear strengths. The ultimate collapse loads were calculated using the finite element method. A parametric study was performed for a relative depth of embedment D/B varying from 0 to 1 (where D and B are the footing embedment and width respectively), relative thickness of the top clay layer H/B from 0.125 to 4, and strength ratio of the two clay layers c_u1/c_u2 from 0.5 to 7, where c_u1 and c_u2 are the undrained shear strengths of the upper and lower clay layers respectively. The finite element results were presented in terms of a modified bearing capacity factor that accounts for the footing embedment and the relative shear strength and thickness of the two clay layers. The finite element results for surface strip footings and embedded footings in homogeneous clay were within the narrow ranges defined by the rigorous lower and upper bound solutions available in the literature. The finite element results for embedded footings were compared with those obtained using approximated bearing capacity equations for two-layered clay soils. The paper also described the changes in the type of the collapse mechanism as the footing relative depth of embedment (D/B) and relative layer thickness (H/B) vary as functions of the strength ratio (c_u1/c_u2) of the two clay layers.

A new primary crusher was built next to an existing crusher as part of a copper mine expansion in the Chilean Andes. Because the site is topographically constrained and elevations exceed 3,000m, only limited subsurface investigation was possible. Geotechnical characterizations of the soil and rock horizons were developed using information from this investigation and a previous investigation performed for the existing crusher. The natural soils are mainly Colluvial sandy/silty gravels overlying bedrock. Some fill was placed during previous construction. Portions of the existing natural soils had to be undercut and structural fill placed beneath the new, roughly 22m x 22m, crusher foundation. Additional areas were filled to establish a level platform for constructing a 25m high mechanically stabilized earth (MSE) wall adjacent to the new crusher. The wall provided a higher platform from which mine trucks could dump large materials for crushing. The effects of the MSE wall on the behavior of the new crusher foundation were analyzed to estimate settlements and anticipate possible rotational movements. These were particularly sensitive issues because they were excessive for the existing crusher. Topographic records of foundation settlement during MSE wall erection and crusher assembly indicate that performance satisfied the design criteria.

In the present study, an attempt has been made to model the seismic response of two perfectly rough embedded square footings placed in close spacing on layered soil deposit resting on strong bed rock by using the explicit finite difference code FLAC^3D. The footings carry equal static load without violating the ultimate bearing capacity under static condition. The soil is assumed to follow Mohr-Coulomb failure criteria with non-linear failure envelope. The results are presented in terms of horizontal x-acceleration response on the top of the footing, and the settlement of footings under seismic condition with the variation in clear spacing between two footings. The present theoretical investigation indicates that the settlement of closely spaced footings under seismic condition is found to be higher than that of single isolated footing.

Performance monitoring of structures is an important aspect of geotechnical engineering that routinely is overlooked. All too often once the geotechnical report is written and submitted to the client, the geotechnical engineer is not involved further in the project unless there is a problem. In many cases of unsatisfactory performance involving geotechnical engineering, the problem is generally related to structure settlement. This paper presents the results of long-term settlement monitoring of several moderately- to heavily-loaded structures located in the southeastern United States (SEUS). The structures bear on typical Coastal Plain sediments and have had ongoing settlement monitoring programs. Comparisons of predicted and measured settlement are made and recommendations for future settlement prediction on similar soils are given.

A new approach to assess the load-settlement-bearing capacity behavior of shallow foundations is presented in this paper. The load—settlement method accounts for the non-linearity of soil stress-strain behavior where as the majority of the settlement calculation methods in the literature assume linear stress-strain relationship which results in the inaccuracy of settlement calculation. The basic inputs of this method include the footing's geometric data such as footing width (B), length (L) and depth (D), and supporting soils properties including shear strength parameters, the soil's unit weight above and below foundation level to a depth of (D+B) and the strain at 50% stress level. It employs the stress-strain relationship developed by the senior author and transforms it to a load-settlement behavior. This new method has been verified against load tests performed on concrete footings in Texas, USA and provided a good agreement with the actual loading tests.

Due to the space constraint, sometimes new construction activities have to invade into the footprints of existing structures. An example is that the planned piles to support new superstructures are in conflict with the footprints of existing bridge abutment footings, or vice versa. As a result, the footings have to be re-evaluated for their settlement to consider the influence of piles. As a dilemma, there is no method taking the influence into account. In this study, a numerical approach was adopted to investigate the influence of the new pile on the settlement of the existing footing (Application 1) and also the influence of the existing piles on the settlement of newly constructed footing (Application 2). FLAC was employed in this study. The pile and footing were simulated as elastic material with appropriate properties. Subgrade soil was modeled as elastic material. Firstly, the simulation was carried out for a pile and a footing separately and the results were compared with theoretical solutions serving as model calibration. Then the simulation was carried out to exam the influence for both applications. For each application, various conditions were investigated including different footing load, footing size and pile load. The results were compared and discussed.

Several alternatives were evaluated for improving the load carrying capacity of the existing spread footings at a 1-story 9,100 square meter (98,000 square foot) manufacturing facility in Yonkers, New York. Improvements were deemed necessary because a proposed vertical building addition, consisting of 2 additional levels of parking/office space was planned, and because the underlying soils beneath the existing footings consisted of loose to dense sands/silts. Improvement alternatives that were evaluated during design included the installation of micro-piles, jet grouting, and increasing the size of the existing spread footings by forming and pouring symmetrical footing extensions. This latter alternative was determined to be the most cost effective by the Developer/Contractor for limiting the total estimated settlements under the existing and proposed loads to acceptable levels. Because the estimated footing settlements were dependent upon the assumed engineering properties of the underlying sands/silts, specifically the Modulus of Elasticity, E_s, an instrumentation plan was developed to allow the footing load and settlement response to be monitored in the field during construction. This "Observational Approach" was employed to better estimate E_s and the total footing settlement at completion.

Tests using thermocouple embedded in concrete cubes and embedded in the circulating liquids in the model thermopiles were used to identify the most suitable concrete mix and circulating fluid for energy piles. Three concrete mix designs were prepared for comparison. The sample cement mix contained a) 100% Portland cement b) Portland cement and pulverised fly ash and 3) Portland cement and ground granulated blast furnace slag. Water, glycol solution and a saline solution were tested for their thermal properties on each sample concrete mix. Temperature recordings were taken until equilibrium was achieved and data was analysed giving concluding remarks and recommendations.

The behavior of a pile subjected to thermo-mechanical loadings was studied in situ with the aim of quantifying the thermal influence on the bearing capacity of heat exchanger piles. A pile situated in a building under construction was equipped with a channel system to inject heat into it using a special heat pump. Load cells, deformation gauges and thermometers were installed to evaluate the behavior of the pile during seven tests with coupled thermomechanical loadings. The temperature variations applied to the pile were on the order of 15°C, and the mechanical load reached 1300 kN. The results obtained permitted the quantification of three significant effects brought about by the temperature increase: i. pile uplift, ii. mobilization of side friction due to the relative displacement of the pile with respect to the ground, and iii. additional load generated in the pile by constrain of the thermal stains.

The average residential retail price of electricity in the United States was 11.33 cents per KW-hour in 2009 which shows a 6.5% increase per year since 2007. The average price of electricity in the US is expected to increase to 15.93 cents per KW-hour by 2015. Florida ranks nationally among the top 5 states in the amount of energy consumed per capita. Even with substantial lifestyle changes, conservation, and energy efficiency improvements, global energy demand is likely to more than triple within next fifty years. Closed sanitary landfills have been developed for different purposes. Although most closed landfills have been developed as open areas and public parks, a number of closed landfill sites have been used for a range of beneficial uses including building sports complex, storage facilities, and shopping malls. Recently, a number of closed landfills have been considered for use as potential sites for renewable energy generation (i.e., from wind or sun). Foundation-cap compatibility is one of the critical factors that must be considered when planning the final site use for closed landfills as power parks. This paper evaluates the compatibility requirements for foundation design for installing solar energy capture systems on closed landfills. Potential challenges associated with foundation design and requirements for support equipment/structures are evaluated. Landfill characteristics and design considerations for controlling leachate and gas generation as well as management of vegetation on closed landfills were evaluated for different types of foundation structures. Technical analyses were conducted to assess the site closure and development needs for suitability of closed landfill sites and necessary foundation requirements for capturing solar energy. Landfill cap design features, wind and snow effects on solar panels, slope, and landfill settlement were evaluated.

This paper relates to an ongoing study on the impact of coupled thermo-mechanical loads on geothermal energy piles. This preliminary study evaluated the performance of laboratory scale energy piles embedded in silica soil. The laboratory scale model pile was subjected to a thermo-mechanical load to investigate effects of temperature on its shaft friction resistance. Testing of the model pile was carried out at different vertical stress levels, temperature gradients and heat exchanger modes. It has been found that the temperature is an important factor which influences the pile load capacity.

Energy Piles present an efficient solution for long-term carbon emission reduction and sustainable construction. However, they have received only partial acceptance by the industry, because of concerns regarding the impact of cyclic thermal changes on the serviceability of energy pile foundations. This paper investigates the applicability of the hybrid load transfer approach to load-settlement analysis of single piles behavior during thermal energy exchange processes. Back-analysis results in terms of the thermal and mechanical response of energy piles show good agreement with field test results from Lambeth College in London.

Geothermal Energy Piles (GEP) are an innovative renewable energy technology designed to access and exploit the relative constant temperature of the ground for efficient heating and cooling of buildings. In this paper, the design issues and operational considerations of GEPs are discussed, and their basic processes and mechanisms summarized. The controlling factors, such as the properties of the circulation fluid, flow rate, soil type and pile material are also discussed. A series of numerical analyses were performed to investigate the heat exchange behavior of GEPs for a variety of operational conditions. Based on these analyses, recommendations are drawn on practices which promote the most efficient GEP operation.

With one of the highest energy dependencies in the European Union, Ireland must adapt quickly to renewable energy technologies or risk paying the penalty in the form of high energy prices in years to come. Escalating energy costs have led to a renewed interest in alternative energy technologies and ground source energy is one such resource which is being increasingly considered. This paper presents some of the practical considerations of energy foundations, evidenced from the installation of a number of test energy piles. In addition, a preliminary feasibility study of an energy foundation system for a planned university administrative building and an overview of the current status of ground source energy technology in Ireland are presented. Building heating and cooling loads are estimated based on high building energy standards which the university hopes to implement in all building projects going forward. The proposed energy foundation system is shown to have the capacity to provide the heating and cooling base loads for the building.

There is currently a lack of established calculation method for the geotechnical design of heat exchanger piles. Thermo-mechanical effects are ignored and large overall security factors are therefore applied. This paper presents a new geotechnical numerical design method for heat exchanger piles, based on the load transfer approach. The method is validated on the basis of two in situ measurements. It is shown how the pile design could be adapted and optimized with respect to concrete resistance and the mobilization of the pile shaft friction during the operation of the heat exchange system.

A clear understanding of heat transfer through soil is important in the design of a thermal-active ground structure such as a geothermal energy pile. Thermal conductivity is an important material parameter for the design of such ground structures. In the work described in this paper, the thermal conductivity and volumetric heat capacity of a basaltic clay was investigated through laboratory studies using a thermal needle probe. The experimental results were analysed to examine the effects of dry density and moisture content on the thermal conductivity and volumetric heat capacity of the soil. Finally it was found that the thermal conductivity and volumetric heat capacity increased with higher moisture contents and dry densities.

Heat exchangers are currently being incorporated into drilled shaft foundations so that the same building materials can be employed to improve the energy efficiency of heat pump systems and to provide structural support for the building. This study involves the measurement of the load-settlement curves of scale-model thermo-active foundations in a geotechnical centrifuge after heating to different temperatures before applying a building load. The measured curves were evaluated using a load transfer (T-z) analysis to provide a preliminary evaluation of the changes in side shear distribution with heating. Foundations heated to different temperatures then loaded to failure showed an increase in side shear proportional to the temperature change.

Thermal conductivity tests were performed on three auger pressure grouted piles, both individually and as a group. These piles were installed with geothermal pipes used for closed loop geothermal heating and cooling applications. Installing pipe loops in piles allows geothermal energy captured from the ground to be transferred using heat pumps to heat and cool buildings. This technology provides both a renewable energy source and a cost effective option compared to other geothermal and conventional methods. The results of the group test are compared to the individual pile results at a site with a soil profile consisting of sand and clay through the depth that the piles were installed. Measurements of the pile temperature, circulating water temperature, and ground temperature in the center of the pile group for the week long group test are presented. The thermal conductivities for all cases are calculated using line source methods. An example energy pile design for a two story office building supported on these piles is also presented.

A full scale instrumented trial embankment test was conducted to evaluate the effects of the Rammed Aggregate Pier (RAP) System on the very soft clays underlying railway a proposed embankment test site in the island of Luzon, the Philippines. A 5.0m high trial embankment was on a Section of a 10 kilometer stretch of railway on relatively very soft marshy ground to simulate embankment loads and the impact of train loads on railway embankments of the NORTHRAIL Railway. The study was initiated to prove that consolidation time in very soft clays could be accelerated by the lateral prestressing and prestraining effects of the rammed aggregates piers on the subgrade and the enhanced drainage effect of the RAP body. This paper discusses the test embankment construction, instrumentation and monitoring and the geotechnical exploration to gather soil parameters. The theoretical settlement calculations and field observations served as the bases for the findings reported. The results of the settlement monitoring program revealed that significant time savings could be realized during railway embankment construction if the RAP System is utilized, because time to full consolidation was accelerated to four (4) weeks instead of the calculated 6 to 8 months using other conventional ground improvement systems.

Dynamically compacted sands exhibit a drop in cone penetration resistance immediately after compaction, but a gradual increase in the resistance occurs in a matter of weeks and months. An explanation of this phenomenon is suggested, based on the process of stress corrosion cracking of the micro-morphological features on the surface of the sand grains at the contacts. This process, also referred to as static fatigue, leads to a change in the macroscopic elastic moduli of the sand, which, in turn, causes an increase in the macroscopic horizontal stress under one-dimensional strain conditions. Consequently, delayed increase in the horizontal stress leads to the time-dependent increase in the penetration resistance of the sand bed.

The deep dynamic compaction technique has been implemented with success in a large range of soils including municipal solid waste (MSW). The results of a systematic study on the effectiveness of the technique on MSW sites through 64 case histories are presented. The results suggest that the depth of improvement is typically smaller in MSW compared to cohesionless soils. Also, the induced settlement is significantly affected by the applied energy and varies from 5% to 25% of the thickness of the MSW.

Encasing a granular column with a high strength geosynthetic significantly decreases its lateral displacement and effectively enhances the load carrying capacity of the column. This paper describes the results of three-dimensional finite element analyses that were carried out to simulate the behavior of a single geosynthetic encased column in soft clay using the Mohr Coulomb, extended Drucker-Prager, and Single Hardening constitutive models for the encased granular soil. Existing triaxial test results for loose and dense sands were used to calibrate the constitutive models that were examined in this study. Numerical results show the importance of selecting a constitutive model that accurately captures the volumetric strain response of the encased granular material during application of axial load to the column.

Vibro-replacement stone columns installed using the dry method have been used to support embankments constructed on soft clay for a highway upgrade project in Australia. The main alignment of the upgraded highway is close to some existing structural piles. An estimate of the lateral soil displacements at the pile location was required to assess any impact on the piles prior to stone column installation. Therefore a field trial has been performed to assess the lateral displacement caused by the stone column installation at various distances from the centerline of the stone column. The measured displacements were then compared with the results from theoretical cavity expansion solutions. The results of the trial showed that the lateral displacements vary approximately inversely with distance from the column and that the magnitude of the displacements can be approximated using theoretical cavity expansion solutions.

Trestle Glen is a mixed-use, mixed-income, transit-oriented urban reuse development on 6,880 square meters (1.7 acres) that now offers 119 units of affordable housing along with commercial and light industrial options adjacent to the Colma Bay Area Rapid Transit (BART) Station in Colma (San Mateo County), California. Subsurface soil at the Trestle Glen site includes artificial fill over potentially liquefiable, loose- to medium-dense silty to clayey sands, as well as soft silts and low-plasticity clays, extending to depths of about 7.6 to 9.1 meters (25 to 30 feet) locally along the historic creek alignments in the southeastern portion of the site. Groundwater is approximately 3.4 meters (11 feet) below the ground surface in this portion of the site. This paper presents a case study of the use of impact rammed aggregate piers (RAPs) to mitigate potentially liquefiable soil. The RAP system is a proprietary ground improvement method that involves driving a 30-centimeter (12-inch) diameter hollow mandrel with a 40-centimeter (16-inch) diameter rammer foot to the design depth. The hole is then backfilled with open-graded aggregate that is vibrated in 0.3-meter (1-foot) lifts by a dynamic impact hammer. This paper includes the results of a pre- and post-ground improvement Cone Penetration Test (CPT) program implemented to evaluate the post-ground improvement liquefaction and seismic settlement potential.

Partially penetrating prefabricated vertical drain (PVDs) with a combined surcharge and vacuum preloading are considered in this paper. The analysis results can be used in cases where the soft soil clay is too deep and not economical to be penetrated to full depth, or the surcharge preloading is too small to justify full penetration of soft clay layer or the vacuum pressure can be lost, which is caused by the permeability of the bottom of the clay for the fully penetrated drain etc.. In this model, a virtual vertical drain is assumed to reflect the real three-dimensional seepage in the soil beneath the tip of PVD instead of using the traditional one-dimensional consolidation theory, and at the same time, the well-resistance and the smear zone can be also considered. The vacuum pressure distribution is assumed to be no loss along the drain, whereas a zero pore pressure boundary condition is assumed at the interface between the bottom clay layer and the lower drainage layer. The proposed solutions are then employed to analyze a case history.

Deep Mixing is widely used in Singapore and other countries all over the world. Due to the non-uniformity of the mixing, the strength of the deep-mixing improved soil is often highly variable and this has been a problem in practice. Two projects in Singapore using DM in ground treatment for Marina Bay Financial Centre (MBFC) and new Nicoll Highway MRT Station (NCHS) are introduced and statistical analysis is performed to study on the variation of the unconfined compressive strength of the deep mixing column samples from these projects. The results indicate that the sample COVs lie in the range suggested in previous literatures. With enough statistical sample size, samples from the same operating parameters show similar trend in their histograms. Moreover, the geological conditions and operating parameters considerably affect the mixing quality. The data show that the design unconfined compressive strength of the deep mixing columns is conservative.

The seismic behavior of pile foundations in soft clays is a very complex problem with interacting piles, soils and superstructure. Using ground improvement, for example, Cement Deep Soil Mixing (CDSM), to restrict lateral displacements of piles during earthquakes is a viable, but not fully explored technique. This paper presents experimental methods and procedures for centrifuge tests on single piles with and without ground improvement under both static and dynamic loadings. The data collected from the centrifuge test were used to analyze the differences between piles in unimproved and CDSM-improved soft clay. The test results confirmed that the CDSM can improve the seismic behavior of pile foundations and demonstrated that the pile response is directly related to the size of the ground improvement zone.

This research study aims at investigating the scale effect of shallow foundation on reinforced soils using finite element analysis. The finite element model was first verified by the results of laboratory model footing tests, and then was used to numerically investigate the load-settlement response of different footing sizes on reinforced soil foundations. Two different soil-reinforcement interface models were studied and three different reinforcement configurations were examined. The results of finite element analyses indicate that the scale effect of reinforced soil foundation is mainly related to the reinforcement ratio (R_r) of the reinforced zone. The difference in the bearing capacity becomes negligible as long as the reinforcement depth ratio (d/B) and the reinforcement ratio (R_r) of the reinforced zone remain constant for all footing sizes.

As a new solid-liquid separation technology, electro-osmosis has many advantages such as high drainage rate, the convenience and flexibility of operation. However, high energy consumption limits the application of electro-osmosis. Many experimental studies have shown that it can effectively improve the intensity of the soil and give lower moisture content when using the vacuum preloading and electro-osmosis simultaneously compared to only using one of the two methods. In this paper, two analytical models are developed. One is the one dimensional model of vacuum preloading binding with electro-osmosis, another is one dimensional axisymmetric model of vacuum preloading binding with electro-osmosis. The theoretical solutions of the two models are derived, and numerical FEM models were also developed to compare with the theoretical results. From the results, we can see that the theoretical solution is highly compatible with the numerical simulation. The pore pressure and displacement distributions in the model are also presented.

The work presented in this paper explores the effects of drainage and rate of loading on the load response of soft clays that are reinforced with sand columns. The inclusion of sand columns in soft clays has been widely used to increase the load carrying capacity of the clay, reduce the settlement, and control/reduce the generation of excess pore water pressure during loading. A comprehensive laboratory testing program was designed to further explore and quantify those effects. It consists of a series of consolidated undrained (CU) and consolidated drained (CD) triaxial tests conducted on specimens of Kaolin clay reinforced with sand columns of various diameters. The clay specimens had diameters of 7.1 cm and heights of 14.2 cm and were prepared from slurry. The sand columns had diameters of 2 or 3 cm and were installed in pre-drilled holes fully penetrating in the clay specimen. Tests were conducted at effective confining pressures of 100, 150, and 200 kPa. Results obtained from the laboratory testing program are presented and the effects of the various parameters which govern the load response of the sand column/clay composite are presented and discussed.

Often times when a project site exhibits poor subsurface conditions not suitable for foundation support the most logical solution is a deep foundation system supported on/in an underlying dense/hard stratum. However, in some instances ground modification associated with shallow spread footings can be a more cost effective solution. Compaction grouting is an extremely flexible and customizable approach that can be applied to numerous poor subsoil conditions to stiffen and densify the subsoils to a desired degree applicable to the proposed construction. Compaction grouting is not a new technique; its application in areas of Karst geology where acute subsurface stabilization is necessary has been effectively used in many instances since the early 1950's (Warner 2004). Subsurface erosion in Karst areas is prevalent in an area of eastern Pennsylvania that spans from as far west as Shippensburg through Lancaster, Reading, and Allentown to the eastern border in Easton. Two case histories are presented — one involves "stiffening" the foundation subsoils encountered beneath additions to an existing 2-story structure in Millersville, PA. The second case history is the improvement of soils impacted by a water main break in Bethlehem, PA. These case histories describe subsurface conditions that compaction grouting was applied to and the methods used to ensure a successful grouting program. Also discussed are real time field results used to modify the compaction grouting program and monitor its effectiveness. Full-time monitoring was provided throughout the field work on each project.

Several vacuum preloading systems have been developed over the years. Each has its advantages and limitations. Two vacuum preloading techniques, namely the Menard and the Beaudrain systems, have been evaluated using model tests. Comparison between using two different drain types, circular and band drain has also been conducted. The test results are presented in this paper. The model tests show that the Menard preloading system is more effective under the test conditions; on the other hand, not much difference is observed between the consolidation results of the circular and band drain. The implication of the model tests to large scale field conditions is also discussed.

Series of repeated load isotropic triaxial compression tests were carried out on rural road subgrade material (with and without fiber reinforcement) under unconsolidated undrained conditions to study the accumulation of permanent strains with loading cycles. Influence of number of loading cycles, deviatoric and confining stress levels, and fiber reinforcement on the accumulated permanent strains of subgrade material were studied. Tests were conducted on reconstituted local Roorkee clayey soil samples, which were reinforced with randomly distributed fibers (coir and polypropylene) at optimum content. Test results were analyzed to address the influence of above said variables and were compared with the un-reinforced one. It is observed that permanent strain behavior decreases with increase in confining pressure but increases with increase in the number of load cycles and cyclic deviatoric stress application. The reinforcement effect (resistance to permanent deformation) is found to increase appreciably when mixed with clayey soil. Coir fiber showed a higher resistance than polypropylene fiber. With the above mentioned finding it may be concluded that coir fiber can be used effectively in rural road subgrade.

It is known that increased swell in soils with alkali solution can occur due to either increased cation exchange capacity and/or due to mineralogical changes. In the recent past lime is known to effectively control alkali induced heave in kaolinitic soils. Thus the efficiency of lime to produce pozzolanic compounds which aid in binding of soil particles increases in alkaline condition. In the search of cost effective pozzolanic materials to control the alkali induced heave, fly ash has gained due attention. Fly ash can be used if it is resistant to alkali and does not produce compounds that cause undesirable swelling. The paper attempts to understand the effect of different concentrations (1M, 2M and 4M) of sodium hydroxide (alkali) solution on the swelling and compressibility of fly ash. The results clearly indicate that no swell is observed with any concentrations of alkali solution even after allowing the samples to interact with alkali solution for longer duration. X-ray diffraction and SEM studies reveal that the pozzolanic compounds that form in fly ash due to alkali interaction can help in inhibiting the swelling. Thus fly ash seems to be a promising material to control the swelling in soils.

Recent discoveries into how certain marine organisms produce their skeletons has provided inspiration for a new treatment method for creating cementation in both fine and coarse-grained soils. The silicification method offers environmental and physical advantages over some traditional methods by utilizing non-toxic, commercially available components with low potential for adverse environmental effects. Silicification begins by first pretreating the soil using a commercially available cationic polyelectrolyte which is then followed by treatment with a mixture of commercial sodium silicate and buffer. The unconfined compressive strengths of three sands and one clay were measured over a range of polyelectrolyte concentrations at a constant sodium silicate concentration of 20 percent by volume. Results indicate that polyelectrolyte type and pretreatment concentration can be optimized to significantly increase the compressive strengths of sands and clays. Review of published data suggests that compressive strengths of samples silicified by this approach are equal to or greater than strengths of samples prepared at comparable silicate contents using a variety of methods.

The undrained shearing properties of sand permeated with bentonite suspensions are studied to investigate the use of bentonite suspensions for static liquefaction mitigation. Rheological tests are performed to evaluate the penetrability and the thixotropic strength recovery of the suspensions. The results show that the initial viscosity and the yield stress are reduced significantly by adding 2% sodium pyrophosphate (SPP) to 10% bentonite suspensions. Moreover, the yield stress and the viscosity gradually increase with time due to the thixotropic nature of the bentonite suspensions. The shearing response of the permeated soil is observed by consolidated undrained triaxial tests on loose Ottawa sand specimens permeated with bentonite suspensions. The stress-strain response of the permeated specimens shows no drop in stress after the undrained instability state as compared to the response of clean sand specimens. Additionally, the undrained shear response of the permeated sand specimens displays no cohesion and the same friction angle as clean sand. This indicates that the sand fabric is relatively unaffected by the pressures applied to permeate the bentonite suspension. It is concluded that the permeation of bentonite suspensions could be an effective method of soil improvement for static liquefaction prevention in loose saturated sands.

In this experimental study, changes in the viscosity, setting (gelling) time and the curing temperature of an acrylamide chemical grout with and without a cationic-surfactant were investigated. Also the influence on the pull-out strength of the grout and grouted sand and compressive strength of the grouted sand were investigated. Cetyl trimethyl ammonium bromide (CTAB) was used as the cationic surfactant. The weight of the surfactant was varied from 0.5 grams to 4 grams per 100 grams of grout mix. The gelling time tests were performed starting with different initial temperatures of the grout mix, varying from 40°F to 80°F (4.4°C to 26.6°C). Unconfined Compression tests were performed after the 7^th day of curing the specimen. The results showed that addition of surfactant did not have a noticeable effect on the viscosity of the grout solution. It was found that addition of 0.5% of CTAB increased the gelling time by 60, 75 and 15 seconds at 40°F (4.4°C), 60°F (15.5°C) and 80°F (26.6°C) respectively. Addition of 4% CTAB increased the gelling time by nearly 16785, 5715 and 1335 seconds at 40°F (4.4°C), 60°F (15.5°C) and 80°F (26.6°C). Noticeable changes were observed in the pull-out strengths. Addition of 0.5% and 4% of CTAB to the grout mix increased the compressive strength of the grouted sand.

This study describes the laboratory evaluation of the effect of freezing-thawing cycles on strength and swell potential of fly ash and randomly oriented fiber stabilized expansive soil subbases. Two high plasticity expansive clay soils were mixed with a Class C fly ash and artificial fibers, and then compacted to prepare specimens for all combinations for fly ash contents of 0%, 10%, and 20%, and a fiber content of 1%. After curing all specimens for seven days, the first set was subjected to unconfined compression tests, split tensile tests, and vertical swell tests. Similar tests were also conducted on another three sets of specimens after being subjected to 24 freezing-thawing cycles in a laboratory controlled environment. The freezing-thawing cycles significantly decreased the strength and increased the swell potential.However, the fiber inclusion minimized the potential for strength loss and swelling of expansive soil due to freezing-thawing cycles.

An experimental program was undertaken to investigate the effects of discrete polypropylene fibres and low dosage ordinary Portland cement (OPC) on the stress-strain and unconfined compressive strength behavior of clayey soil. Multifilament polypropylene fibre in three different lengths (6.0mm, 12.0mm, and 19.0mm) and two fibre dosages (i.e. 0.5% and 1.0% by dry weight of soil) were considered. At first, compaction characteristics of the untreated soil were evaluated at standard compaction energy. Using compaction characteristics of untreated soil 9 different fibre-cement-soil mixtures (i.e. fibre/soil-cement ratio of 0.5% and 1.0% and cement/soil ratio of 0.0%, 3.0% and 6.0% by dry weight) were composed, and their unconfined compression test were carried out after 1-, 7-, and 28-days curing periods. The obtained test results indicated that the effect of fibre dosage on the stress-strain behavior is superior to the effect of fibre length.

Scout Moor Wind Farm is situated in the West Pennine Moors in Lancashire, Northwest England. The site chosen for the 65MW wind farm is located on moorland which consists of extensive peat bog covering the majority of the site. It was also anticipated that very soft to soft glacial clays would underly a significant proportion of the blanket bog. It was anticipated that the vast majority of the site was underlain by extensive unrecorded shallow mine workings. These are just a few of the factors that required consideration when Scott Wilson Ltd. were commissioned as Lead Civils Designer in 2005 for the balance of plant works for the wind farm. The commission included conducting ground investigation and the detailed design of over 12km of access track, 26 crane pad construction areas, drainage and cable runs, 26 wind turbine foundations (2.5MW), and an electrical substation for connection in to the national grid. The solution to use a `floating road' construction for the access tracks, effectively a linear load transfer platform, took into consideration the various site constraints as well as issues including construction buildability, design life and economics which all played a significant role in the decision. This paper is concerned with the principals of the design philosophy for the use of geogrid reinforced unpaved access tracks and bridged mine voids, and the use of geogrids and the elements of the detailed design methodology used to overcome the challenges set out by the moorland environment.

Interchange 16W of the New Jersey Turnpike is located within a region generally referred to as the Hackensack Meadowlands. The former glacial Lake Hackensack is characterized by post glacial deposition of deep (between 24.4 to over 30.5 meters, 80 to over 100-feet) stratified silty clays and clays usually very soft and highly compressible. Due to the increased volume of traffic, partly due to the construction of a new NFL Football Stadium, Interchange 16W had to be reconfigured to improve traffic flow with Route 3 and the Meadowlands Sports Complex in East Rutherford, NJ. Embankment heights up to 10.4 meters (34 feet) were required for the new ramp configurations. Estimated settlement up to 1.3 meters (52 inches) was calculated. An extensive use of wick drains as deep as 37.8 meters (124-feet), high strength geotextile, two-stage MSE Walls, and surcharging placed in two phases were required to successfully construct the ramp embankments. Cutoff sheetpile walls and a monitoring program were incorporated to protect the existing embankments and roads from deformation. This paper will compare the actual results from an extensive field instrumentation program to the geotechnical design assumptions. The use of the field instrumentation program was critical to providing a successful finished project safely and on schedule.

In this paper, the finite element code ABAQUS was used together with Cam-Clay constitutive model for clays in order to achieve a better understanding of the behavior of cohesive soils under dynamic compaction (impact from a falling heavy mass). The finite element simulation techniques for modeling impact of falling weight on the ground surface and the numerical techniques for properly accounting for infinite boundaries in a half-space are described in the paper. The validity of the finite element modeling technique was provided by matching predictions with some of known empirical rules from observations and field measurements. Using the verified finite element model, a comprehensive parametric study was conducted, from which practical findings have been obtained concerning the depth of improvement as related to impact energy, as well as the densification contours as influenced by impact energy and soil properties. The horizontal extent of densification due to impact was also delineated through finite element simulations. This paper contributes to enhancing existing knowledge of dynamic compaction in cohesive soils through a detailed FE simulation study.

A smear zone, i.e., a disturbed zone is considered to form during installation of a prefabricated vertical drain (PVD) using a mandrel and this zone retards the horizontal consolidation of soft clays in the vicinity of PVD. The characteristics of the smear zone, such as its extent and hydraulic conductivity remain discrepant among investigators. This study attempts to determine the extent of the smear zone and to measure the hydraulic conductivity of the smear zone directly by laboratory tests. For this purpose, a Smear Zone Model (SZM) test is described. The tests indicate that two soil zones are identifiable in the soil mass surrounding the PVD after the PVD installation using the mandrel. The extent of the smear zone is about 3 to 4 times the equivalent radius of the mandrel depending on soil type. The smear zone permeability ratio was measured to be about 1.03 to 1.25 for the soils tested. However, the test conditions employed were least conducive to generating a highly disturbed zone.

The site for a new two-story classroom building was underlain by a 4.57 m thick layer of natural marsh deposit consisting of very soft organic clay. The specialty contractor provided a design-build solution of mass stabilization, a dry soil mixing technique, to increase the shear strength and decrease the compressibility of the organic clay insitu. This method allowed the structure to be founded on shallow spread footings without soil replacement or deep foundations. Total settlement of the building, on shallow foundations designed for an allowable bearing capacity of 192 kPa, was limited to 25.4 mm, with differential settlement on the order of 12 mm. Dry Portland cement was pneumatically pumped to a high-speed mixing tool mounted on track hoe arm. The clay and cement were systematically mixed insitu to proportions determined by a pre-production laboratory mix design program. Post-treatment testing consisting of laboratory Unconfined Compressive Strength, Cone Penetrometer and Column Penetration testing confirmed that the required strength was achieved. This paper presents the design, construction, and quality control testing of the mass stabilization program. A pre and post-treatment test data comparison shows the extent of the improvement of the treated soil. No significant settlement was measured during or after construction.

The paper presents design and construction aspects of a lightweight material embankment supported on timber piles through a geogrid reinforced load transfer platform in Orland Park, Cook County, Illinois. The pile supported embankment represented a feasible, durable and cost-effective solution for constructing the embankment on the low bearing capacity, high compressibility foundation soils encountered at the project site. The pile supported embankment technology uses conventional practice for all aspects of design, specification, and construction such that it can be readily implemented. Because of the very weak nature of the soils encountered at the project site, a stiff geogrid reinforced load platform was required between embankment and supporting piles. In order to reduce the loads on timber piles, expanded shale lightweight aggregate was used in the embankment and load transfer platform. Based on the estimated pile loads along the embankment and the available pile bearing capacity at various locations, the length of 10-inch tip timber pile with natural taper, spaced at a 7 feet center-to-center grid pattern varied from 40 feet to 60 feet. A pile concrete mini-cap, 3 feet by 3 feet, was placed on the top of the piles, which provided a clear spacing between individual supports of 4 feet. In addition to embankment design, the paper discusses PDA monitoring of piles during driving, settlement monitoring results and other challenges associated with the embankment construction.

This paper presents experimental results of the effect of Portland cement and Cement Kiln Dust (CKD) on engineering properties of soils from Aberdeen and Everett in the state of Washington. CKD and cement were added in several different percentages of dry weight of soils. Laboratory tests including Atterberg limits, standard Proctor and unconfined compressive strength were performed. Results of cement and CKD treatment are compared. Results of the investigation showed cement and CKD treatment led to an increase in optimum moisture content, and a decrease in maximum dry unit weight. It was also observed that the unconfined compressive strength and modulus of elasticity of CKD treated soils were lower than that achieved by cement treatment. However, CKD still can be used for soil stabilization purposes. In addition, this study presents experimental results of slope erosion control using CKD. A natural slope in Socorro, NM was divided into four different parts, and the surface soil of each portion was treated with 0, 5, 10, and 15% CKD by dry weight of the soil. Results of the soil loss of a small-scale CKD treated slope under rainfall simulator were compared with the soil loss of the full scale CKD treated slope in the field. The field slope was monitored for a time period of five months for soil loss, and soil loss was determined by surveying the slope surface within this time period. It was observed that soil loss decreased significantly as CKD content increased.

This paper presents experimental data on a well graded angular sand used to investigate the impact of particular design parameters such as sample density and sample height on the arching mechanism. Soil arching is a natural phenomenon which occurs in all granular soils as a result of stress redistribution. When the trapdoor at the base of the model was released the soil block above the trapdoor settled while the soil block above the supports did not thus shear stresses developed in the fill material between the yielding and unyielding zones. The base of the model was released at two speeds, rapid and gradual, to simulate consolidation of the soft subsoil between piles in a piled embankment and the formation of a sudden void. It was noted that the final load transfer recorded was the same for both the rapid and gradual tests, however there was an initial peak load transfer recorded for the rapid tests. The relationship between surface and base displacements recorded in the model are also discussed.

Design of geosynthetic-reinforced column-supported embankments requires calculation of the reduced load on the geosynthetic reinforcement due to arching within the embankment fill. The load on the geosynthetic reinforcement is then used to calculate the tension in the geosynthetic reinforcement of a given strength and stiffness. Russell and Pierpoint (1997) proposed a method for calculating the load on the geosynthetic reinforcement in column-supported embankments based on Terzaghi's (1943) theory of arching. Their expression is developed for square columns in a square arrangement with homogeneous embankment fill material. This method shows reasonable agreement with instrumented embankments and numerical results presented in the literature but is limited to specific column geometry and homogeneous fill. Other column arrangement patterns include rectangular, equilateral triangular, and isosceles triangular, and the columns themselves may also be round. Some column-supported embankment design methods also specify a select fill material at the base of the embankment prior to placing general embankment fill material in order to further promote arching. This paper presents a method for calculating the load on the geosynthetic reinforcement in column-supported embankments for generalized column and unit cell geometry and two layers of embankment fill with differing material properties and lateral earth pressure coefficients.

Surcharging to improve compressible soils was the most attractive foundation option for constructing new structures for a large scale expansion of a wastewater treatment plant in Virginia Beach, VA. This required tall and steep embankments in close proximity of existing operating plant structures and utilities. Such tall (up to 40 feet (12m) high) and steep (up to 4V:1H) embankments were designed as mechanically stabilized earth (MSE). A detailed geotechnical investigation was performed to adequately characterize the site stratigraphy and soil properties. A significant volume (over one million cubic yards) of temporary borrow material was procured from adjacent areas where it was returned after completion of the surcharge program which demonstrated sustainability in use of natural resources. A geotechnical investigation in the borrow area was also performed. A monitoring program was implemented to measure the vertical and lateral movements and pore pressures during the surcharging program.

This paper introduces current work in collating data from different projects using soil mix technology and establishing trends using artificial neural networks (ANNs). Variation in unconfined compressive strength as a function of selected soil mix variables (e.g., initial soil water content and binder dosage) is observed through the data compiled from completed and on-going soil mixing projects around the world. The potential and feasibility of ANNs in developing predictive models, which take into account a large number of variables, is discussed. The main objective of the work is the management and effective utilization of salient variables and the development of predictive models useful for soil mix technology design. Based on the observed success in the predictions made, this paper suggests that neural network analysis for the prediction of properties of soil mix systems is feasible.

A new kind of reinforced Deep Cement Mixing (DCM) pile namely; Stiffened Deep Cement Mixing (SDCM) pile is introduced to mitigate the problems due to low flexural resistance, quality control problem and unexpected failure of the DCM pile. The SDCM pile consists of a DCM pile reinforced with concrete core pile. Previously, a full scale pile load test and a full scale embankment loading test were successfully conducted in the field. To continue the study on the behavior of SDCM and DCM piles, the 3D finite element simulations using Plaxis 3D Foundation Software Version 1.6 were conducted in this study. The simulations of full scale pile load test consisted of two categories of testing which are the axial compression andthe lateral loading. For DCM C-1 and C-2 piles simulations were conducted for the clay-cement cohesion, C_DCM, as 300 kPa and 200 kPa as well as the clay-cement modulus, E_DCM, as 60,000 kPa and 40,000 kPa. For the SDCM piles, the simulation results show that increasing length ratio, L_core/L_DCM, increased the bearing capacity with small effect from the sectional area ratio, A_core/A_DCM, for the axial compression loading. On the other hand, increasing the sectional area ratio, A_core/A_DCM, significantly influenced the ultimate lateral resistance while the length ratio, L_core/L_DCM, has little effect on the ultimate lateral load capacity when the length of concrete core pile is longer than 4.0 m.

This paper addresses the soil-contaminant-water interactions in a high acid buffering soil during electrokinetic remediation. A one-dimensional transport model was developed to predict the transport and speciation of heavy metals (chromium, nickel, and cadmium) in high acid buffering glacial till soil during electrokinetics. The developed model assimilates geochemical reactions into electrokinetic transport modeling. The transport model incorporates: (1) presence of carbonates in soil; (2) adsorption of contaminants to soil surface; and (3) synergistic effects of multiple chemical species on contaminant transport during electrokinetic remediation. The model was validated with bench-scale electrokinetic experiments. The predicted pH profiles, electroosmotic flow, and contaminant distribution of chromium, nickel, and cadmium in glacial till soil during electrokinetic remediation were found to agree with the experimental results. The model also predicted the contaminant speciation and form (aqueous, adsorbed, and precipitated) in soil during electrokinetics. The model showed that chemical precipitation and adsorption are, respectively, the main fixation mechanisms for the cationic (nickel cadmium) and anioinic (hexavalent chromium) metals in glacial till during electrokinteic remediation. Overall, the model predictions allowed for an understanding of the transport and physico-chemical processes that control electrokinetic remediation of high acid buffering contaminated soil.

The Freeman's Bridge Road remediation project, Glenville, New York, USA, is an example of an integrated approach to environmental remediation. Onsite direct low temperature thermal desorption (LTTD) technology was used to treat non-hazardous contaminated soil, and indirect LTTD technology was used to treat hazardous soil. Treated soil was rendered suitable for beneficial reuse as onsite backfill. The use of dual onsite LTTD technologies at this site is a "first" in New York State, demonstrating a viable alternative to landfilling. Over 575 MN (65,000 tons) of hazardous and non-hazardous impacted soil were treated, improving environmental conditions, while also protecting the nearby scenic and historic Mohawk River, an important natural and recreational resource. This project demonstrates that it is feasible, with careful planning, to segregate and treat co-mingled waste streams. The direct thermal treatment technology proved successful in treating non-hazardous soils. Although the indirect thermal treatment system also proved capable of treating the hazardous contaminated soil, the presence of solid phase organic materials, such as roofing and asphalt, presented significant obstacles, which proved impractical to overcome.

Acidity generated from the oxidation of pyrite and other sulphidic compounds that exist at shallow depths in acid sulphate soils (ASS) presents a challenging environmental problem in coastal Australia. The generated acidic groundwater can adversely impact coastal ecosystems, aquaculture and agriculture. Groundwater manipulation using weirs and modified floodgates in creeks and flood mitigation drains in ASS-affected farmland, which has been practiced for over a decade for preventing pyrite oxidation, is not effective in low-lying floodplains due to the high risk of flooding. In this paper, the authors present an overview of their experience in coastal Australia, a critical evaluation of currently practiced geo-environmental remediation methods as well as a demonstration of a pilot permeable reactive barrier (PRB) to control acidic groundwater pollution. The selection of recycled concrete, a commonly available alkaline waste material, and the systematic investigation of its longevity are highlighted through a series of batch and column experiments. In addition, the improvement of the groundwater quality by a pilot PRB using recycled concrete in ASS terrain within the Shoalhaven region of NSW, Australia will be elucidated based on field data collected over the last 3.5 years.

Cleaning contaminated soil/groundwater is important to federal and state agencies. Traditional contaminant removal methods are costly and impractical for large sites. Less disruptive remediation techniques (e.g., air sparging) are attractive but limited by the restriction of airflow in soil. The use of electromagnetic (EM) stimulation to expedite airflow, diffusion, and control air channel formation is investigated. The diffusion of an inert dye as the diffusive matter within water and the effect of EM waves on the diffusion are experimentally modeled. To study the effect on air sparging through saturated soil, a clear acrylic box filled with a water-saturated glass bead medium and air as the diffusive matter is used. The effects of the electric field on air channel formation in the second case (i.e., glass-bead medium) are studied. It is expected that the stimulation of the water increases the diffusion of air between air channels and expands the air channel volume. The EM field is made possible using a dipole antenna connected to an RF source. The alternating electric field emitted off the antenna into the medium, oscillates the dipole water molecules. The stimulation helps enhance diffusion and enlarge the formed air channels.

Contamination of groundwater by dense nonaqueous phase liquids (DNAPLs) such as chlorinated hydrocarbons is an environmental concern in industrial and hazardous waste sites. The purpose of this study was to investigate the effect of a cationic biosurfactant and a biosurfactant to extract tetrachloroethylene (PCE) from contaminated soils and to degrade the PCE in-situ using surfactant-bimetallic colloidal solutions. Effectiveness of cetyl trimethyl ammonium bromide (CTAB) and UH-biosurfactant were compared to water in removing PCE from 100,000 mg/kg PCE contaminated soils using column studies. Fe/Ni nano-bimetallic particles were produced using the solution method and combined with the surfactant solutions to prepare the colloidal solutions. Desorption kinetics and adsorption isotherms for the two surfactants with the major constituents of soils have been quantified and used in the transportation modeling. The surfactant-colloidal solutions were effective in degrading the PCE and reducing the leaching of PCE from contaminated soil.

Organoclays are composites of alkylammonium organic cations that are electrostatically bonded to clay minerals. Organoclays have shown promise as sorptive media in a variety of contaminant containment applications; however, many of their fundamental physical, mechanical, and chemical behaviors have not been quantified. This paper presents a Molecular Dynamics (MD) simulation performed to compare the swelling behavior of three organoclays, composed of Wyoming montmorillonite as the base clay, and modified with three alkylammonium cations: tetramethylammonium (TMA); decyltrimethylammonium (DTMA) and hexadecyltrimethylammonium (HDTMA), which were chosen to study swelling as a function of increasing cation tail length. Continuous swelling behavior of simulated clay was derived by introducing a small amount of incremental water molecules for each simulation up to a water/clay ratio of approximately 0.25. The simulation results validated the use of combined ClayFF and CVFF as the appropriate basis for simulating the structures of alkylammonium intercalated phylosillicates, and facilitated comparison of the swelling behavior of the base unmodified clay and organoclays that were modified by TMA; DTMA and HDTMA.

This paper describes the results of a laboratory testing program to assess the efficacy of a reactive core mat (RCM) for remediation of contaminated, subaqueous sediments. The 1.25 cm (0.5in) thick RCM (reactive material such as organoclay with geotextile layers on top and bottom) is placed on the sediment and 7.6 to 10.1 cm (3 to 4 in) of overlying soil is placed on the RCM for stability and protection. The RCM can provide the same physical isolation of the sediment from the overlying water and benthic organisms provided by traditional soil caps. However, in addition, the RCM overlay has the potential to: provide a remediation layer that will adsorb and/or neutralize target dissolved contaminants from the underlying sediment through diffusion and advection through the permeable RCM layer; prevent resuspension of fine contaminated sediments; and serve as a stable, protective foundation material for new, overlying sediment that can be used to promote regeneration of biota.

Sustainable redevelopment to meet increasing urban expansion has mandated the increased redevelopment of contaminated land. Current national / international environmental regulations, and increased disposal costs for landfilling, has necessitated a need for sustainable and cost efficient in situ remediation alternatives. Stabilization / Solidification (S/S) techniques offer a viable solution for the amelioration of unacceptable environmental risk, particularly effective in heavy metal remediation. However, uncertainties over long term effectiveness and durability, and previously low landfill disposal costs had limited its utilization. Effective characterization of the stabilized material and evaluation of its leaching and containment properties are required, to ensure long term effectiveness and improve design confidence. Zinc contaminated kaolin clay, stabilized with CEM II Portland Limestone cement, was tested using a suite of leaching tests designed for monolith specimens. Evaluations of leaching for zinc and selected master species (Al, Si and Ca) were undertaken, at different intervals of hydration (28, 150 and 300days). Results show that zinc is successfully contained and partitioned within the cement stabilized kaolin clay, but does not exhibit amphoteric leaching. Increased hydration time increases the stabilized materials chemical durability regardless of kaolin degradation, but does not modify pH dependent leaching trends.

Laboratory tests were conducted on foundry waste sand treated with up to 8% bagasse ash (a pozzolana) by dry weight of soil to assess its suitability for use in a waste containment application. Specimens were prepared at molding water contents - 2, 0, +2 and +4% of the optimum moisture content using British Standard light, BSL (standard Proctor) compactive effort. Index properties, hydraulic conductivity (k), volumetric shrinkage strain (VSS) and unconfined compressive strength (UCS) tests were carried out. Results obtained showed no significant change in index properties. However, hydraulic conductivity values recorded for 2 and 4% bagasse ash treatment met the regulatory 1 x 10^–9m/s requirement. Specimens treated with a minimum of 4% bagasse ash met the minimum UCS value of 200 kN/m² requirement. VSS values recorded met the regulatory requirement of less than 4% for specimens treated with a minimum 2% bagasse ash content. The overall acceptable zone for bagasse ash treated foundry sand for use in waste containment application was achieved with 4% bagasse ash content. However, the molding water range 11.2 – 12.6%. is too narrow for practical purpose. It is recommended that the activity of bentonite in foundry sand be recovered rather than addition of bagasse ash.

The study evaluated, through a series of diffusion tests, the attenuation capacity of a compacted residual clayey soil with and without the addition of Portland cement (0 to 2%), when subjected to a static load (100 to 500 kPa) simulating the action of a solid waste mass and to an acidic contaminant solution, prepared with pH varying in the range of 1 to 6, enriched with the toxic metal cadmium. The results indicated that the investigated soil might be employed as containment barriers for industrial and mining solid waste, especially with the addition of Portland cement, as it showed low hydraulic conductivity and high attenuation capacity.

Mineral barriers are extensively used in various applications to either protect the environment from hazardous substances or to simply maintain water in certain areas. Due to the nature of the application there are different requirements that the applied lining system has to meet. A higher sealing performance and a high capability to cope with the surrounding environment generally allow for a longer functional lifetime. For most applications this is a necessity to achieve the ultimate goal of a sustainable environment and thus to save natural resources as well as to protect the environment. The most commonly used mineral barriers are Compacted Clay Liners (CCL), Bentonite Enriched Soils (BES) and Geosynthetic Clay Liners (GCL) offering individual advantages and disadvantages. When used under the right circumstances all systems can achieve good results, however all sealing systems have certain limitations. New concepts have been developed to improve the properties of the different lining systems in order to enable them to better cope with any occurring detrimental effects. On Trisoplast®, as one of these modified barriers, intensive independent testing has proven that the performance of the mineral material can be significantly improved by making use of a special bentonite-polymer technique.

Using fly ash as a material for the mineral sealing layer is justified by its chemical, physical and mechanical properties. Fly ash is characterized by its ability to absorb and reduce leaks. Power-industry wastes possess the ability to retain various contaminants and heavy metals. The aim of the paper is to determine the fly ash properties as a material built into the insulating layer of storage yards. Based on the test results it can be stated that fly ash hydraulic conductivity depends on the test method and the sample preparation technique. Moisture content at compaction affects fly ash hydraulic conductivity. Compacted fly ash shear strength and resistance to failure are significantly greater than those of corresponding mineral soils in terms of graining in similar consolidation test results. Compaction effort and fly ash moisture at compaction have considerable effect on values of mechanical parameters.

An Electro-kinetic phenomenon is used not only to accelerate the consolidation process of soft clays, but very much used for decontaminating the soils and enhancing the chemical stabilization process. In this paper, an attempt is made to study the influence of Initial Moisture Content (IMC), Voltage and Spacing of electrodes on the effectiveness of electro-osmotic stabilization of soft clays. Using electro-kinetic cell, experiments were conducted for a varying voltage of 20 to 80 V, IMC of 60 to 80 % and electrode spacing of 10 to 30 cm. It is found that as the IMC and voltage increase the volume of water collected at cathode also increases at any time interval. Increase of voltage not only enhanced the process of dewatering but very much also the propagation of cracks especially at lower IMC. Decrease of the spacing of electrodes reduces the dewatering process and also early attainment of strength. The flow of current was uniform at higher IMC irrespective of voltage and spacing. It is concluded that eventhough spacing, voltage and IMC are determining the effectiveness of Electro-osmotic stabilization, the influence is in the order of IMC > Spacing > Voltage.

Low permeability cut-off walls are regularly employed for groundwater and pollution control. In Europe, they are usually built out of cement-bentonite slurries. Generally, bentonite-cement slurries are studied in the laboratory to evaluate its strength, hydraulic conductivity and chemical compatibility. In this study, a nondestructive technique is proposed as an alternative method to monitor the hardening of clay treated with cementing additives. The technique makes use of bender elements to measure the shear wave velocity and the small-strain shear modulus (G₀). Bender elements were installed in a flexible-wall hydraulic conductivity cell, so that G₀ as well as the hydraulic conductivity of a single sample could be monitored versus time. Experimental work was carried out on cemented kaolin clay using Portland cement. Monitoring of G₀ was shown to provide valuable additional information to study the stiffening of cemented clay.

Geosynthetic Clay Liners (GCLs) used in covers may be subjected to the adverse impact of desiccation coupled with cation exchange. Dense factory-prehydrated (DPH) GCLs have been introduced. Permeability tests alternated with drying phases were performed on a DPH GCL using distilled water (DW) and a 0.0125 M CaCl₂ solution. Mild and severe desiccations were simulated. The impact of dry/wet cycles on permeability was found to be limited even for severe desiccation with DW as hydrating liquid. Conversely, the hydraulic conductivity increased dramatically after a few cycles of severe desiccation using the CaCl₂ solution. Reduction of self-healing capacity caused by cation exchange appeared responsible for the increase in permeability. In case of partial desiccation, the permeability remained low for desiccation water contents higher than the prehydration water content (45%), and increased irreversibly for desiccation water contents lower than that of prehydration. Test results indicated that the permeability of DPH GCLs subjected to dry/wet cycles coupled with cation exchange strongly depends on the extent of desiccation; consequently, as conventional GCLs, DPH GCLs should be protected (e.g., by adequately thick surface layers) in covers where severe desiccation and cation exchange may occur.

As part of the plan to increase the capacity of the Port of Brisbane, reclamation of a total area of 235 ha is in progress. The main geotechnical issue at the site is the extremely soft material dredged from the Brisbane River and Moreton Bay shipping channels. Over part of the reclamation area, Menard Bachy was selected by the Port of Brisbane Corporation to carry out deep soft ground consolidation, using the method of Vacuum Consolidation. In 2007, a trial area of 1.5 ha was first implemented. Following successful completion of the trial, a second and larger project was begun in 2009. The new single cell area of 9.3 ha is currently under vacuum depressurization and the soil consolidation is expected to be complete by early 2011. A significant feature in the vacuum system adopted is the 15m deep soil-bentonite cut-off wall incorporating a high-density polyethylene (HDPE) liner, which is required at the periphery, to isolate the vacuum areas over the depth of the permeable layers in the subsurface profile. To ensure the confinement required for the depressurization, the slurry wall and incorporated liner are joined to a surface cap HDPE liner to complete an air and water tight seal around and over the block of soil. The initial trial incorporating the deep cut-off wall was a first in Australia and was a success in terms of both outcome and execution with depressurization, under the vacuum membrane, being maintained constantly in the range of –0.80/–0.70 bars over a long period of time of 18 months. Confinement work on the current project, which is taking place over a significantly larger scale and using improved technique, is currently in progress. The ability of Soil-Bentonite slurry walls incorporating HDPE liners to perform as air-tight and water-tight barriers under high pressure differential (0.8 to 0.7 bars) and subjected to significant deformation has been tested on these large scale projects. The barrier system has proven to be effective for considerable periods of time.

Capillary Barrier Cover Systems were recently designed and constructed over contaminated materials at the Rocky Mountain Arsenal (RMA) located near Denver, Colorado. The design and compliance of the infiltration control component of the covers at the site are governed by a quantitative percolation criterion . During an initial field demonstration for evaluation of alternative cover systems in achieving the criterion, formation of a capillary barrier was found to play a critical role. This paper discusses design studies, construction criteria and construction approaches that were developed for this capillary barrier cover system, as well as initial information from the long-term monitoring of the cover system performance. The use of index soil properties for the soil storage component of the cover was found to be suitable for construction specifications, but required implementation of a comprehensive borrow source characterization. The use of a laboratory column test program proved relevant to identify the different capillary barriers suitable for the full-scale cover system.

Monitoring the geomembrane's integrity becomes an essential part of recent construction quality assurance (CQA) and quality control (QC) programs in order to guarantee an optimal performance of the liner barrier. However, the existing electrical methods of leak detection for landfill barriers are generally expensive and allow only a temporary detection of geomembrane damages. Authors suggest a novel permanent electrical leak detection method for landfill barrier. Compared to existing methods, the proposed Electrical Circuits Method (ECM), which is based on the installation of big parallel electrical circuits over the landfill site, appears more cost-effective and more affordable

In an academic project in Iran University of Science and Technology, an instrumented landfill containing two separate cells is constructed for monitoring landfill behavior. About 4600 tons of MSW is disposed in three layers in each cell with a height of 5.2m and the dimensions of 35m x 57m. In one of the cells, leachate is recirculated on the landfill. By measuring the temperature, leachate, gas and settlements of landfill, landfill behavior due to the special kind of Tehran's MSW (which is high moisture content, mostly organic part) is investigated. The measured temperature in both cells shows the average temperature in cells about 45 and 47 °C and shows with presence of a moderate final cap (40cm of compacted clay) the variation of air temperature from –5 to 40 °C have just an effect on the upper layer of waste but does not change the average temperature of whole landfill very much.

The interaction between geotextiles and geomembranes in landfill applications is subject to temperature change due to seasonal variations as well as exothermic reactions occurring in the waste body and is a critical factor governing the stability of modern lining systems. An experimental research study was undertaken to investigate temperature effects on interface shear behavior between geotextiles and smooth/textured geomembranes. The physical laboratory testing program consisted of a series of direct interface shear tests under different normal stress levels at a range of test temperatures. A temperature controlled chamber (TCC) was designed and utilized to evaluate shear displacement-failure mechanisms at higher temperatures. This paper describes the development of the test system. The results of initial experimental investigations are presented to show how interface shear behavior of geotextile-geomembrane interfaces changes with temperature.

Until recently the temperature of landfill liners and its effects on the service-life of composite liners have received relatively little attention. However, there is growing evidence that the temperature may be sufficient to significantly reduce the service-life of the liner components, in particular that of the high-density polyethylene geomembrane. This paper presents a numerical study of the use of expanded polystyrene (EPS) geofoam and shredded tires as thermal insulators between primary and secondary liners. The temperature level on the secondary geomembrane is shown to be lower than the case without thermal insulation. Accordingly, the service-life is longer. The paper also highlights some of the challenges that would be associated with the potential use of geofoam or shredded tires and suggests that while using geofoam or shredded tires warrants consideration, much care would be required in the detailed design and construction of the liner.

Municipal Solid Waste (MSW) landfills may contain aluminum from residential and commercial solid waste, industrial waste, and aluminum production wastes. Some aluminum-bearing waste, particularly aluminum production wastes, may react exothermically with liquid within a landfill and cause uncontrolled temperature increases, significant changes in gas composition and pressure, nuisance odors, changes in leachate composition and quantity, consumption of the surrounding waste, and damage to engineered components. This paper discusses techniques for determining whether an exothermic aluminum waste reaction and/or combustion exists in an MSW landfill facility and provides recommendations for the safe disposal of aluminum production waste.

This study was conducted to evaluate temperature, gas, and leachate data at two landfills in similar climatic regions (Detroit, Michigan, USA and Asahikawa, Hokkaido, Japan) to determine the interrelations between heat production and resulting waste temperatures and gas and leachate levels in landfills under variable decomposition conditions. Significant temperature increases occurred under long-term anaerobic conditions. Stable elevated temperatures under anaerobic conditions were observed for wastes at central locations. Seasonal fluctuations in both temperature and gas existed at shallow depths and near perimeter locations. Placement of an overfill of fresh wastes over old wastes affected temperatures, yet did not significantly influence existing anaerobic conditions. Temperatures increased at shallow depths and decreased at greater depths to reach the characteristic waste temperature profile observed in landfills located in temperate climates. Introduction of semi-aerobic conditions using passive gas vents resulted in high temperature variations. Heating and cooling were both observed, depending on vent location with a net heating effect of 1.3 to 3.0°C over 4 years. Temperatures of wastes below a leachate mound were low and varied less in comparison to wastes above the leachate mound under semi-aerobic conditions. Waste temperatures were lower above high leachate mound than low leachate mound.

Fly ash produced by power plants in the United States occasionally contains significant amounts of unburned carbon due to the use of low nitrogen-oxide and sulphur-oxide burners in recent years. This ash cannot be reused in concrete production due to its reactivity with air entrainment admixtures and is largely placed in landfills. Roadways have high potential for large volume use of high carbon fly ash (HCFA). HCFA can be activated with lime kiln dust (a disposed residue of lime production plants) and used as the base layer for newly paved roads. However, in such applications, the leaching of heavy metals from fly ash-stabilized base layers can cause significant environmental concerns. A series of column leach tests (CLTs) were conducted to investigate the leaching potential of chromium (Cr) from the fly ash-stabilized soils. The results indicate that an increase in LKD amount, pH, and fly ash content have significant effects on leaching behavior of heavy metals from soil-fly ash mixtures. The leaching of Cr in CLTs exhibited a first flush pattern, and the concentrations quickly decreased to below EPA maximum concentration limits (MCLs) for drinking waters. In addition, a groundwater contamination modeling computer program (WiscLEACH) was used to estimate the Cr concentrations at different depths and distances from the center alignment of the center of the HCFA stabilized base layer.

For environmental impact assessment, the Japanese leaching test (JLT) is frequently used in Japan. The grains in JLT are ordinarily smaller than 2.0 mm, but the grain size might be impractical. Therefore, this study investigated the influence of controlled clod size on the leaching characteristics of represented crushable waste; drinking water sludge (DWS). First, compaction tests were conducted using DWS. Second, batch and column leaching tests were performed using various clod size fractions of DWS. The Al concentration was analyzed to investigate the effect on plant growth. Consequently, 81% of DWS was crushed to less than 2.0 mm clod size by compaction, so the clod size in JLT is reasonable for environmental impact assessment of DWS utilization. Furthermore, results of batch leaching tests using clods smaller than 0.25 mm substituted for the maximum Al concentration in column leaching tests.

Synthetic lightweight aggregates — produced by commingling coal fly ash and waste mixed plastics — represent an alternative lightweight aggregate for use in construction. Although the presence of trace contaminants in fly ash is an obstacle to its use, previous studies have shown that encapsulation of fly ash in plastic can mitigate toxin leaching. This paper presents a study on the reduction in leachable arsenic, lead, and selenium from coal fly ash incorporated into these aggregates. For the arsenic leaching study, two fly ashes were tested: a high-carbon Raw ash and low-carbon Processed ash. Aggregates were created with ash-to-plastic ratios of 0:100, 20:80, 50:50, and 80:20. The ashes and aggregates were subjected to leaching at various pHs. Arsenic levels were measured using graphite furnace atomic absorption. For the lead and selenium leaching study, Processed ash was utilized in the creation of 80:20 aggregates. Lead and selenium levels in the leachate were measured using an inductively coupled plasma spectrometer. Results demonstrated a reduction in leaching for all three compounds. The observed reductions were significant, with up to 96.69% reduction achieved for arsenic, 96.94% for selenium, and 80.58% for lead. It can be concluded that utilization of fly ash in SLAs provides a beneficial ash reuse strategy.

Recycling plastic water bottles has become one of the major challenges world wide. The present study provides an approach for the use of plastic waste as reinforcement material in soil, which can be used for ground improvement, sub-bases and subgrade preparation in road construction. The experimental results are presented in the form of stress-strain-pore water pressure response and compression paths. Based on experimental test results, it is observed that the strength of soil is improved and compressibility reduced significantly with addition of a small percentage of plastic waste to the soil. In this paper, an analytical model is proposed to evaluate the response of plastic waste mixed soil. It is noted that model captures the stress-strain and pore water pressure response of all percentages of plastic waste adequately. This improvement in strength due to inclusion of plastic waste can be advantageously used in ground improvement projects.

In situ soil stabilized with fly ash has become a practical and economical solution for soil stabilization. Understanding the pH-dependent leaching behavior and mechanisms controlling release of major and trace elements from soil-fly ash mixture is important for assessing the environmental impacts associated with using fly ash in soil stabilization. A pH-dependent leaching test was used to investigate the leaching behavior of soil-fly ash mixtures used in roadway construction. Three broad leaching behaviors as a function of pH were observed from the soils, the fly ashes and the soil-fly ash mixtures: (i) leaching of Ca, Cd, Mg, and Sr follows a cationic pattern where the concentration decreases monotonically as pH increases; (ii) leaching of Al, Fe, Cr, Cu, and Zn follow an amphoteric pattern where the concentration increases at acidic and alkaline pH; and (iii) leaching of As and Se shows both the behaviors following oxyanionic pattern where concentration increases at acidic and alkaline pH and those show anomalous leaching behavior. Consistency in leaching behavior for many elements was observed, which is believed to be due to solubility-controlled. The difference and inconsistency for As and Se are likely due to different controlling mechanism, such as sorption, or solid-solution formation.

The shear strength and stiffness of expansive soil and rubber (ESR) mixtures were evaluated systematically in this study in undrained axisymmetric compression. The materials tested included the Pierre shale residual soil from the Front Range of Colorado and granulated rubber with 6.7-mm nominal maximum particle size. The three mass-based rubber contents used were 0, 10 and 20%. All specimens subjected to element testing were consistently prepared at soil states defined for a single level of relative compaction equal to 95% and optimum water content, based on the standard Proctor compaction curves of each mixture. The effects of the rubber content and mean effective stress were systematically evaluated by performing isotropically consolidated undrained triaxial tests at mean effective stresses equal to 50, 100 and 200 kPa. Bender element tests were used to determine the small-strain stiffness of the Pierre shale residual soil and its ESR mixtures at mean effective stresses of 50, 100 and 200 kPa. The critical-state friction angle increased with increasing rubber content for specimens compacted to and tested at similar initial states. Conversely, the stiffness of the ESR mixtures decreased with increasing rubber content for all three levels of mean effective stress used in the tests. The drop in stiffness was more significant at low mean effective stresses.

The diffusion of five volatile organic compounds was quantified in a 2mm thick high density polyethylene (HDPE) geomembrane commonly used in bottom landfill liners in Europe. The VOCs under study were benzene, toluene, dichloromethane (DCM), trichloroethylene (TCE) and 1,2-dichloroethane (DCA) that were mixed together. Glass diffusion cells were especially designed for this purpose. Blank tests were performed to quantify the sorption onto the cell during diffusion testing. Tests were performed in duplicates. The partitioning coefficient of the geomembrane was also determined using batch tests that lasted approximately 100 days. Values of the partition coefficient range between 2 and 101, with the order DCA=DCM<TCE=Benzene<<Toluene. The evolution of concentration with time in the source and receptor chambers of the diffusion cells were interpreted using the numerical code Pollute. Values of diffusion coefficients obtained range between 4.8 x 10^–13 and 1.2 x 10^–12 m²/s with the order benzene<TCE<DCA<DCM. Values of partitioning coefficients and diffusion coefficients are in the range of values obtained in the literature and resulting permeation coefficients are also consistent with data from the literature.

In 2009, all Polychlorinated biphenyl (PCB) contaminated materials were excavated for permanent disposal from the Pottersburg PCB Storage Facility. The facility was comprised of four cells of PCB contaminated soil and waste constructed between 1984 and 1987. This exhumation presented a unique opportunity to evaluate the performance of the cells' barrier systems. The barrier systems of Cells 1 and 2 included a leachate collection system, leak detection system and compacted clay liner, whereas Cells 3 and 4 were comprised of a leachate collection system, leak detection system, geomembrane and compacted clay liner. Samples of the liner system were collected and depth profiles of PCB concentrations were determined through the leachate collection system, geomembrane (where present) and compacted clay liner for each of the four cells. These profiles provide insight into the contaminant migration pattern of PCBs over the 22 to 25 year storage period. This paper reports on the performance of the barrier system in Cell 3 in containing PCBs at the Pottersburg PCB Storage Facility. In addition, results from laboratory sorptive tests examining the migration of PCBs through the geomembrane samples taken from the base liner are presented. As well, the diffusion and sorptive properties of the excavated geomembranes with respect to BTEXs are presented. Pollute modeling software was used to established diffusion coefficients for BTEX with respect to geomembrane. These results were used to analyze the contaminant migration profile through the barrier system.

Polybrominated Diphenyl Ethers (PBDEs) are used as flame retardants in plastics, textiles, electrical components and other materials to slow the ignition and spread of fire. PBDEs bioaccumulate in blood, breast milk, and fat tissues and they show association with endocrine disruption, reproductive toxicity, and developmental neurotoxicity in rodent studies. The total PBDE concentration in landfill leachate is reported to be up to about 1,500 ng/L. In this study the sorption of PBDE to high-density polyethylene (HDPE) geomembrane is examined by performing sorption laboratory tests. Techniques to be used for assessing the diffusive properties including partitioning, diffusion and permeation coefficients of the geomembrane are discussed.

Results from physical experiments are reported to quantify the deformations of geomembrane wrinkles near overlaps in an underlying geosynthetic clay liner (GCL) when subjected to vertical overburden pressure. The height and width of the wrinkle decreased, but a void remained between the geomembrane and GCL when subjected to a vertical pressure of 250 kPa. It was found that the deformation of the geomembrane wrinkle was not significantly altered by the presence of the overlap and that for the conditions tested there was no discernable opening of the GCL overlap when subjected to stress. It is anticipated that the proximity and orientation of the geomembrane wrinkle relative to the GCL overlap and the stress conditions arising from the deforming wrinkle can influence the hydraulic performance of the GCL overlap.

A liner material apart from having practically lower hydraulic conductivity values should be environmentally safe. This paper apart from addressing the environmental concern associated with the use of fly ashes, also deals with their hydraulic conductivity behavior when the fly ashes are stabilized with lime alone or in combination with gypsum. The hydraulic conductivity studies were carried out in the laboratory by standard falling head test method. The addition of gypsum to lime treated fly ashes in minimizing the leaching of lime has also been investigated, and it is observed that a good correlation exists between lime leachability and hydraulic conductivity. It has been observed that the leaching of trace elements can be minimized by the addition lime along with gypsum. It is quite interesting to note that the gypsum which greatly minimizes the lime leachability also reduces the hydraulic conductivity very efficiently.

A laboratory evaluation of the characteristics of reconstituted coal ash stabilized reclaimed asphalt pavements (RAP) subjected to British Standard light, BSL (standard Proctor) compactive effort to determine the compaction characteristics and California bearing ratio (CBR) values was carried out. Test results show that the properties of RAP improved when treated with reconstituted coal ash, RA (coal fly ash, FA + coal bottom ash, BA). The particle size grading improved from 99.9% coarse aggregates and 0.1% fines for 100% RAP to 93 – 99% coarse aggregate with 1 – 7% fines for the various reconstituted coal ash-RAP mix proportions. The CBR values also improved from 13 and 9% for the unsoaked and soaked conditions respectively, for 100% RAP to 60% and 66% (soaked condition) for 10%RA(40%FA + 60%BA) + 90%RAP and 40%RA(20%FA + 80%BA) + 60%RAP mixes with corresponding unsoaked CBR values of 27 and 34%. Generally, soaked samples recorded higher CBR values than unsoaked samples. The reconstituted coal ash stabilized RAP proportion of 40%RA(20%FA + 80%BA) + 60%RAP and 10%RA(40%FA + 60%BA) + 90%RAP with CBR values of 66 and 60% (soaked for 24 hours) can be used as subbase or subgrade materials in road construction.

Nearly 4.2 billion tons of non-hazardous by-products are generated from agricultural, domestic, industrial, and mineral sources and have been used in land filling, due to nonavailability of economically attractive use options. Coal combustion produces minute particles of fly ash that cause huge environmental damage. Land filling is undesirable because it causes, not only huge financial burdens to producers of by-producers, but makes them responsible for unknown future environmental liabilities. To address this problem, concrete researchers initiated studies to see whether these by-products could be used in concrete, as a result of these studies, many by-products were found to be efficient in concrete, thus finding cost-effective solutions to waste disposal problems. In this study an extensive experimental program was carried out to study the concrete properties with and without pozzolanic material such as fly ash, silica fume, and slag for three types of concrete mixtures. In this paper, permeability is considered as the main measuring parameter for producing durable concrete. As a result, it was found that producing durable concrete with low diffusivity and permeability without the addition of pozzolanic material is impossible.

Compacted clayey soils are used as hydraulic barriers in waste containment facilities such as liners and covers, in order to control infiltration into the waste and hence leachate from the waste to the ground water. Laboratory studies on compacted tropical clay treated with up to 16% Rice Husk Ash (RHA), was carried out using standard Proctor compactive effort; at water contents between 2% dry and 4% wet of optimum to access the suitability of the material as a land fill cover. Compacted samples, extruded from the compaction mould were allowed to air dry in the laboratory for a 30 day period to access the effect of desiccation shrinkage. Results show that changes in mass and volumetric shrinkage strain were large within the first five days of drying. Volumetric shrinkage strain increased with higher moulding water contents/water contents relative to optimum, higher RHA treatment. All specimens prepared at 2% dry of optimum and at optimum moisture content for up to 8% RHA treatment met the regulatory maximum allowable volumetric shrinkage strain value of 4%, showing the suitability of the material as a cover in municipal waste containment facility and beneficial reuse of the agro waste product.

This study focused on the consolidation characteristics of two soils stabilized with class C fly ash (CFA), lime and plastic waste. Three groups of specimens were prepared: the first group consisted of specimens prepared with 10% class C fly ash and 6% lime and then cured for 28 days; the second set of specimens was prepared with recycled plastic waste with a plastic to soil ratio (PSR) of one; and the last group consisted of specimens prepared with raw soils and compacted at near optimum moisture content and maximum dry unit weight. The last group was considered a baseline to assess the effect of CFA, lime and plastic waste on the consolidation characteristics. Results showed that CFA, lime and plastic waste stabilization reduced the compressibility of soil. In addition, both the compression index (C_c) and swelling index (C_s) decreased due to CFA, lime and plastic waste stabilization. The percentage changes in C_c and C_s varied with the type of stabilizing agents.

Fly ash is produced from the combustion of coal at power plants. Fly ash is fine-grained, well-rounded, cohesionless, and possesses a specific gravity of around 2.2. Fly ash is often placed hydraulically in fills in a loose, nearly saturated state. Therefore, it is highly susceptible to liquefaction, and it is very important to accurately estimate its dynamic properties when assessing the behavior of fly ash fills under dynamic loading. Herein, laboratory measurements of the dynamic properties of class F fly ash were performed on reconstituted specimens using the free-free resonant column method. These results indicate that the shear wave velocity of fly ash is typically around 110–150 m/s, and increases with increasing confining stress. Material damping of fly ash typically ranges from 2–5%. These results can be used to estimate the dynamic properties of fly ash for performing site response analyses on fly ash deposits.

Over the past decade, most of the reservoirs in Taiwan have been experiencing serious siltation problems. Therefore, the removal of reservoir siltation (RS) and the resource recovery of dredged material have become critical issues for national security and economical development. Controlled low strength material (CLSM) mixed with non-standard recycled material can be used as an excellent alternative for backfill construction. This research conducts an experimental study to explore the possibility of using RS in CLSM for backfill applications. Test results showed that RS can be used for producing of acceptable CLSM through proper mix design procedures. Considering the requirements of backfill applications, this study recommends a water/solid ratio of 0.8∼0.9 and a cement/water ratio of 0.4∼0.5 can be used for the design. The results show a promising solution to reuse reservoir siltation, save natural resource of granular fill, and ensure the quality of backfill constructions in most cases.

Stability analysis for MSW landfills is based on limit equilibrium methods of general use in Geotechnics, in spite of the fact that rheological behavior of MSW is different from that of typical soils: stress-strain curves show an increase of strength without the occurrence of failure within the normal range of strain levels of shear strength tests, and shear strength and deformability parameters alter along time. Furthermore, there is the additional problem of the representativeness of waste samples for laboratory tests. This paper proposes to evaluate strength parameters of MSW by means of in-situ static load plate tests carried out in a sanitary landfill in the metropolitan region of Sao Paulo, Brazil, and Terzaghi's formulation for ultimate bearing capacity of direct shallow foundations. Cohesion-friction angle curves for different strain levels obtained by analysis of in-situ tests are presented and discussed.

In this study, calcium carbide residue is used as a binder to treat over-wetted clays being used as embankment filling material in China highway engineering practice. To prepare the treated soil specimen, calcium carbide residue is added in the sampled soil with contents of 4%, 6%, and 8% (dry soil weight basis). For comparison, lime is also used as the binder to treat soils with contents of 4% and 6% (dry soil weight basis). To investigate the performance of treated over-wetted soils, unconfined compression strength (UCS) test, water soaking durability test, and California Bearing Ratio (CBR) test are carried out. The factors controlling the aforementioned mechanical properties of treated soils are discussed. From the tests, it is found that calcium carbide residue treated soils have better performance than that of lime treated soils. It is concluded that calcium carbide residue can be adopted as an alternative binder to treat over-wetted soils being used as highway embankment filling materials.

Dredged sediment poses a particularly difficult challenge for disposal throughout the world. At the Savannah Harbor alone (Savannah, GA, USA), over 6 million cubic yards of sediments, are dredged annually and are currently being stored within disposal sites adjacent to the harbor, confined by 42 miles of dikes. High maintenances costs associated with the disposal of these sediments, along with proposed land use changes in the area, have become primary drivers for identifying productive reuse applications for this dredge material. Given the composition of the sediment, it has been investigated as a suitable component for the raw materials in brick manufacture. This paper summarizes research conducted to assess the viability of producing fired bricks from Savannah harbor dredge. Results from physical and chemical characterization of the dredged materials demonstrate that they are suitable components for brick manufacture. Brick production, including bench scale extrusion and firing, have been performed in a controlled laboratory setting. Results indicate that the bricks, produced from dredged sediment blended with minimal additional materials, indeed comply with standard strength and absorption requirements.

The importance of minimizing detrimental impacts of erosion on construction sites has been considered a pressing issue for decades. Conventional erosion control near wetlands utilizes hay bales and silt fences. Although these conventional methods may reduce the amount of erosion, their effectiveness is infrequently reliable. Recently, compost berms and compost filled geo-fabric tubes have been used as a means of erosion and sedimentation control. Compost used for this purpose comes primarily from agricultural (non-animal) and landscape waste. Up to now, most of the research on compost as an erosion and sedimentation prevention material has been on the observed efficacy of the methodology. The research presented in this paper investigates two engineering aspects of compost. The first aspect is the material properties of the compost using standardized geotechnical test methods. These tests include specific gravity, grain size distribution, hydraulic conductivity, direct shear tests, and triaxial tests. The second aspect is the geoenvironmental influence that the compost has on the water passing through. The laboratory test program consisted of passing synthetic rain water through compost samples and measuring the chemical and pathogenic content in the effluent. The compost used for erosion and sedimentation control is typically wood waste, and landscape/vegetative waste composts. For the material properties tests, three different composts, which are used by landscape contractors, were tested. For the geoenvironmental tests, forty different samples from locations throughout Massachusetts were used. Tests included of nutrient, chemical, biological, suspended solids and pH analyses. Test results indicated negligible impact of effluent on protected wetlands as compared with the traditional use of silt fences and hay bales.

This paper discusses the effect of two co-products from lignocellulosic biorefineries on a typical Iowa subgrade soil in terms of laboratory measured strength and compaction properties. Emphasis is given to detailed data analysis of laboratory test results in comparing treated soils with untreated soils under different moisture conditions and additive concentrations. Results reveal that the bio-energy co-product (BCP) additives investigated in this study are promising materials to improve strength property of the typical Iowa soil classified to CL or A-6(8) for geotechnical applications. Especially, the co-product A containing higher lignin content is a more effective additive to reduce plastic property and optimum moisture content of soil.

A bioreactor landfill was constructed by the city of Calgary, Canada to sustainably manage solid waste. It includes initial operation of bioreactor landfill under anaerobic conditions to recover biogas, then under aerobic condition to convert waste into compost and finally mining compost for reuse. The bioreactor landfill is equipped with leachate recirculation systems to accelerate the decomposition of organic waste. Rapid decomposition leads to large quantities of landfill gas, which in turn results in rapid settlement. The landfill gas produced is collected and used for energy recovery. The methane present in landfill gas is a potent greenhouse gas and the use of landfill gas in energy recovery reduces the environmental impact of this gas. The gas extraction and leachate recirculation systems are quite expensive. Hence the bioreactor landfill requires efficient operation to maximize gas generation while having excessive settlement. This manuscript presents details of a full scale landfill bioreactor performance during the anaerobic phase of the sustainable landfill, including leachate generation and recirculation, and gas generation and monitoring of performance date including temperature and settlement.

This paper presents a study that investigates the geopolymerization of red mud, a major industrial waste from alumina refining, and fly ash, also an industrial waste from coal combustion, using very limited non-waste materials. Different synthesis parameters (e.g., red mud to fly ash ratio, sodium silicate solution to solid mixture (red mud and fly ash) ratio, and different types of sodium silicate solution) were varied to assess their influences on the mechanical properties of final geopolymer products. The results of unconfined compression testing show that these factors have significant influence on the mechanical properties of the synthesized geopolymers. Depending on the synthesis conditions, the unconfined compressive strength ranges from 3 to 13MPa, and the high values are comparable with certain types of Portland cement. The process of geopolymerization was confirmed by the composition of the final products analyzed by X-ray diffraction. The findings suggest that the two major industrial wastes, red mud and fly ash, can be reused to produce geopolymers that may replace Portland cement and hence be applied in civil infrastructure construction.

In Hudson County, New Jersey, there are more than two million tons of leftover chromite ore processing residues (COPR). Part of COPR was used as construction fill materials spreading the problem to a larger area. High solubility of some chromate compounds along with their toxicity is threatening the environment as well as the human health. The primary objective of this manuscript is to demonstrate an efficient and optimum way to recover chromium and iron from COPR in the production of chrome steel or stainless steel. In this research, COPR was thermally treated to recover iron together with chromium. The research applied techniques used in steel manufacturing to extract metallic iron and chromium from COPR. An extensive experimental program was performed using a Thermo-Gravimetric Analyzer (TGA) to thermally treat chromium contaminated soils with additives at different temperatures and under different reducing environments. The optimum chemical composition of soil and additives to be used in the melts was evaluated based upon the thermodynamic properties of the mixture to ensure good phase separation, least amounts of iron and chromium oxides in the slag and minimum variability of final product (steel or iron with chromium). The impact of other oxides on the steel making process was evaluated to minimize the adverse impact on the process. The research demonstrated the feasibility of the proposed process.

This study focused on the manufacture, hydraulic and mechanical properties of a porous plastic-based cementitious (P-PBC) material. P-PBC, produced from plastic waste, soil and aggregates, will offer an effective technique for reducing stormwater runoff, improving water quality and providing a structural pavement suitable for pedestrian and vehicular loadings. It will also help divert a large amount of plastic from landfills and incinerators thus playing a crucial role in the recycling efforts currently underway. P-PBC specimens with different plastic to soil/aggregate ratios were prepared and then tested for hydraulic conductivity (k) and indirect tensile strength (ITS). Results showed that k and ITS values of specimens were within the expected values found in the literature for porous pavements. It was also found that the k values decreased with the increase of percentage of plastic waste. ITS, on the other hand, increased with the amount of plastic waste. The study findings indicated that P-PBC could be an effective Stormwater Best Management Practice with significant positive economic and ecological implications.

Geopolymer concrete was synthesized from coal fly ash, which contains the range of silica and alumina that is needed for the formation of geopolymer phase. Studies on the leachability of geopolymer concrete made from fly ash have shown that it leaches out elements such as arsenic (As), chromium (Cr) and selenium (Se), which are of great environmental concern due to their toxicity and high mobility in the alkaline pH range that can be found in pore solution of geopolymer concrete. The leaching of these elements in high pH environment can be reduced by the addition of calcium that aids in the formation of calcium silicate hydrates (CSH) or precipitates of calcium. In this study, recycled concrete aggregate (RCA) was used as the additional calcium source in making geopolymer concretes. Different mixes were produced with 100% natural aggregate (coarse and fine) and by replacing 10% and 50% coarse aggregate with coarse RCA. The Dutch availability test (EA NEN 7371) was utilized in investigating leachability from the geopolymer samples. The results demonstrate that the use of RCA affects the compressive strength and reduces the leachability of oxyanion elements from geopolymer concrete.

Construction and demolition materials such as recycled crushed rock and recycled glass account for a major proportion of the waste materials present in landfills in Australia. Using recycled glass and crushed rock in road pavement applications would significantly reduce the need for quarry-based virgin materials. Furthermore, recycled materials could be used in parts of the country where aggregate sources are scarce. This paper discusses the suitability and applicability of recycled glass when used in blends with crushed rock for road pavement applications. Performance of the blends was measured using an extensive suite of geotechnical engineering laboratory tests including basic classification tests along with modified compaction, California Bearing Ratio and Los Angeles abrasion tests. Repeated load triaxial tests were also conducted on blends. The test results indicated that the recycled glass could be blended with recycled crushed rock by up to 30% by mass and provide satisfactory engineering performance to be used as a pavement subbase material.

To increase the recycling potential of mixed glass, this research proposes to manufacture segmental retaining wall (SRW) brick, made from recycled unsorted mixed glass bonded with plastic. To demonstrate the proof of concept different percentages of mixed glass is mixed with heated plastic to produce a new material that could be used as segmental retaining wall (SRW) bricks. For optimum glass plastic mixture compressive strength of the final product exceed the ASTM requirement for that of segmental retaining wall (SRW) bricks. Due to the outdoor landscaping application, the aesthetic qualities of these bricks will be investigated so that colored bricks can be manufactured using the optimum glass plastic mixture. The durability of bricks made of optimum glass plastic mixture compared well with that for current SRW bricks in commercial use. The life cycle cost analysis suggested that the cost of manufacturing glass plastic bricks is much cheaper than the segmental retaining wall (SRW) bricks. Hence the outcome of this study is the production of a viable, superior and inexpensive SRW brick made from recyclable materials that is sent to landfills.

In the west bank, the stone cutting industry consumes large amounts of fresh water and produces even larger amounts of viscous liquid waste known as "Stone Slurry Waste". Calcium Carbonate (CaCO3) is the main constituent of slurry waste in addition to other minerals from parent rock. Stone slurry waste is usually disposed in open areas in the west bank. This practice causes serious environmental problems. Every year death of humans and animals are reported due to drowning in open slurry waste ponds. Moreover, disposal of slurry waste in agricultural land causes a reduction of water infiltration, soil fertility and plant growth. This paper presents the engineering properties of stone slurry waste and documents successful attempts to utilize the stone powder from slurry waste in the production of different construction materials. In this study, waste water from stone slurry was used in concrete production and the resulting properties were compared with the concrete produced with tap water. The results showed that the waste water of stone slurry can be used successfully in concrete production.

This article presents a study of the valorization of polluted rivers sediments after treatment by stabilization. The paper is divided into three parts. The first part presents the process of treatment, which was selected to stabilize organic and inorganic pollutants present in sediments. The second part deals with the experimental campaign and methodology adopted in this study. The third part is devoted to the study and analysis of the main results of valorization of treated sediments included in the composition of a self-compacting material intended for backfill trenches. Several formulations with different ratio of sediments, sand, cement and lime were investigated. The keys parameters determined were the immediate bearing capacity ratio and the compressive strength at 28 days. 75% of treated sediments, 25% of sand, 2% of cement and 4% of lime constitutes the formulation, which was selected.

This paper proposed a method to use stabilized mucky clay as backfill material in highway embankment projects. Sand is added into the mucky clay in the proposed method with the purposes of increasing the permeability of mucky clay, reducing the initial water content, and improving its mechanical properties. Then, lime powder is added into the mixture of the mucky clay and sand to improve engineering properties of the treated mucky clay to fit the requirement of the projects. Behaviors of the treated mucky clay are also tested and analyzed using a series of lab test. Test results demonstrated that the stabilized mucky clay using the proposed method is adequate for backfill material in embankment projects.

The yield stress and viscosity of bentonite suspensions treated with Sodium Pyrophosphate (SPP) were measured to investigate the applicability of modified bentonite suspensions as a permeation grout. The yield stress and viscosity were significantly reduced with the addition of Sodium Pyrophosphate (SPP). The main advantage of using SPP is the temporary nature of the reduction in yield stress and viscosity; both parameters increase with time and exceed the values of the original suspension without the SPP. Permeability tests were conducted to verify the effectiveness of the bentonite suspensions in decreasing the hydraulic conductivity of the sand. Permeated samples were prepared with clean sand and bentonite using 7.5, 10, and 12% bentonite suspensions. The results showed that hydraulic conductivities of the sand decreased by 4, 4.5 and 5 orders of magnitude with grout bentonite contents of 7.5%, 10% and 12%, respectively. These findings suggest the possible application of Sodium Pyrophosphate (SPP) treated bentonite suspensions in permeation grouting for controlling hydraulic conductivity.

A series of steady-state vertical infiltration tests were conducted on a 1.0 m high soil column of Clayey Sand over Fine Sand under various boundary conditions. The test results show that the pore-water pressures in the Clayey Sand were always negative due to the existence of the underlying Fine Sand. The pore-water pressures in the Clayey Sand increased with the increase in flux or head at the upper boundary and the rise of the water table at the lower boundary, but the infiltration rate generally decreased following the rise of the lower water table. The unsaturated hydraulic conductivity values of the Clayey Sand were found to be closer to the predicted drying conductivity curve rather than to the wetting conductivity curve. The Clayey Sand was found to be unsaturated even when the measured pore-water pressures were either zero or positive suggesting possible air entrapment in the soil during the downward movement of water.

Moisture distribution in a bioreactor landfill depends on various parameters such as the leachate recirculation system and its geometric configuration, hydraulic properties of municipal solid waste (MSW), and others. Hydraulic properties of MSW are the most important parameters that govern leachate distribution. Studies on the effect of saturated hydraulic properties of MSW on moisture distribution are documented in literature; however, studies on the effect of unsaturated hydraulic properties are scarce. The main objective of this paper is to model the effect of unsaturated hydraulic properties of MSW on leachate distribution. Since MSW is unsaturated, flow of two immiscible fluids (leachate and landfill gas) is expected; therefore, a mathematical model that accounts for a two-phase system is implemented which considers leachate as wetting fluid and landfill gas as non-wetting fluid. This model is validated based on reported laboratory test results and mathematical modeling studies. The effect of unsaturated hydraulic properties of MSW indicates significant variations in leachate distribution under steady state and gravity drainage conditions, which shows that its consideration is essential in the design of leachate recirculation systems in bioreactor landfills.

The proper engineering of landfill bioreactors require operation in a manner that maximizes waste decomposition and gas generation while making use of the settlement that occurs. Settlement in landfills consists of interacting multiphase media with each phase exhibiting variations both in time and space. There are mathematical models available to evaluate the processes of biodegradation, gas generation and transport and distribution of moisture within a landfill. At the same time, many existing waste settlement models focus on compression of waste solids but overlook the contribution from other phases. An effective model for landfill settlement should be able to consider settlement, gas generation and fluid transport simultaneously. However, the phase interactions involved in landfill settlement are not well understood. Apart from the theoretical uncertainties in the phase interactions, a major obstacle to developing a multiphase settlement model is the amount of data required to calibrate and validate the model. This manuscript presents data from study of a full scale waste cell currently operated as a landfill bioreactor. The waste cell is equipped with gas collection and leachate recirculation systems, and is instrumented to collect time resolved data. This waste cell is being used as a research facility to study the impact of leachate recirculation on gas production and settlement.

The proportion of the constituent materials in fresh MSW varies from location to location; as does the attendant shear strength. Highly heterogeneous nature of MSW composition makes it difficult to compare shear strength properties of samples from two different locations. The wide variation in shear strength properties is attributed to the heterogeneous nature of the composition and the level of biodegradation of MSW. MSW shear strength found in literature typically indicates an increase in the angle of friction of with degradation. However, it is not very clear what contributes to the cohesive properties in MSW. Cohesion values from the published studies are often difficult to interpret and compare due to the limited information on the composition of the tested materials. The research described in this paper is an attempt to understand how the shear strength properties vary with the rapidly biodegradable organic fraction in MSW. During this research a series of laboratory tests were conducted on unsaturated synthetic MSW using an automated direct shear testing machine. The preliminary results from this investigation revealed that the increase in the fraction of organics (such as food waste) can result in decreased friction and increased cohesive properties in MSW.

Municipal solid waste (MSW) dumping sites have attracted much attention recently due to the increasing demand for land brought on by urban construction in China. In this study, a three-month field experiment on the effects of combining air injection and leachate recirculation was analyzed based on the indicators examined, such as solid waste moisture content (MC), volatile solid (VS), and dissolved total organic carbon (DTOC) of the leaching solution, as well as chemical oxygen demand (COD), biochemical oxygen demand (BOD), and NH₄-N of the leachate. Results show that 58.9% of VS and 97.5% of DTOC were reduced during the experimental period. The pH level of the leachate was always basic (pH > 7.4), indicating that volatile fat acids (VFAs) did not accumulate. COD content of the leachate remained at a low concentration range of 1200–1500 mg/L. The BOD/COD ratio of the leachate was low and the biodegradability of leachate worsened. The VS/FS ranged from 0.16–0.21. The quick decrease in release intensity of pollutants in the leachate illustrated the acceleration of stabilization of the dumped MSW through the combination of forced aeration and leachate recirculation.

Constitutive models developed for describing the water retention curve (WRC) and unsaturated hydraulic conductivity (K_θ) of soil are parameterized for MSW. Samples of shredded (maximum particle size = 25 mm) MSW were compacted to three dry densities for WRC and K_θ measurement. The water retention curves were measured using the hanging column method. The unsaturated hydraulic conductivities were measured using the multistep outflow method utilizing transient outflow data from the hanging column tests. The measured WRC and unsaturated hydraulic conductivity were used to fit two commonly used constitutive WRC and K_θ models developed for unsaturated soils. The constitutive models were parameterized using non-linear regression to the equilibrium WRC and measured K_θ data. The constitutive models for the WRC and K_θ are capable of reproducing measured WRC and K_θ data when properly parameterized. Root mean squared error water contents (θ_RMSE) ranging from 1–2% were calculated between the measured and modeled WRCs. Unsaturated hydraulic conductivities calculated using the constitutive models were generally within one order of magnitude of the measured K_θ. Parameter estimation for the K_θ functions requires inclusion of K_θ data in the parameter estimation method.

There have been several exposed geomembrane cover (EGC) applications permitted as long-term interim cover systems for landfills since 1992. The first EGC as final closure was approved by State of Georgia in 2009. This EGC utilizes a 1.5-mm (60-mil) reinforced polypropylene geomembrane adhered with flexible photovoltaic (PV) cells to generate electricity. This paper presents a simplified design approach used to improve previous EGC designs by incorporating a modified anchor trench configuration to more effectively address wind uplift and ease the installation process. Calculations for the anchor trench pullout due to the modified anchor trench configuration are discussed and the wind suction coefficients, previously published using models tested in wind tunnels, are modified by considering suction forces generated under the EGC and other similar designs that have taken place over the last thirty years. The paper concludes with a case study of a final EGC design which incorporates PV cells to generate revenue during the post closure period. The case study demonstrates the design simplifications, determination of wind uplift forces, design considerations for anchor trench pullout and anchor trench dimensions.

This case history discusses the geosynthetic construction, use, failure, and repair of the 1995 Evaporation Pond at the EnergySolutions Clive Facility. A high priority is placed upon management of water that has contacted waste and that is stored in the Pond. A geosynthetic investigation into the root cause of repeated excessive leaking in the Pond is discussed. Two failure mechanisms were discovered and are discussed: damage due to maintenance activity and poor patch extrusion welding technique. The poor patch extrusion welding consisted of a large number of sharp, upwardly turned hardened extrudate that appeared to have worn against an overlying HDPE liner and created raised bumps and tears in the overlying liner. It appears that the combination of this unsatisfactory geosynthetic lining welding technique coupled with Pond operation and maintenance created a preventable geomembrane failure mechanism. Successful subsequent repairs of the 1995 Evaporation Pond are discussed.

This paper provides an alternative design and construction methodology for an exposed geomembrane cover at risk of uplift by wind. The alternative anchorage can be used with both exposed geomembrane covers and exposed geomembrane covers hosting flexible laminated photovoltaic (PV) solar panels. The exposed geomembrane cover can be designed using earth anchors consisting of corrosion resistant materials in lieu of the traditional soil-filled anchor trenches and/or anchor benches (trench/bench) to secure the exposed geomembrane against wind action. Penetrations made by the earth anchor alternative can be covered by flexible solar panels adhered onto a carrier geomembrane. The earth anchor penetrations are covered by the carrier geomembrane and solar panels, thereby creating a uniform hydraulic barrier and sustainable cover system. It is anticipated that this alternative anchorage method may reduce many of the issues that arise from constructing on-slope anchor trenches (e.g., constructability, drainage from benches, and exposure and handling of the existing buried waste).

Land erosion is an increasing problem that is seriously affecting our country in recent years. During the period October-March on certain low areas of the country there is massive flooding, and on the hills and certain mountainous territories there is a large amount of land and surface erosion. The erosion phenomenon is larger near habitated zones, where the amount of damage is greater and occurs over large areas. One of the areas in our country affected by this phenomenon is the District of Lezha, which has become a periodic flooding zone due to its geographical position. The main purpose of this study is to define the distribution of the erosion rating relative to the covered area based on, vegetation, chute tilt and precipitation indices. This study should provide information and guidance on land usage to farmers, communities and state regulatory officials, pertinent to agrarian properties and woodland surfaces.

A vertical probe (VP) employing a water jet has been developed for assessing scour potential and erosion rates of sediments typically found at the bottom of rivers or streams. The probe for "In situ Evaluation of Scour Potential (ISEP)" is based on the idea that analysis of the probe penetration rate into the soil correlates with scour rate and erosion potential. The method discussed herein aims at measuring the potential scour rate in situ and as a function of depth. Scour rates determined with this method at shallow depths are found in agreement with values published for similar sands. Results presented herein show high erosion rates in the near surface for all velocities tested (water velocities varying between 0.5 m/s to 5.8 m/s). As the probe moved deeper into the soil, the erosion rate dropped rapidly for all water velocities tested. These results, being consistent with previously published results, support the utility of this technique for quickly assessing scour hazards.

Erosion threatens coastal infrastructure and natural habitats throughout the United States. Conventional soil amendments, such as lime and Portland cement, are effective for improving soil strength and resistance to erosion, but exopolymers have the potential to improve sediment stability without the environmental risks of caustic or toxic compounds. This paper describes how the erosional resistance of a pure kaolinite clay is enhanced using two exopolymer analogues, guar gum, a neutral polysaccharide, and xanthan gum, an anionic polysaccharide. A cohesive strength meter (CSM) is used to measure the critical value of shear stress τ_oCr of high water content muds, representative of newly placed hydraulically pumped fill. Guar gum produces a nine fold increase in τ_oCr, while void ratio increases of 9% result in approximately 25% decreases in τ_oCr. Xanthan gum provides much less improvement than guar gum in cation free mixtures because of electrostatic repulsion, but sodium and calcium cations in the pore fluid negate this effect. Practical applications of exopolymers for erosion control are discussed.

We present a computer simulation of hydraulic erosion on levees, dams, and earth embankments, with emphasis on rill and gully initiation and propagation. We focus on erosion features that occur after an earthen structure is overtopped. We have developed a 3D fluid and hydraulic erosion simulation engine using Smoothed Particle Hydrodynamics (SPH). We present the results of digital simulations for different soil types. Furthermore, small-scale physical models of levees composed of different soils were constructed and tested experimentally. The digital simulations are compared to physical experimental results to validate the computer models.

There are approximately sixty thousand bridges throughout the US identified with unknown foundations, which results in serious problems for evaluating the bridges' current state of risk, particularly due to scour. This paper presents results of a soft-computing model to determine the depth of unknown bridge foundations based on the use of Artificial Neural Networks (ANN) trained on data collected from foundation design and inspection records. This approach allows for correlating between the depth of foundation and a series of parameters associated with the bearing capacity and foundation design of bridges. A case study is presented based on a pilot project considering existing bridges from the TX-DOT Bryan District. Some of the conditioning parameters considered for the ANN training includes structure, material type of bridges, soil properties, type and amount of loading, among others. A supervised learning algorithm is applied to train multilayer neural network models using information from bridges where full records were available.

The threat of terrorist attack on subway system using explosives intensifies considerably in recent years. Explosion inside subway tunnels may damage the subway structures and result in further socioeconomic losses. Specifically, the century-old single-track cast-iron subway tunnels in New York City and London are very vulnerable to this type of attack. In this study, a 3D Finite Element procedure was developed to investigate the damage of cast-iron tunnels in saturated soils subject to internal explosions using medium amount of explosive (75 kg TNT) that might be perpetrated by terrorists. The stress path and damage mode of these tunnels subject to internal blast loading were firstly investigated, based on which the damage of cast-iron tunnel lining was simulated using hardening elasto-plastic model considering shear damage. The study then focused on the influences of soil-structure interaction and the compression of saturated soil under large compressive loading. It was found in the study that compressibility of saturated soil influenced significantly the damage of cast-iron lining while the effect of soil-structure interface was much smaller.

Explosions on the ground surface develop shock waves that travel through the subsurface and can cause significant damage to underground structures, such as tunnels. Factors, such as amount of explosives, distance from the source to the structure, and nature of the intervening medium determine the magnitude of stresses induced at the structure. This paper presents results of centrifuge model tests and numerical model analyses where the effects of surface blasts on underground tunnels were studied. Both centrifuge modeling and numerical analyses offer different means of modeling the behavior of soil and underground structures under dynamic, very large strain loading, such as explosions. The results of centrifuge model tests, in the form of measured strains on underground tunnels, are presented. Numerical modeling was used to investigate the effects of specific variables, such as mass of explosives and thickness of soil cover.

Nesbitt Dam is a composite earth-fill embankment with stone masonry core wall, non-overflow and spillway section. Historical survey data indicate that the downstream hillside and right abutment has been subjected to movement over a 60 year period from 1920 to 1980s. Inclinometers established during a 2007 subsurface investigation depicted 12.7 millimeters (0.5 inches) of movement within a lacustrine silt stratum at a depth of approximately 30 meters (100 feet) six months after installation. This paper presents the procedures and analyses used by Gannett Fleming to identify, model, and design a remedial solution to limit future hillside instability. This paper focuses on the extensive laboratory testing program conducted on the lacustrine silt and adjacent strata to thoroughly establish the engineering properties of site soils.

Deterministic seismic hazard assessment of a 16 km long road sector was done using GIS tools. The analysis was done by calculating the factor of safety against sliding for each 2 m x 2 m cylinder of soil using the slope stability analysis equations for the translational failure that were modified for horizontal ground motion. The results of this study show that hazard prone area increases exponentially with an increase in ground acceleration.

In this study, a probabilistic method is proposed for estimating soil property and model uncertainty of a rainfall infiltration model in unsaturated soils using field observation of pore-water pressures. The proposed method is formulated based on the Bayesian framework and solved using the Markov Chain Monte Carlo simulation method. A case study of a field test of rainfall-induced slope failure is presented to illustrate the proposed method. It is found that all the parameters except q₂ are well identified within a small region. The posterior distributions of k_s and α show a normal shape and two parameters are positively correlated. Before the rain period, the 95% total prediction uncertainty bounds indicate a relatively good model performance. During the rain period, the results are less accurate.

Cyclic liquefaction behaviour of sand with fines at four fines contents under non-symmetrical (about the axis of zero deviator stress) cyclic load was examined. Three forms of cyclic liquefaction behaviour were indentified, namely, cyclic instability, cyclic mobility, and transition behaviour. Experimental evidence showed that the occurrence of these three forms of cyclic liquefaction behaviour can be predicted by the equivalent granular state parameter prior to undrained shearing. Further, the triggering of cyclic instability (with or without stress reversal) can be predicted with the instability curve obtained from monotonic undrained tests.

As the impacts of failing geotechnical infrastructure become more apparent, Structural Health Monitoring (SHM) is now more commonly being applied to geotechnical assets: levees, earth dams, landslides, and foundation soils. In particular, real-time monitoring programs are now becoming considered essential for monitoring the performance, or identifying impending failure, of high-risk geosystems. This paper presents several case studies of real-time monitoring of embankments and slopes on Minnesota Department of Transportation (Mn/DOT) projects using MEMS-based in-place inclinometer, ShapeAccelArray (SAA), systems. Background on the SAA inclinometer-accelerometer array system is presented as well as observed project and performance benefits with respect to other displacement monitoring systems. Benefits of real-time monitoring and the larger concept of performance monitoring and SHM of geotechnical assets by remote sensing are discussed.

The strength of levees can be affected during fluctuations in the water table. It is also possible for the climate to have an influence on the position of the water table in an earth levee. Traditional methods have resulted in approximate methods for dealing with the transient fluctuations of the water table in a levee. These approximations are generally accepted in engineering practice but the question can be rightfully raised as to how these approximations compare to a rigorous transient combined seepage and slope stability analysis. Software technology has significantly changed in recent years and is now at the point where it is much easier to perform transient seepage analyses. There are new questions that can be asked. Does an effective stress analysis diverge significantly from the 3-stage Duncan (1990) analysis? If so, under what conditions? This paper compares the Duncan (1990) three-stage methodology for analyzing rapid drawdown scenarios to a combined transient seepage and slope stability analysis. Traditional limit equilibrium methods will be utilized in the slope stability analysis and the accommodation of saturated and unsaturated pore-water pressures will be considered. Analyses of a number of typical cross-sections will be considered in order to determine the potential influence of geometry. The intent of the paper is to illustrate scenarios under which the Duncan (loc. cit.) methodology produces similar results to the results of a more rigorous analysis.

Sinkhole activity is a covered loss under Florida's current regulatory statutes regarding property insurance, and several thousand subsidence investigations are completed annually for homeowners with cracking distress and other possible indicators of sinkhole activity. The majority of these insurance claims are located in Florida's gulf coast communities, north of and including Tampa. Here, the limestone is shallow and is overlain by sedimentary and wind-blown sand and clay layers. In addition, there is often, but not always, a vertical downward gradient from the surficial aquifer to Floridan aquifer. In Florida's geologic past, before the sand and clay layers were laid down, changes in the ocean level caused weathering of the limestone surface, creating an uneven surface where subsequent infills of loose sands and soft clays have still not consolidated. This has created subsurface conditions that appear to be sinkholes, but are not. Sinkhole formation is chiefly the result of raveling of overlying granular soils into voids, cavities and caves within the limestone. Proper analysis of these cases requires the geotechnical engineer to understand the regional geology, and the geologist to understand the engineering conditions under which damage can occur to a structure. The case studies presented allow the reader to distinguish the subtleties between general subsidence and subsidence due to true sinkhole activities.

Generally, the compaction of the aquitards was recognized as the main component of land subsidence caused by groundwater withdrawal. However, based on the observation of land subsidence in Su (Zhou)-(Wu) Xi-Chang (Zhou) area, the deformation in aquifers is comparable with the deformation in aquitards. Under the situation of the significant compaction in pumped aquifers, the permeability change in the pumped aquifer has to be considered which can significantly affect the water head change calculation. In this study, the numerical method is used to analyze the sensitivity of the parameters (i.e., the relative compressibility of aquifers and aquitards; the permeability in pumped aquifers) influencing the development of the subsidence which may be useful to create land subsidence model incorporating this kind of new finding mentioned above. First, a baseline case model is created to evaluate the effectiveness of the presented numerical model; and subsequently, the parametric study is conducted to analyze the relative importance of the calculated parameters in land subsidence; finally, some discussions and conclusions can be obtained based on the calculation results.

In this study, a physical model test was conducted to investigate the relative settlement of the aquifers and the aquitards during the pumping test. The soil layers in the physical model were simulated from practical (SU-XI-CAHNG) pumping strata. The dimensions of the cubical model tank were 0.6m in length, 0.5m in width and 1.0m in height. The model soils consisted of four layers with two aquifers and two aquitards alternating placed. The pumped aquifer was located at the bottom of the tank, and the thickness of each layer varied. The hydraulic head and the deformation of each soil stratum were monitored during pumping test by small diameters pore pressure tubes and settlement telltales. Throughout the pumping test, the compression of the pumped aquifer at bottom consisted of 50% of the overall observed settlement measured at surface of soil (land subsidence). The time effect of the sandy aquifer deformation was also observed. A bilinear relationship between the land subsidence and the decrease of the hydraulic was verified in this experiment. It is confirmed that, although the recharge had a significant effect on the land subsidence potential reduction, the subsided ground would not rebound due to the recharge. The model test improved the understanding of the land subsidence due to groundwater withdrawal.

Many investigators have proposed a number of models to describe the land subsidence mechanism. However, some difficulties still exist, for example, the influence of the pumped layers' deformation on its hydraulic characteristics, the creep behavior in the pumped aquifers, and the coupling of the consolidation and the seepage. Therefore, a consolidation-seepage-creep coupling model is proposed in this study; a one-dimensional formula of the coupling model is derived including methods of determining these model parameters. The creep tests are implemented on both clayey aquitard and sandy aquifer layers simulating the Changzhou region to obtain the critical parameters of their creep behavior. Finally, results from both the current model and an elastro-plastic model are compared with the field observation data. It is concluded that the proposed model is a better approach to simulate the land subsidence in Changzhou.

This paper presents the case history of a culvert failure and the results of finite element modeling and evaluation of the failure mechanism. The 1.8 m by 1.8 m reinforced concrete box culvert runs parallel to and at a distance of 0.6 meters from a 18.9 m high mechanically stabilized earth (MSE) wall, and a concrete flume located above the culvert discharges storm water into the culvert through concrete drop-inlet structures. When the wall approached its final height, the culvert experienced extensive cracking, and it had to be braced internally to prevent total collapse. Results of the finite element modeling indicate that, as the MSE wall settled, it induced significant drag on the culvert due to its virtually rigid connection with the wall through the flume and the drop-inlet structures. The resulting bending moment in the culvert exceeded its moment capacity, causing cracking and failure of the culvert.

This paper reviews a class of slow-moving landslides that is prevalent in most of the deep-seated leeward valleys of East Oahu. Attention is placed on one slide in particular that shares similarities with the others in terms of morphology, topographic setting, rainfall patterns, subsurface soils and groundwater conditions. Discussion centers on geotechnical properties, correlations to rainfall patterns, slope monitoring results, slope stability modeling, and potential stabilization measures. It is found that most comprehensive solutions are impractical, except perhaps for the construction of a toe buttress. Light residential use may still be possible in the absence of comprehensive stabilization if risks are understood and prudent design features are adhered to. This is conceivable only because of the slow-moving character of the sliding processes, which generally does not pose a threat to health or safety.

Prevention of landslide has always been important to have smooth flow of traffic along highways. Various methods of slope stability analysis are used to evaluate the degree of stability of landslide mass before and after the prevention work. Although each method is supposed to be appropriate for a specific situation, prevention plan designed with any method should give same level of stability to the prevented landslide. However, it is observed that factor of safety of a slope calculated with different slope stability analysis methods differs. This paper deals with a case study of a landslide prevention work along a highway sector and its reevaluation using different methods of analysis for possible ground motion due to earthquake.

Heavy rainfall can lead to shallow slips on slopes which are often initially in a state of partial water saturation. A multiphysics approach and advanced constitutive modeling are necessary to take into account the physical key processes in partially saturated soils during rainfall events, such as water flow through the solid matrix, soil water retention behavior and the effects of matric suction on the mechanical behavior. The elasto-plastic constitutive model ACMEG-s that includes an elasto-plastic water retention model with wetting-drying hysteresis is used in the framework of finite element modeling for the assessment of destabilizing, transient processes in a steep slope during rain infiltration. It is shown that at the onset of failure, wetting pore collapse and plastic shear strains occur in the lower part of the slope and develop upwards towards the slope surface to delimit a probable failure mechanism.

Slow movements of natural slopes are quite frequent in mountainous or hilly areas. They may display occasional crises, mostly related to the increase of pore water pressures induced by exceptional climatic conditions. A methodology consisting of combining the hydrogeological analysis and the geomechanical analysis is presented for the analysis of these phenomena. The evolution in space and time of pore water pressures obtained from hydrogeological modelling is used as input data for finite elements geomechanical modelling, in order to calculate stress variations and displacements. The proposed framework is applied to analyze a natural slope with three strategic infrastructure assets located at its toe. After being calibrated and validated, the model is applied to improve the understanding of the physical processes involved and to predict the landslide behaviour under different possible scenarios.

Landslides, primarily occurring in deep-seated landslide areas, frequently damage important roads in Nepal and contribute to massive economic losses and public suffering every year. Efforts to understand these landslides, which are often only regarded as geological phenomena, through material shear behaviour however remain insignificantly reported. In order to narrow this research gap, this paper first addresses spatial distribution of these landslides in about 150-km arterial road corridors in central Nepal, and then discusses their occurrence mechanism in terms of a relation between material shear strength and mineralogical composition. The deep-seated landslide inventory prepared out of the aerial photos and topo-sheets revealed that the landslide distribution is dominant in phyllitic and slate zones of geology while the laboratory tests on clay materials, sampled from 15 locations in the study area, in ring shear machine and x-ray diffractometer exhibited that the landslide soils, especially from the phyllitic area, possess comparatively high angle of shear resistance in a range of 20–30 degrees with remarkable influence of mica and chlorite composition, whose increased relative amount was found to result in notable decrease of the angle of shear resistance.

Ballistic soil nails have been used in the United States to repair shallow roadway landslides for nearly 20 years. The U.S. Forest Service/Federal Highway Administration "Application Guide for Launched Soil Nails" is the principal design manual for designing with ballistic soil nails and employs a simplified sliding wedge analysis using limit equilibrium concepts to determine the factor of safety of a slope reinforced with soil nails. The design methodology quantifies the tensile and shear resistance provided by the individual nails, but is limited to linear failure surfaces in homogenous materials. The paper explains some of the recent advancements in launched soil nail design methodology and provides a conceptual methodology for translating sliding wedge analysis input parameters into standard PC-based limit equilibrium slope stability programs. An improved method of estimating bond strength is presented. The shear contribution of ballistic soil nails, often ignored in conventional soil nail design, is shown to be an important contribution to the stability of ballistic soil nail landslide repairs.

Defining the limits and monitoring the movements of an active landslide are essential in the design, construction, and performance evaluation of a stabilization remedy. Landslide limits are often defined by an understanding of the subsurface stratigraphy and interpretation of field data. Landslide mass movements can be influenced by precipitation, local ground water fluctuations, or construction activities. The use of instrumentation to monitor and interpret movements during rehabilitation construction activities can provide: (i) an early warning of future potentially catastrophic movements; and (ii) the opportunity to optimize planned stabilization construction activities should unexpected movements occur. In this technical paper, the instrumentation monitoring system is described for an active landslide in western Pennsylvania where the stabilization plan was designed based on the location of the failure surface and measured movements. The instrumentation system used for assessing the failure was maintained and supplemented during construction. Data obtained from this instrumentation system will be presented, the use of the data to develop the stabilization plan will be demonstrated, and modification of the stabilization plan will be discussed. At the time of this paper, stabilization activities are ongoing; further refinement to the design may occur.

Traditional in-place inclinometers are widely used for displacement monitoring of slopes and other geo-structures. But these inclinometers have limitations such as (a) numerous cables requirement, (b) sensitivity to electromagnetic interference, (c) narrow measuring range. The new optical fiber sensor based in-place inclinometer can overcome the above limitations. This paper introduces a new type of in-place inclinometer based on fiber Bragg grating (FBG) sensing technique. A series of FBG sensors are glued onto the surface of a plastic rod for measuring bending strains and axial strains. Based on the beam theory, these strain results are used to calculate the displacement and rotation angle of the rod tip. A series of rods with FBG sensors can be connected together and installed into a geotechnical structure for displacement monitoring. Several calibration tests have been conducted in laboratory and the calibration results are in good agreement with theoretical results. The new FBG-based in-place inclinometers have been applied in a subway tunnel in Shenzhen, China, and a slope site in Sichuan, China. This technology will be used to monitor a retaining wall in Hong Kong.

Wireless Sensor Networks (WSN) can be useful in subsurface geo-event monitoring. Hazard monitoring and effective in-situ characterization are some key issues that can be addressed by use of WSN in the subsurface. In this study a new concept of WSN application for subsurface geo-event monitoring was investigated. The new concept of functional signal takes advantage of the variations of signal strength of radios transmitted between the distributed sensor nodes of a WSN to monitor and characterize the sensed area. Experiments demonstrated that calibrated wireless signal strength variations can be used as indicators to sense changes in the subsurface. Based on the experimental results the new approach can be exploited further to provide a sensing methodology to identify and monitor subsurface hazards through the evolution of select physical conditions in the subsurface. These subsurface hazards can range from intrusion of a chemical plume to the onset of a slide which could change markedly the physical properties of the host soil, hence the functional signal transmitted with an embedded WSN.

Presented herein is a summary of the results from the first two years of a four-year study on damage detection and health monitoring of buried, segmental concrete pipes, such as those used in urban water distribution networks. The rapid assessment of damage to such networks from earthquake-induced permanent ground deformations is an essential component to recovery efforts. To identify the failure modes that occur in the pipelines subjected to permanent ground deformation and to assess the performance of sensor technologies for detecting these modes and for potential use in situ, large-scale tests were performed at the NEES Lifeline Experimental and Testing Facility at Cornell University. The predominant failure modes identified in the tests performed to date include compression at all joints and combined compression and bending at the pipe joints closest to the fault. Accurate measurements of the pipeline displacements and strains were recorded up to the compressive and flexural failure of the pipeline joints.

A four-story reinforced concrete building retaining earth on one side and exhibiting large lateral displacement and structural distress was instrumented and monitored for over four years. The rectangular building measuring 52.42 m by 71.32 m is open to the elements and thus subjected to large temperature variation. The application of classical lateral earth pressure theories and analysis methods for back analysis were unsuccessful in predicting the observed behavior of the building. The instrumentation program involved the installation of eight vibrating-wire displacement transducers measuring the building movements in the longitudinal and transverse directions, and 12 electrolytic tiltmeters mounted on the building wall abutting the retained soil backfill to measure the wall rotation. The instruments were equipped with temperature sensors and were connected to an automatic data acquisition system accessible via a remote connection. The monitoring results revealed the presence of a complex soil-structure interaction involving the effects of temperature on the volumetric strains of the building and their effects on the building movements and the development of lateral pressures in the retained earth mass. The results of the monitoring program are presented in this paper.

Currently, the use of advanced sensing technologies is rapidly increasing in research and practice, but the implementation of sensors and health monitoring of earth structures in the undergraduate curriculum has not kept pace with advances in the state of practice. This paper introduces the development of educational modules based upon the installation of a remotely-monitored sensor network. The modules will expose students in geotechnical engineering to advanced sensor technologies and opportunities to observe and analyze data that are collected in real time. Initial assessments indicate that introduction of even basic concepts on sensors increases student comprehension and confidence on the subject.

This paper reports on an ongoing research program to develop a capability to: (1) measure cyclic and permanent displacements of field sites, and (2) characterize and estimate the three-dimensional in situ dynamic properties (at low and large strains) of sites for strata ranging from ground surface to a depth of about 30 m. A number of shape-acceleration arrays (SSA) have been installed at the NEES Wildlife Refuge area to monitor the site low-strain response as well as earthquake induced liquefaction, permanent deformation and lateral spreading. This array provides accurate dense measurements of permanent three-dimensional displacements along with three-dimensional accelerations. The installed array recorded moderate site accelerations during the M_L=7.2 Baja California earthquake of April 04, 2010. This paper presents: (1) preliminary one-dimensional analyses of the recorded Wildlife Refuge site response during this earthquake, and (2) an overview of a new multidimensional data reduction and identification technique for a systematic advanced site characterization.

Soil liquefaction during earthquakes causes major destruction. Liquefaction occurs when pore pressures increase to the point where the soil effective stress is very low, reducing soil strength to the point where existing loads cannot be supported. Reducing susceptibility to liquefaction has traditionally been done by grouting, drains or densification. A new method of reducing liquefaction susceptibility is presented: immobilizing pore water. A gel-like chemical is added to saturated soil. The resulting material is not conventional soil", and does not liquefy in the conventional sense. Excess pore pressures are still generated, but effective stress is not reduced according to the classical equation. The result is that the soil retains a considerable amount of strength. This paper gives preliminary results of cyclic triaxial tests on clean Ottawa density sand impregnated with gel. A procedure for preparing very loose triaxial specimens by freezing is reviewed. The results indicate liquefaction susceptibility is significantly reduced.

This paper presents a site-specific seismic analysis for a multi-high rise project in West Jakarta, Indonesia, where subsurface soils mostly consist of stiff clay and alluvial deposits up to 260 m deep. The latest seismic ground motion prediction equations were employed to develop design ground motions using a probabilistic seismic hazard analysis (PSHA) approach. Selection of appropriate design earthquake acceleration time histories and treating the variations of subsurface soils using all available soil data were pivotal to developing the most reliable site response analyses using combination of equivalent linear (SHAKE) and fully non-linear (D-MOD) programs. The design elastic response spectrum was generated not only based upon the results of site response alone, but also using the latest empirical (seismological) approaches, where the actual site amplification of recorded motions from worldwide data on similar soil conditions was considered.

In this paper, comparison of the results of strain controlled and stress controlled cyclic hollow torsional tests, using energy approach, on sand-silt mixtures is presented to shed light on the influence of fines on cyclic resistance of soils. The results indicated that the limiting fines content was not dependent on the method of loading and was a physical characteristic of tested soil. The definition of intergranular and interfine relative densities could describe the result obtained in this study. In addition, the results showed that the frequency of loading had no effect on dissipated energy up to initial liquefaction for sand-silt mixtures with various fines content less than FC_lim, both in strain and stress controlled tests.

Liquefaction during earthquakes induces such damage of existing structures as uplift or settlement, depending on the weight of structure. It is important to mitigating damage occurring by liquefaction to take some countermeasures against harmful vertical displacement. This study specifically focuses on countermeasures against settlement induced by liquefaction of existing structures with sheet pile walls during earthquakes. For this purpose, the study considers the effects of sheet pile walls on decreasing liquefaction-induced settlement of existing structures using the model tests under normal gravity (1 g) conditions that simulate the situation of existing structures founded on sand deposits. Results show in the following: (1) The longer the sheet pile walls that are installed, the more markedly settlement of structures can be reduced. (2) Combined adaptation of sheet pile walls installation with a decrease in groundwater level engenders a great degree of reduction in the settlement of structures than with adaptation of the single technique of the sheet pile wall installation or dewatering of GWL.

Damages of ground anchors during any devastating earthquake are well known. Researches on the topic of ground anchors under both static and seismic loadings are important for geotechnical engineers. Geotechnical applications of horizontal strip anchors are well known for structures subjected to uplift loading like towers, pipelines, high rise building foundations etc. In this paper, an analytical method to compute the vertical uplift capacity of horizontal strip anchors under both static and seismic conditions are described. The pseudo-static approach is used with the limit equilibrium method to obtain the net seismic vertical uplift capacity factor for unit weight component (F_γd) for horizontal strip anchor by considering the distribution of soil reaction on the simplest planer failure surface through the use of Kötter's equation. Results for F_γd are computed for various combinations of input parameters like soil friction angle, embedment ratio, both horizontal and vertical pseudo-static seismic acceleration coefficients. It is observed that with increase in both the seismic acceleration coefficients, the uplift capacity factor decreases significantly. However, the uplift capacity of horizontal strip anchors increases with increase in embedment ratio, as expected, in seismic conditions also. Present results are compared and found in good agreement with the results available in literature.

The Mashhad power plant is located in the eastern north of Iran in a region of high seismicity. A seismic hazard analysis was performed based on the most recent seismo-tectonic data to determine the design ground motion parameters. These parameters estimated four different design levels. The ground motion parameters for the Maximum Design Level (MDL), Design Basis Level (DBL) and Construction Level (CL) were obtained from a probabilistic seismic hazard analysis (PSHA) whereas the MCL was derived from a deterministic analysis (DSHA). The PSHA followed the conventional pattern consisting of the following elements: (i) identification of the seismic sources within a certain radius from the site, (ii) definition of the seismicity through a recurrence relationship for each source using the Kijko-Sellevoll approach, (iii) selection of suitable attenuation relationships, and (iv) generating curves showing the probability of exceeding different levels of ground motion at the site during a specified period of time. For the DSHA, the characteristics of faults within the area of interest was assessed based on topographic, geologic and aeromagnetic maps, air photos, field investigation, and a comprehensive search in the literature. Results are presented in terms of peak ground acceleration (PGA) and acceleration response spectra.

This paper presents a case history involving the seismic evaluation of the Patillas earth dam constructed in 1914 in southeast Puerto Rico. The dam is located in a region of high seismicity and like many old structures there was little or no information regarding the properties and compaction levels of the different materials used for the construction of this dam. This paper presents a description of the procedure used to estimate the material properties for the seismic analyses of Patillas Dam, with emphasis on the maximum shear modulus (G_max). The paper presents a comparison of the predominant vibration period of the dam in the transverse direction estimated using three different equivalent linear models for the dynamic finite element analyses and the values obtained from ambient vibration measurements using accelerometers placed at the crest of the dam. The resulting predominant periods for the finite element models (T = 0.42, 0.49 and 0.56 s) had very good agreement with the field tests (T = 0.43 to 0.45 s). The proposed methodology of using ambient vibration testing to help calibrate dynamic models of poorly characterized old dams proves to be promising.

This paper presents the results of a numerical investigation on the effect of rainfall on the performance of a reinforced earth wall. A series of limit-equilibrium based slope stability analyses within the framework of unsaturated shear strength, coupled with transient infiltration analyses considering actual rainfall record were performed to quantify the effect of rainfall on the performance of the reinforced earth wall in terms of factor of safety. A parametric study was additionally conducted on the rainfall intensity. The results indicated that the reinforced wall stability, in terms of factor of safety, could be significantly decreased when subject to rainfall due to decrease in shear strength of backfill casued by the reduction in matric suction. Also shown is that there appears to exist a critical rainfall volume beyond which no further significant decrease in the factor of safety occurs. Practical implications on the findings of this study will also be discussed.

In many cases, the intrusion of water (either through rainfall or capillary rise) into the subgrade or aggregate base course in road sections can result in the swelling of the subgrade, decreasing the effective stress and, consequently, the shear strength. To mitigate these adverse conditions, a geotextile drain (GD) can be introduced to intercept upward and downward water flow and divert it towards edge drains, with flow induced under unsaturated conditions. Design of this type of system for the general case of partial saturation, however, is significantly complicated by the significant scale differences in the spatial extent and hydraulic properties of the soil and geotextile layers. In this paper, a road section consisting of aggregate base course (ABC) and subgrade is modeled using the finite element program SIGMA/W. Results show that the suction head in the subgrade and the air entry value of the GD have important effects on downward water flow into the subgrade. Low air entry value geotextiles cause a decrease in suction above the GD leading to a decrease in shear strength and increase in deformation. Guidelines are presented for the efficient design of GD as capillary barriers in roadways to minimize intrusion of water into the subgrade and ABC.

This paper presents results from a study of the impact of environmental interaction on the deformation behavior of flexible pavements with geosynthetic basal reinforcement. Falling Weight Deflectometer, Spectral Analysis of Surface Waves, static plate load, and cyclic plate load tests were performed on a low-volume, geosynthetic-reinforced, asphalt pavement frontage road in Eastern Arkansas at different times of the year. The results from these tests indicate a noticeable seasonal effect in the deformation response of the pavement. The seasonal effects on the deformation behavior were assessed using simulations of heat and water flow through the pavement soils under atmospheric boundary conditions with VADOSE/W. Evaluation of the predicted suction and temperature profiles indicates that temperature affects the measured deformation response. Although the results from these tests clearly indicate that pavement sections with greater base course thickness have a stiffer response, geosynthetic basal reinforcement was not observed to lead to a substantial improvement in pavement deformation response at this site.

Concrete is a well-accepted structural material, used throughout the world. Large concentrated societies, along with their needs for sewage reticulation systems, waste water treatment plants, establishment of large factories and the frequent use of aggressive chemicals, etc., have created conditions which threatened its performance. Modern demands imposed on concrete structures create a need for corrosion protection systems in various applications. HDPE liners with integrally formed anchors for attachment to concrete are available to create a protective skin to concrete structures. The use of this type of concrete protection is growing rapidly around the world. These liners are generically named CPLs (Concrete Protection Liners or Corrosion Protection Liners). The paper deals with a clear description of CPLs, the basics of anchor design and performance, motivation for their use, typical applications, installation and jointing, testing and industry standards. It serves to open up a constructive discussion on additional uses for geo-synthetics, dealing with existing structures under threat, opportunities in the pre-cast concrete industry, major projects around the world (especially the DTSS — Deep Tunnel Sewer System in Singapore) and ways to ensure that industry standards keep pace with product developments.

As many developed countries struggle to keep up with population growth and land-development demands while improving their standards of living, deteriorating sewerage systems are becoming a problem that can no longer be hidden. Although the expansion and upgrading of existing systems is progressing, asset owners have come to realise that it is necessary to minimise their assets' lifecycle costs and to maximise their overall longevity, and have rapidly been adopting corrosion protection liners (CPLs) as a solution for both new sewer structures and the upgrading and restoration of existing ones. CPLs provide crucial protective benefits and may be utilised to maximise asset life and consequently maximise investment returns for most sewerage structures that are potentially susceptible to sulphuric acid damage. Such CPL materials as high-density polyethylene (HDPE) sheet have recently been economically incorporated into the construction of reinforced concrete structures, and it has become clear that similar methods may be employed for remediation works, providing an asset life of more than 100 years. This paper details the requirements for the successful use of HDPE CPLs on concrete rehabilitation works involving existing structures. It will analyse methods for preparing the concrete and applying the CPLs using advance grouting techniques.

Sewer systems in general undergo severe corrosion due to sulphuric acid attack which causes a serious threat to the structural integrity of the system in addition to large amount of maintenance and repair cost. Several methods and materials, such as single and double CPLs, various concrete mixes, fibre glass reinforced linings, special mortars and coatings, geosynthetic linings such as HDPE and PVC, etc are used to protect concrete from sulphuric acid attack in a sewerage environment. Typical concrete lined sewer tunnels need to function as both as ground support and Corrosion Protection Lining (CPL) systems. The CPL must be robust enough to withstand corrosion with time and thus preserve the ground support system. A CPL may be integral with the ground support system or installed separately. A composite CPL system which comprises a cast-in-situ concrete liner and HDPE or PVC lining is discussed in this paper. Attention will be given to geosynthetic HDPE CPL with respect to the technical requirements for the handling, installation and long term performance. A case history based on the Singapore Deep Tunnel Sewerage System (DTSS) project also presented.

In many developed countries, population density in the cities is increasing where urban renewal is preferred to the urban spread of previous decades. Existing trunk sewer systems in these urban areas are often undersized to cope with the increased flows and authorities are faced with the construction of new gravity sewer lines. Reinforced concrete pipes are the most cost effective means of building these pipelines in the diameter range of DN900 to DN2400. Cast-in corrosion protection liners (CPLs) offer an effective means of preventing internal corrosion of these concrete structures and assuring a 100 year service life in aggressive sewer environments. Australia has a long history in thermoplastic cast-in liners in concrete pipes and plasticised PVC has been installed into spun concrete pipes since the 1960's. More recently, high Density Polyethylene (HDPE) linings have become the preferred lining material. This paper investigates successful design and use of HDPE CPL in lining of reinforced concrete pipes and structures. The paper looks at lining material selection, material thickness, knob shape and spacing, sheet sizes and configuration. Lining materials and production processes will be compared. Joint welding using purpose built machines is another key aspect as well as testing requirements, both in the factory and for joint welding on site. Embedment of the knobs in the concrete and the integrity of welds at joints are two key quality issues. Comparisons of cost and performance are made between CPL reinforced concrete pipe and spray applied linings in pipes and with other inert pipe material types. The paper demonstrates that CPL's are an effective corrosion protection method in reinforced concrete pipes and that the inherent strength and robustness of a rigid concrete pipe combined with the assured quality of a CPL can provide a sound solution that overcomes construction and service life issues.

Landfill and mining applications often involve composite liner systems consisting of a geomembrane underlain by a geosynthetic clay liner (GCL). Because of the low shear strength of hydrated bentonite, GCLs are manufactured using needlepunching, where nonwoven fibers from one geotextile are punched through the bentonite and the opposite geotextile, to provide internal reinforcement. The industry uses an index test, GCL peel strength (ASTM D6496), to assess the quality and strength of the needlepunched bond. Although design engineers commonly specify higher peel strengths for projects with stringent shear strength requirements, the published information on this subject presents conflicting results. To address this data gap, a correlation study between peel and internal shear strength was performed, involving 40 shear strength tests on hydrated GCL samples with varying peel strengths. To limit variability, one type of needlepunch-reinforced GCL was tested, with all shear samples subjected to the same hydration and consolidation. The test results indicate that, for a given set of testing conditions, a GCL's peak internal shear strength is a function of its peel strength. The results of this study will be useful to design engineers in understanding appropriate GCL peel strength values for site-specific conditions.

Bentonite clay is widely used in Geosynthetic Clay Liners (GCLs), because of its elevated sealing capacity in presence of water. However, exposure to high concentrated inorganic solutions can change the clay fabric increasing its hydraulic conductivity. To improve the hydraulic performance of GCLs, a chemical-resistant clay (HYPER clay) was developed through treatment of a natural bentonite with an anionic polymer, Sodium Carboxymethyl Cellulose (Na-CMC). The swelling ability, water adsorption capacity and hydraulic conductivity of the HYPER clay were evaluated. Test results showed the beneficial effect of the anionic-polymer treatment on the swelling, water adsorption and hydraulic performance of the clay.

A conventional Geosynthetic Clay Liner (C-GCL) and a dense prehydrated (DPH) GCL were permeated with an acidic solution (pH=2) containing relatively high concentrations (0.025 M) of Pb, Zn, and Cu as nitrate salts. Both GCLs were permeated with distilled water prior to exposure to the metal solution. The DPH-GCL preserved hydraulic conductivity about one order of magnitude lower than the C-GCL. Breakthrough of metals occurred within three months of permeation for the C-GCL whereas it was not complete after more than one year of permeation for the DPH- GCL material. Cation exchange and precipitation of metals were the likely retention mechanisms.

We attempt to characterize with geophysical methods the state of landfill covers to detect damages that can induce preferential water pathways and unusual increase of leachate within the waste mass. The geophysical methods used were the Electrical Resistivity Tomography (ERT), cartography with an Automatic Resistivity Profiling (ARP©), and the Self Potential method (SP). We worked on experimental parcels reproducing common defaults on landfill covers (clay material and geocomposite) and on a larger scale on a french landfill cover. The joint use of these methods gives us the opportunity to test their ability to detect defects. Results on the parcels have shown a good detection of the larger cracks (0.10 m) on the compacted clay cover but a less easy detection of defaults on the geocomposite. Results on the landfill have shown conductive zones correlated with important SP variations that could indicate a preferential infiltration zone in the cover.

The containment function of geosynthetic clay liners (GCLs) used for geoenvironmental applications can be enhanced if the GCLs exhibit semipermeable membrane behavior, or the ability of the GCL to restrict the migration of solutes (contaminants). In this regard, the potential for membrane behavior in traditional GCLs that rely upon the bentonite in the GCL as the primary hydraulic resisting component has been shown to be significant. This paper provides a summary of the results of research illustrating the significance of membrane behavior in GCLs, including the factors affecting the existence and magnitude of membrane behavior in GCLs. The presentation concludes with a discussion of the relevance of membrane behavior in GCLs for geoenvironmental containment applications.

The main objective of the present study is to examine the behavior of model soil barriers of landfill covers at the onset of differential settlements with and without geofiber reinforcement in a geotechnical centrifuge. A motor-based differential settlement simulator was used for inducing continuous differential settlements to the moist-compacted model soil barrier of 25 mm thickness without any overburden during flight at 40 gravities. Polyester fibers having 90 mm length and a dosage of 0.5% dry weight of soil barrier material were used as discrete and random reinforcement inclusions. The performance of soil barriers with and without geofiber reinforcement was monitored by measuring water breakthrough and in restraining cracking at the onset of differential settlements. It was found that a discrete and randomly distributed geofiber reinforced soil barrier without any overburden was found to be marginally superior in restraining cracking and sustained large distortion level at the onset of water breakthrough than un-reinforced soil barriers.

Two-dimensional (2-D) non-linear time-domain analyses of the tensile forces and strains induced in the geosynthetic liner system of a solid waste landfill by seismic loading were conducted using a model that allows for relative displacement (slip) at the interfaces of the liner system. The analyses suggest that tensile strains and forces induced in the liner system by seismic loading will be within allowable values if the difference in interface friction angle between the top and bottom of the liner is relatively small. While the deformation at the crest of the side slope from the non-linear analyses were similar to the deformations calculated in a conventional 1-D decoupled analysis, the deformations at the toe of a canyon-type landfill calculated in the 2-D non-linear analysis was significantly greater than calculated in the 1-D decoupled analysis. The analyses reported herein were for two simplified landfill geometries and only employed one earthquake time history and one set of interface strengths. Additional analyses are required to determine if these results are representative of landfill response or are an artifact of the landfill geometry, interface strengths, and time history used in these analyses.

The purpose of this paper is to measure hydraulic conductivities of a geotextile polymer coated GCL, permeated with water, with three different permeameters: constant-flow, fixed-wall single-ring (FWSR); flexible-wall (FW), and constant head, fixed wall double-ring (FWDR). All results, except for the samples tested with the FWSR were lower than 1.0 x 10^–11 m/s, with some scatter in the test results at the relatively low bulk GCL void ratios tested. The results for sample diameters of 58 to 70 mm varied from 3.1 x 10^–12 m/s to 9.2 x 10^–12 m/s for samples tested at similar e_B values using the FWSR and FW permeameters. Although only one test was performed with a 150 mm diameter sample using the FW permeameter method, this test was found to provide the lowest hydraulic conductivity of the GCL tested (1.9 x 10^–12 m/s). This would seem to suggest the presence of some level of sidewall leakage during testing. However, diffusion testing and compatibility testing performed on this same GCL (not reported herein) suggests predominant flow through the GCL. Attempts to identify sidewall leakage using dyes were not successful.

Bentonite was modified at the nanoscale so that low hydraulic conductivity would be maintained under adverse conditions. Nanoscale modification consisted of polymerizing acrylic acid within a bentonite slurry to form a stable interconnected structure. This modified material is referred to as a bentonite-polymer nanocomposite (BPN). The BPN was then air dried and ground to simulate the granule-size distribution of granular bentonite in geosynthetic clay liners (GCLs). Index property tests indicate that BPN has different behavior than natural sodium bentonite (Na-bentonite). For example, free swell tests with natural Na-bentonite swelled to approximately 30 mL in deionized water, whereas BPN swelled to more than 70 mL in the same solution. GCLs were assembled and directly permeated with a range of calcium chloride (CaCl₂) solutions known to cause large increases in the hydraulic conductivity (k) of natural Na-bentonite. Low hydraulic conductivities (k < 3 x 10^–10 cm/s) were maintained by BPN for all solutions tested. In contrast, natural Na-bentonite tested under the same conditions had k more than 4 orders of magnitude higher (k > 2 x 10^–5 cm/s). Additional study of the properties and the underlying mechanisms of BPN are ongoing.

A series of large-scale dynamic direct shear tests were performed to measure the interface shear strength between a textured geomembrane (GMX) and a needle-punched geosynthetic clay liner (NP GCL) under cyclic loading. The study was conducted for large ranges of shearing normal stress (σ_n,s= 13 to 2071 kPa) and cyclic displacement amplitude (Δ_a = 2 to 30 mm). The experimental data indicate that the failure mode of a GMX/NP GCL specimen depends on both σ_n,s and Δ_a. All tests conducted at low to moderate normal stress levels (σ_n,s ≤ 692 kPa) produced interface failures. Partial to complete internal failures were observed for some tests at low Δ_a and high σ_n,s. Interface failures still occurred for the largest displacement amplitude (Δ_a = 30 mm) at all normal stress levels. In general, the testing program has indicated a more complex interrelationship among failure mode, normal stress level and shear displacement rate than has been previously considered for these materials.

Geosynthetic clay liners (GCLs) are important components of hydraulic barriers in waste containment systems, but leachate from the mining industry can alter their hydraulic performance. Usually increases in saturated hydraulic conductivity result, but sometimes decreases occur; the latter believed to be associated with pore-filling reactions. We report here the results of a scanning electron microscopy (SEM) study to determine whether pore-filling reactions occurred in GCLs permeated with solutions of 1.3 mM CsCl (GCLA) or 1M NaOH +1.3 mM CsCl (GCLB). SEM images reveal that in GCLA hydration induced swelling in resulted in an open fabric but ∼5 μ thick, dense and low porosity interfaces of smectite particles having a highly orientated pore structure was observed between clay domains. X-ray mapping conducted across a compression join (and into the domains on either side) indicated that Cs was largely concentrated near the compression zones, indicating that advective transport of CsCl may be along preferential flow paths between domains. Where compression joins existed in GCLB, individual domains were <30 μm in extent and direct evidence of precipitation of pore-filling phases was observed. Analysis indicates that average pore diameters were reduced by up to 30 times and flow path tortuosity would increase significantly.

The aim of this paper is to assess the validity of the geosynthetic clay liner (GCL) gas permeability coefficient obtained by the conventional testing approach for predicting gas leakage rate of GM/GCL composite liner due to a defect in the geomembrane. As a GCL is a composite-layered material, its permeability is a function of the permeability of its components (i.e bentonite and geotextiles) and flow direction. In order to investigate GCL's flow pattern under leakage condition, numerical experiments were conducted where for sake of simplicity the interface zone between the GM and the GCL has been ignored. The results show the inadequacy of using the GCL's gas permeability coefficient, obtained by the conventional testing approach, alone to predict the leakage rate. Instead, this value should be used along with the permeability coefficient of the GCL's geotextile layer to accurately describe the flow through GCL under leakage condition.

The inclusion of ethylene vinyl alcohol (EVOH) copolymer by coextrusion into geosynthetic liners would greatly reduce diffusive migration of volatile organic compounds (VOC's). The primary function of a geosynthetic liner system in a geoenvironmental application is containment of liquids and vapor that should not migrate into the surrounding environment. Existing monolithic geomembranes comprised of polypropylene, polyethylene and polyvinylchloride are excellent hydraulic and heavy metal barriers, but are not good barriers to volatile organic compounds that pose a threat to soil, water and air quality. In a composite with polyethylene or polypropylene, EVOH would dramatically improve the capability of geosynthetics to control the diffusion of gases, hydrocarbons and solvents in applications ranging from waste landfills, secondary containment, radon and vapor intrusion barriers and brown field remediation. A comparison of the properties and performance of model geosynthetics incorporating EVOH showed that EVOH improves VOC barrier properties by several orders of magnitude without substantially affecting key form and functionality of existing geomembranes.

Current research being done at EPI with PVC Geomembrane demonstrates the physical characteristics of PVC Geomembrane material outperforms normal design criteria. This paper will show that PVC Geomembrane seams can acclimate to 200% elongation without an issue in the integrity of the seam. PVC Geomembrane can accommodate 200% movement without failure. If the landfill or containment project can't accommodate 200% movement without catastrophic failure, why are we trying to make FTB seams in PVC Geomembrane that don't reach failure until +400% elongation? Film tearing bond(FTB) has been preached by the geomembrane industry as the minimum standard criteria for years. FTB is required of HDPE materials requiring the seam to be stronger than the material itself, while the material has functional elongation less than 20%. This simply isn't the case with PVC because of its high elongation, ability to conform and adjust to minor soil movement. PVC Geomembrane material with a normal strength seam of about 10 lbs per inch width can withstand 200% elongation without seam failure. Requiring the welding process to create FTB in the seam at the expense of raw material properties sacrifices the ultimate goal of geomembrane integrity. A wide sampling of seams in 0.75mm and 1.0mm PVC Geomembrane have been elongated and held at 100% and 200% elongation in a custom built apparatus for over a year. No failures in any of the variety of seams have been observed to date in this ongoing test. The research conducted by EPI will be presented in this paper.

A hydromechanical framework, for retention compatibility of soil-geotextile filters in cyclic flow, is developed through laboratory test data. Combinations of eight geotextiles and four cohesionless soils were tested in a cyclic gradient ratio permeameter. Interpretation of the results addresses three test variables namely, filter ratio (AOS/D₈₅), hydraulic gradient (i) and confining stress (σ). The framework is found reasonable to explain filter compatibility, and conditions leading to onset of retention incompatibility. For a uniformly-graded soil, the onset of incompatibility occurs at 2 ≤ AOS/D₈₅ ≤ 2.5. Two select retention criteria involving cyclic or dynamic flow are evaluated and recommended for certain types of base soils.

The service life of geomembranes varies significantly based on their exposure conditions. For instance, the service life of polymeric geomembranes exposed to atmospheric conditions with solar radiation, high temperatures, and oxygen is anticipated to be shorter than that of buried geomembranes. Both linear low density polyethylene (LLDPE) geomembranes and high density polyethylene (HDPE) geomembranes are used for exposed applications (e.g., landfill covers, pond and canal liners, etc.). LLDPE geomembranes are very flexible, with a higher tensile break elongation than HDPE geomembranes and, therefore, greater ability to maintain their integrity under localized differential settlement without puncturing, tearing, or cracking. On the other hand, HDPE geomembranes have excellent ultraviolet (UV) and chemical resistance; however, they have low puncture resistance and low multi-axial extensibility compared to LLDPE geomembranes. This paper compares the relative performance of exposed LLDPE and HDPE geomembranes based on laboratory test results and field performance data.

The diffusive properties of thin-layer ethylene vinyl alcohol (EVOH) thin-films often used in vapour barriers and co-extruded geomembranes were studied. Sorption, diffusion and permeation were studied for benzene, toluene, ethylbenzene and xylenes (BTEX) contaminants in dilute aqueous solutions. Films with 32 and 44 mol% EVOH were studied, showing a decrease in permeability with higher EVOH content. Sorption was studied for the EVOH thin-films at room temperature, as well as 30, 40 and 50°C. An increase in sorption of BTEXs was observed at elevated temperatures. Results show that the permeability of these non-polar hydrocarbons decreases with decreasing EVOH content from the 32 mol% thin-film (P_g=15–57 x 10^{– 14}m²s^–1), to the 44 mol% thin-film (P_g=3–5 x 10^–14m²s^–1). When compared with the EVOH inner barrier layer of a co-extruded LLDPE/EVOH geomembrane, the co-extruded geomembrane has the lowest P^g (0.7–0.9 x 10^minus;14m²s^–1). P^g values are significantly lower for EVOH thin-films and co-extruded geomembranes when compared with standard LLDPE, HDPE and PVC geomembranes.

This paper summarizes the results of a laboratory study addressing the cyclic stress-strain response of expanded polystyrene (EPS) geofoam under various confining stresses. Experimental results from cyclic uniaxial and triaxial compression tests conducted in the viscoelastic domain revealed that the normalized shear modulus degradation curve is insensitive to the static confining stress, whereas the damping ratio of EPS geofoam appears to increase with increasing static confining stress. The visco-elasto-plastic response of EPS geofoam also seems to be affected by the magnitude of the applied static confining stress in cyclic triaxial tests. An increase in the static confining stress is associated with a reduction in the accumulated permanent (plastic) strain for a specific number of applied loading cycles.

The soil—geomembrane interface friction is relatively weak, potentially forming the critical failure (i.e., slip) planes and governing the design in structures where the geomembranes are used. Therefore, it is very important to capture the soil—geomembrane interaction at the interface and accurately obtain the interface strength properties. Interface strength properties depend on the contact area and stress at the interface. The materials, such as polyethylene, used in geomembranes exhibit a viscoelastic response to load in the form of material creep and stress relaxation. Considering that all the projects have a design life, the geomembranes will have viscoelastic response and show creep to the loads applied during their service life. It is necessary to understand and quantify the effect of time on soil—geomembrane contact surfaces and shear mechanisms. This paper presents a new theoretical model which incorporates the viscoelastic nature of geomembranes in determining the time-dependent contact areas at the soil and geomembrane interfaces.

Walter and Son Waste Hauling was tasked to hydraulically dredge 11,468 m3 (15,000 yd3) of river sediments (25-percent solids) from a backwater slough adjacent to the La Crosse Wisconsin Municipal Airport for subsequent backfill and taxiway construction using geogrids. Geotextile tubes and a site-specific chemical conditioning program were identified and subsequently implemented as a high volume, high flow containment option that provided efficient, cost effective, and environmentally friendly dewatering. The objective of this project was to design and operate a turn-key dewatering project that used a site-specific chemical conditioning program to expedite dewatering of sediments in geotextile tubes and safely return filtrate water back to area surface waters. Management included a comprehensive design with geotextile tube containment area specifications, weir design, liner and geotextile recommendations, and drawings. Feasibility testing included identification of a site-specific plan, fabric selection, hanging bag performance, Wisconsin DNR use permit applications and additional toxicological evaluation for full-scale operations. Management included technical support for construction, mobilization and start-up, daily and weekly reports, and personnel training for both chemical optimization and geotextile tube management. Overall, turn-key management helped the contractor optimize performance in a timely manner which ultimately led to realized profitability.

A study on dewatering rock crushing fines using geotextile tubes was conducted. Rapid dewatering tests and hanging bag tests were used to evaluate the dewatering efficiencies of the geotextiles as well as the effectiveness of chemical flocculants. Settling ponds are currently the predominant method used to dewater rock crushing fines. Settling ponds effectively dewater the material, but they are relatively slow and require large amounts of land. Recent studies by Kutay and Aydilek (2005), Liao and Bhatia (2005), and Kutay et al. (2005) showed that geotextile tubes can be used to dewater high water content materials. These studies did not address dewatering rock crushing fines. The objective of this study was to assess the dewatering and filtration characteristics of geotextile tubes specifically for rock crushing fines. Tests showed that geotextile tubes effectively dewater rock crushing fines and retain the solid particles. The filter cake forming in the geotextile tube dominates the filtration behavior. The chemical flocculants tested did not improve the dewatering efficiency or the filtration efficiency of the geotextiles.

Geoenvironmental engineers are increasingly being involved in the dewatering, containment, and remediation of high water content geomaterials. Although successful applications of geotextile tube dewatering have been reported, guidance for geotextile selection and characterization is sparse and continues to rely predominantly upon experience and unpublished proprietary approaches. Among the available test methods, the standard Hanging Bag Test and the Pressure Filtration Test have been widely reported in literature to evaluate dewatering performance of geotextiles. This paper presents results from an experimental investigation focused on evaluating the characteristics of five different geotextile materials (three woven, one non-woven and one composite) for dewatering high water content lake sediments using the Hanging Bag Test and the Pressure Filtration Test. Results indicate that both the tests can be used for preliminary screening of candidate geotextiles. Limitations of the test methods are also highlighted.

Canal do Fundão is an artificial estuary created in 1951 when the Brazilian federal oil company (Petrobrás) conducted a land formation project adjacent to the eastern shore of Guanabara Bay in the state of Rio de Janeiro, Brazil. In the years since its formation, several "favelas" (ghettos) evolved near the shoreline of Canal do Fundão and raw sewage began to collect in the canal rather than disperse into Guanabara Bay. The estuary was identified as a major environmental concern impacting health and life. In 2004, the federal government of Brazil funded an engineering investigation to define the restoration of Canal do Fundão. In 2007 and 2008, soil borings and samples were taken from the contaminated areas for analysis. Polymer bench tests via the TenCate Rapid Dewatering Test (RDT) were conducted along with the TenCate Cone Test to qualify polymer type and optimum dosage for acceptable performance. Following these tests, a number of TenCate Geotube Dewatering Tests (GDT's) were conducted to validate the polymer selection and dosage, and to predict the full scale project results and final dewatered solids inside the Geotube® containers. The purpose of this paper will be to detail all of the sample testing, types of analysis and how accurately the TenCate GDT tests predicted the actual project results.

Geotextile tubes have successfully been used by virtually every industry today to dewater a variety of sediments, slurries, by-products, and wastes. Despite this, the dewatering industry currently lacks uniformity in regards to establishing testing standards and assessing dewatering performance. Prior to full-scale tube deployment, lab and/or field tests are typically performed to evaluate performance. Preliminary bench tests such as the falling head test (FHT) and pressure filtration test (PFT) are often used to evaluate candidate polymers and dewatering efficiency. The mid-scale hanging bag test (HBT) and geotextile tube dewatering test (GDT) may then be used to visualize the dewatering process and evaluate the selected polymer. There is currently no industry standard, however, and numerous variations in testing programs, methods, and data interpretation exist. Before advanced studies can be undertaken, a common framework for data interpretation must be created by standardizing testing programs. Using a fine grained, non-plastic soil and woven geotextiles, this study aims to examine and compare the bench-scale and mid-scale test methods adopted for assessing dewatering performance. In addition to standardized testing programs, the need exists for estimating geotextile tube dewatering rates. This study proposes a theoretical model using Darcy's law and the Kozeny-Carman equation which allows for an estimation of dewatering time.

Many types of high moisture content slurries are dewatered in geotextile tubes. Slurries can include dredged sediment from waterways and waste from industrial processes. Tubes can also be very useful for dewatering and containing contaminated sediments. Geotextile tubes have been successfully employed in several large remediation projects. Chemical conditioning of the slurry with polymers can provide many benefits to a dewatering project. The category of polymers covers a wide range of chemical additives including flocculants and coagulants. Polymers can dramatically reduce turbidity in the decant water and can bind solid contaminants with the material being retained. There are many chemicals designed for treating waste streams, having a variety of charges, weights and chemical properties. These will be discussed in this paper, as specifically related to their use with geotextile tubes. The effectiveness of a tube dewatering project is often measured by the retention of solids particles and the rate at which clean water is released. The correct dosage of polymers can control the permeability of the filter cake, which in turn, impacts these two measures of effectiveness. Decant water resulting from the dewatering process must be also accounted for in the project design. If the decant water is contaminated or excessively turbid, chemical conditioning of the slurry prior to being pumped into the tube can be a very effective solution. In the design phase, bench-scale tests are conducted to determine the optimal chemicals and their dosage rate. The use of Buchner funnel tests and hanging bag tests will be described. Case histories will also be presented which describes the use of chemical conditioning with geotextile tube dewatering. Results from several years of testing a wide range of slurries will be compared and contrasted to other literature on the subject. Quantitative results from the bench scale tests will be compared to the full scale results.

Wheel loading is point loading that generates omni-directional horizontal stresses within the engineering fill below the surface and at the interface of this fill with the natural ground. Where the fill is reinforced by geogrids these horizontal stresses are resisted by omni-directional confinement forces in the geogrids. Whilst all geogrids were square-patterned information relevant to these confinement forces could be derived from tensile testing in the two principal directions of the geogrid. However, this does not apply to newer geogrids with triangular apertures. In fact, any uni-directional tensile testing of these products has no relationship to the confinement loads they can generate. Therefore a new test is required to give information on the ability of different geogrids to generate omni-directional confinement loads, such as that introduced at the 9^th International Conference on Geosynthetics in Brazil in May 2010. The test is a modified form of the geomembrane test covered by DIN 61551 in which a circular sample is inflated by water pressure. Since then this test has been applied to a range of different biaxial geogrids of both square and triangular format. Both square and triangular apertures, and both integral and assembled geogrid types have been tested. The results of this testing are reported in this paper and the differences in performance of the different types tested are discussed.

In 2007 we became aware of a number of failures of Thermoplastic Olefin Materials (TPOs) that led us to re-evaluate our use of these polymers. We were witnessing the failure of a series of floating covers in both North America and Australia where we had been asked to provide repair and replacement of floating covers and liners. Although the research at that time was concentrating on UV light resistance as a key failure factor; examples of liners failing in the absence of light led us to look at chlorine resistance as an alternative factor. A key success in our research was the development of a simple test that clearly replicated the failures that we had seen in service. This new test subjected the liner material to a strong chlorine solution at elevated temperature while under stress. This chlorine stress cracking test mirrored the observed steps in the field degradation of TPO materials from loss of stabilizers; to surface cracking; to full failure in a test period of less than 1000 hours. In our evaluation of failed materials we discovered that antioxidant stabilizers were not retaining their effectiveness in the presence of chlorine. Once the stabilizers lost their effectiveness the specimens progressed through predictable degradation stages until cracking occurred. Once we had developed a background of what was causing the problems in these TPOs we started work on the development of an improved formulation. Through the use of our chlorine stress cracking test we were able to clearly evaluate individual ingredients. This gave us the opportunity to determine which ingredients were causing problems; and, more importantly, gave us a method to optimize the formulation of a replacement material. This paper outlines the development of a chlorine stress cracking test, the results of testing from this test, and the development of an alternative chlorine-resistant TPO formulation as a result of the guidelines provided by this test.

A novel technique is developed based on the piezoresistivity of electrically-filled polymers to measure tensile strain in geosynthetics as an alternative method to conventional instrumentation (e.g. use of strain gauges). The paper reports the development of the technique and selected results obtained for polyolefin geogrid specimens filled with carbon black (CB). The proof-of-concept study reported in this paper has two important aspects: 1) strain sensitivity of electrical conductivity was demonstrated in polyolefins that are used to manufacture geosynthetics and 2) this strain sensitivity was obtained and demonstrated over the range of strain values that are important in geosynthetic engineering applications.

This paper will describe the evolution of key industry dewatering tests (Cone, HBT, RDT, and GDT) and their accuracy in predicting full scale results. Geotextile containers for dewatering applications have proven both reliable and efficient. As the use of geotextile containers becomes more prevalent and the overall knowledge of the technology advances, so too do the methods of testing to predict the suitability and efficiency for a specific application. Both bench testing and small scale field testing have evolved.

Hydraulic transmissivity, or the volumetric flow rate per unit width of specimen per unit gradient, is the most important design parameter for a candidate geonet or geocomposite to be used for in-plane drainage applications, such as landfill leachate collection systems or landfill cover drainage systems. The 305 mm wide by 305 mm long box of the American Society of Testing and Material D4716 in-line transmissivity test method has been extensively used to determine the transmissivity of a candidate geosynthetic product over the past one and half decades. However, our study showed that significant effects of the specimen size and the flow direction can be generated on some biplanar geonet or geocomposite samples in D4716 transmissivity tests. The theoretical derivations and actual test results are presented and discussed.

Plasma treatment was done to improve the hydrophobic functions of nonwoven geotextiles. We compared the separation and reinforcement performance through frictional properties, before and after plasma treatment. Friction tests were examined in the interface between geomembranes and nonwoven geotextiles. The frictional performance was analyzed by the peak shear stress and the residual shear stress. The long-term performance of these geotextiles could be determined and analyzed from the experimental results before and after plasma treatment.

The use of the Stepped Isothermal Method (SIM) of accelerated compression creep to measure the time dependent loss of thickness and porosity (and thus flow) of planar geosynthetic drains has increased. As a result, there is opportunity to reach for real-time flow tests at pre-established time-dependent thicknesses. Instead of a time dependent flow test such as the well accepted 100-hour transmissivity measurement, one might achieve the same flow in a very short term test if the thickness of the drain at 100 hours is known and the 100-hour porosity can be established accordingly. The historical challenge associated with this opportunity has been the relative inability to measure the thickness of the geosynthetic drain when encompassed by adjacent materials in the fully designed drainage system as installed in a hydraulic transmissivity test apparatus. Indeed, synthetic geomembranes, filter geotextiles, GCLs and a host of possible cover aggregates and soils interfere with accurate thickness measurements, prohibiting the realization of the necessary thickness vs. flow relationship. Two geocomposite drains were first characterized for their compression creep (thickness vs. time relationship) properties using SIM. The drains were then subsequently tested for 100 hour transmissivity using representative adjacent drainage system components. These 100 hour transmissivity tests were performed using the current industry practice of time dependent flow testing, i.e., 100 hour duration tests. In separate tests, the two drains were positioned in the transmissivity test unit with the same adjacent drainage system components, and then compressed to specified time-dependent thicknesses, including 100 hours, for short term flow testing. Subsequent thickness dependent flow measurements were directly compared to time dependent flow measurements. This paper will present all test results generated, with special emphasis on thickness dependent hydraulic performance relationships to conventional time dependent transmissivity tests. Ramifications of this new testing approach will be explored in the context of existing product specifications, design procedures, and economy of cost.

Four candidate final cover systems were evaluated for closure of a Phosphogypsum stack. The desktop study was to evaluate the system that best meets the objectives of the final cover system, which is to isolate the gypsum material, support vegetative growth, control erosion, have good stability, and be constructible within fiscal restraints. The first candidate system was the base case that used a 24-inch thick layer of silty lean clay soil. The other three included different geosynthetic layers underneath the cover layer, including a textured high density polyethylene geomembrane (HDTGM) layer only, a geocomposite drainage layer overlying a HDTGM, and a geocomposite drainage layer only. The hydrologic performance was evaluated using the HELP model, which provided insight to the level of hydrostatic head building up in the outer cover soil and the quantity of moisture infiltrating into the underlying gypsum. The stability was then evaluated with an infinite slope model, including the level of hydrostatic head that was predicted by the HELP modeling. The two systems that had the best predicted performance were the two that included the geocomposite drainage layer and the preferred system was that having only a geocomposite drainage layer beneath the cover soil.

This paper presents and discusses the results obtained in laboratory tests to evaluate the behavior of filter systems consisting of nonwoven geotextiles overlying different granular materials under confinement. Nonwoven geotextiles with masses per unit area of 200 g/m², 400 g/m² and 600 g/m² were used in the tests. Stainless steel spheres and a coarse aggregate were employed as granular materials underlying the geotextile filter. Specific tests to evaluate the intensity of sagging of the geotextile filter in the voids of the underlying materialwere carried out. Average strains in the geotextile were also obtained in the tests. The grain sizes of the particles that piped through the geotextile filter for different arrangements of spheres as bedding layer for the filter were also assessed. The results obtained showed the influence of the bedding conditions of the geotextile on its deformed shape and retention capacity.

As part of a potable water reservoir project for the Metropolitan Water District of Southern California, Layfield Environmental Systems fabricated and installed a flexible geomembrane defined sump floating cover system. On this project Layfield operated as the general contractor with a scope of work that included removing and replacing the existing floating cover and installing a new 65,000 m² (700,000 ft²) floating cover system. The project also included an additional 28,000 m² (300,000 ft²) of a chafer reinforcement material around the perimeter of the floating cover, rain water removal pumps, upgrading of the existing electrical systems, installation of drain pipes, mechanical work and the design and operation of a temporary water treatment facility. This project encountered some serious installation challenges including a tight 180 day installation schedule as this was a critical reservoir with an operational capacity of 130.4 hectares (326 acre feet) providing treated water to Riverside and San Diego Counties. A special consideration on this project was the requirement to capture all water that was collected from the construction site. This included the design and operation of a temporary water treatment facility as the Regional Water Quality Board had set strict discharge limits on the water released from the site. The water treatment plant was designed to capture nuisance chemicals or contaminants in rainwater as a result of construction. There was also major water leakage of up to 1,135 litres (300 gallons) per minute at the influent and effluent gates requiring continuous pumping and dewatering strategies throughout the duration of the project. The project was further challenged by excessive poor weather as part of an El Nino year in California. This paper discusses the various technical challenges and the innovative design and project management solutions incorporated to help finish the project on schedule.

Biogas collection and use from industrial and agricultural sources is a rapidly growing use for fabricated geomembrane floating covers. Most successful biogas collection projects in recent years have been on larger projects where the scale of the project allows for significant research and design expenditures. The need exists for a less expensive biogas collection solution for smaller farms. While State and National agencies work to develop protocols for using the biogas collected from small farms the development of biogas collection covers that meet the requirements of small agricultural projects has not kept pace. This paper presents the current state of the development of covers for small confined animal feeding operations (CAFOs) with an emphasis on manure slurry storage applications. The problems with providing a cover for slurry storage will be outlined and the areas requiring solutions will be identified. An innovative design for prefabricated manure slurry storage biogas collection covers will be presented. The testing that went into the development of this new patent-pending cover design will be reviewed. Current biogas collection cover designs are not well matched to the small agricultural livestock producer. Small livestock producers have little capital available to design or purchase covers and current biogas cover designs are not matched to existing manure management practices. This paper presents the issues surrounding biogas collection for small livestock operations and an innovative fabricated geomembrane biogas collection cover that addresses these issues.

This paper describes the use of a flexible membrane cover to prevent the introduction of rain water into landfill leachate collection ponds in areas that experience high annual amounts of rainfall to reduce overall operation cost related to the treatment and disposal of the leachate. The project involves the Olympic View Sanitary Landfill which has a leachate pond with a capacity of 8,990,353 liters (2,375,000 gallons). The pond has a 4,886 s.m. (52,598 s.f.) surface area and experiences an average annual precipitation of 1,369 millimeters (53.9"). This paper discusses membrane material selection and testing, overall design requirements, necessity to accommodate existing equipment, floating cover and accessory fabrication methods, and installation methods used to overcome the restriction of maintaining leachate pond service during the project. This approach to covering leachate ponds has benefits that may be realized on other installations and it can be adapted for methane gas collection or emissions and odor control as well.

This paper presents an attempt to evaluate the feasibility of predicting the K₀ value of natural soil deposits on the basis of the measured shear wave velocities from the seismic piezocone penetration tests (SCPTU). The original relationship between K₀ and the shear wave velocity established based on the existed test results was used to predict K₀ of those two well-documented sites. Shear wave velocities from both cross-hole seismic and SCPTU were used. A good match between prediction and measured test results of this study explains the versatility and potential of SCPTU method to interpret K₀ of both clayey and sandy soils. Eventually, effects of soil types and OCR on the comparisons are also discussed, and the relationships between K₀ and OCR have been proposed for the two soil deposits.

Measurements obtained during cone penetration testing can be strongly affected by the drainage condition and anisotropy of the soil being penetrated. The cone penetration test is analyzed herein using cylindrical cavity expansion within the explicit, finite-difference continuum mechanics program FLAC. The MIT-S1 constitutive model is used to simulate the anisotropic behaviors of sand and clay during cone penetration testing at varying penetration rates. The response of the soil during cavity expansion is examined at both the material level and spatially for loose-of-critical clay and dense-of-critical sand. Complexities in the response are presented and discussed.

This paper describes a site investigation performed at a sand and gravel quarry in Griffin, IN. Cone penetration tests (CPTu), vision CPTu (VisCPTu), seismic CPTu (SCPTu), and flat plate dilatometer tests (DMT) were performed. The high density and diversity of in situ tests provide an excellent opportunity to compare liquefaction susceptibility predictions using various tests. The availability of video image data offers a unique opportunity to augment the more conventional tests. The vision data provides a qualitative liquefaction hazard prediction, as very loose, liquefiable deposits show local liquefaction near the camera by way of observed soil movement during pauses in the cone's advance. Results show that current CPTu-based liquefaction assessments predict the highest liquefaction susceptibility in clean sand deposits. However, DMT-based liquefaction assessments predict the highest liquefaction susceptibility in gravelly sand.

Cone penetration tests (CPTs) have been performed on very soft marsh and foundation soils in support of the dike design of two containment areas for a liquefied natural gas (LNG) terminal in Georgia. Due to the inherent variability in layer thickness and soil classification within a CPT sounding profile, an algorithm has been written to automate the CPT sounding analysis. The algorithm was initially written to automate the data interpretation process (i.e. soil classification and strength evaluation) and was later expanded to (i) evaluate strength gain and (ii) estimate settlement using CPT profiles. The algorithm uses CPT profiles (obtained at the same location during different time frames) that are analyzed through signal processing techniques incorporated in the code. The signal processing techniques used include high frequency filters and a series of cross-correlation techniques. The algorithm also incorporates a series of curve fitting techniques to evaluate the profiles as a function of depth. This paper provides an overview of the techniques used in the algorithm along with strength gain plots.Comparison between settlements estimated using the CPT soundings through signal processing and settlements calculated using conventional theories are also presented. The comparison shows favorable agreement between the two techniques.

Seismic cone penetration test (SCPT) is an effective method to determine the shear wave velocity of in-situ subsurface materials. In Hawaii, highly variable subsurface conditions with boulder content and Intermediate Geo-Materials (IGM) are prevalent; therefore, this method can become very problematic and time consuming to perform. When these hard zones are encountered in the subsurface, the seismic cone penetrometer cannot advance into the material for testing until drilling methods are used to advance into and past the hard zones. In order to efficiently perform SCPT in these problematic conditions, especially IGM, a different method of shear wave velocity profiling using the seismic cone penetrometer in bentonite backfilled boreholes is presented. A side-by-side comparison study was conducted in natural ground and through a bentonite backfilled borehole to determine the effect of the bentonite on the shear wave velocity test results. Results of the side-by-side comparison are presented and discussed. Based on the results, the alternative method of SCPT in bentonite backfilled boreholes is an acceptable method in these difficult subsurface conditions.

This paper describes the application of maximum log-likelihood estimation to estimate the average force during a dynamic penetration. It is used to obtain a quasi- static equivalent of the dynamic force in Rapid Soil Characterization System (RapSochs). The force is measured at the tip and friction sleeve by strain gauges during hammer blows. The results are necessary for any analyses similar to Cone Penetration Test (CPT) data analysis. This method is proven to result in an acceptable estimation of the force (the soil resistance) in different soil types. It is shown that the cone resistance, friction resistance and friction ratio similar to CPT can be obtained and these are plotted versus depth. It is also shown that the estimated soil resistance does not depend on the applied energy and variable hammer drop height.

Since the earliest days of geotechnical engineering, soil properties developed during the site characterization phase of a project have typically been viewed as fixed quantities independent of the deterministic analyses in which they are eventually used. This paper explores the premise that given all the advances that have occurred in geotechnical engineering what is needed in both routine practice and research alike is a fundamental change in philosophy to one that links or couples site characterization outcomes and analytical theories in a seamless, integrated, dynamic fashion to converge at a unique final result that contains the desired answer to the analysis. The application of this concept to the common foundation engineering problem of bearing capacity of a spread footing is presented in detail to illustrate the process. Noteworthy is the fact that no unusual or sophisticated exploration, testing, or analytical tools are required which means this new conceptual approach is immediately applicable to the simplest of projects and on a routine basis.

Construction of power plants is being considered at three sites located on the floodplain of the Ohio River. The results of a comprehensive subsurface investigation show that all three sites are fairly similar in terms of subsurface profile, consisting primarily of thick fluvial sand deposits composed mostly of medium to coarse sand with small amounts of silt and gravel. Assessment of soil properties, including relative density and effective stress friction angle, was made by applying various empirical or semi-empirical correlations to field and laboratory measurements. By comparing the results given by the different correlations, their relative accuracy at these sites is evaluated.

The Panama Canal's Third Set of Locks project will be constructed east of the existing Gatun Locks on the Atlantic side and southwest of the existing Miraflores Locks on the Pacific side. The project was designed to take advantage of the excavations that were started by the Americans in 1939-1942 and were interrupted by the onset of World War II. Since that time, and more recently in 2001 and 2005 through 2008, several geologic and geotechnical investigations were carried out including thousands of core borings, geophysical studies, in-situ testing, geological mapping and laboratory testing. All these data have been used to characterize the site and foundation for the new lock structures. This paper describes the geologic setting and characterization of the sites where the new locks for the expansion of the Panama Canal will be constructed. The evolution of the various sets of subsurface information, dating from 1939 through 2008, is discussed. A description of the components of the Third Set of Locks project and the geologic conditions associated with these components are highlighted.

Soil is a natural material having varied properties which changes both along the depth and width of the stratum. To know the engineering behavior (e.g. bearing capacity) and nature of the soil, site investigation is recommended. However, for a highly populated city like Mumbai in India, many times it is bit difficult to carry out such site investigation to obtain the exact soil profile at all locations. In this paper, Geographic Information System (GIS) and Global Positioning System (GPS) are used to obtain the soil index property maps for Mumbai city, which is the financial capital of India. These maps will be extremely useful for obtaining a gross overall view of soil index properties of various locations of Mumbai. About 450 numbers of soil testing reports were collected from several geotechnical laboratories and professionals to create a huge soil database of Mumbai city. The integration of GIS, GPS and database of properties of soil such as specific gravity, moisture content, ground water level, liquid limit etc. will be very helpful to the soil investigators, geotechnical engineers and contractors working in Mumbai region for understanding the soil strata to decide the location for a future structure based on geotechnical engineering design.

This paper presents a site characterization case history for an 11.6-km (7.2-mile) fixed-guideway transit system in the corridor between East Kapolei and Pearl Highlands, on the Island of Oahu, Hawaii. The relatively young age of the volcanic island and the sea level fluctuations during the continental glaciation cycles produced complex subsurface material combinations, which is unique only to Hawaii. As a result, subsurface material distribution and their engineering properties could vary significantly within short distances and are hard to predict accurately. A carefully selected sampling/testing program was implemented to provide a conceptual vision into the subsurface profile and to estimate the subsurface material properties and their engineering performance. The subsurface exploration program included conventional approaches (i.e. soil borings, SCPTu, SSWV, and ReMi^TM) but with some variations to account for local conditions and practices. From the generalized subsurface profile along the project alignment, the profile indicated variable distribution and material properties in the subsurface typical of the highly variable ground conditions encountered in Hawaii.

In the last two decades, Cone Penetration Test (CPT) based analysis and modeling became a popular and handy tool for geotechnical engineers for subsurface investigations and soil characterization. Several CPT soil classification methods gained wide acknowledgement for this type of analysis including the Schmertmann (1978), the Robertson et al. (1986), and the Zhang and Tumay Probabilistic (1999) methods. Most of the CPT-Based analysis software packages use one or more of these methods to analyze and model data sets. However, there is no visual method available that can provide an analysis and combined presentation using different methods. Considering the individual strengths and weaknesses of the methods, using a comparative and collective approach can provide a more realistic interpretation and analysis of data sets. This paper presents a practical visual presentation approach that utilizes different characterization methods and provides a collective but clear presentation. The approach uses a new standardized color coding system to achieve comparative and comprehensive presentation of the model results. Modeling and analysis of two sample sites are included in the paper to illustrate the approach.

This paper discusses the use of "compaction control" for controlling swelling behavior of the expansive clays in Nandipur (North Eastern part of Pakistan). A highly plastic and swelling clay. The problem of the expansive soil of Nandipur came into picture during geotechnical investigation in this area for a proposed road. The effect of compaction control on the swell potential was investigated for suggesting a cheap remedial measure for the expansive soil encountering the road in Nandipur region. Soil samples from the site were compacted at various compaction energies and at various moisture contents and then tested for free swell and swell pressure. Finally, the best range of moisture content and compaction energies were suggested for the Nandipur soil that gave the minimum swell potential

The expansion potential (EP) of a soil or sedimentary bedrock formation defines the severity of risk related to slab or foundation movement due to heave of expansive soil or bedrock. Common practice is to categorize the risk potential solely on the basis of the percent swell that a soil sample exhibits in the consolidation-swell test. However, calculations of heave take into account both percent swell and swelling pressure. Therefore, assessment of risk must consider both of those factors. A risk factor termed "Expansion Potential", EP, considering both percent swell and swelling pressure is defined in this paper. Values of EP computed using a database collected from results of numerous consolidation-swell tests show good correlation between predicted heave and EP. The use of EP will provide a more accurate description of the actual risk of the potential for slab or foundation movement. Measurements of slab and foundation actual movement are presented and correlated to EP. These results confirm the conclusions drawn on the basis of computation for uniform soil profiles.

Shear strength, compressibility, and permeability are three important properties of a soil mass. The geotechnical properties of a soil mass depend on the dominance of soil mineral in it. Forty different mixtures of Montmorillonite, Kaolinite, Illite, and Quartz were prepared to evaluate the liquid limit, plasticity index, clay sized fraction, activity, compression index, swelling index, and permeability. This study presents the variation of compressibility and permeability of soil with the proportion of minerals and relationship of compression index with liquid limit, activity and clay sized fraction. The research result shows that compression index exhibits a reasonably good relationship with liquid limit.

The high initial cost for a deep foundation system with a structurally suspended floor slab for light commercial and retail buildings on expansive clays would make many, if not most, projects economically prohibitive. Reality is that such structures are commonly supported on a hybrid foundation system where exterior walls and interior columns are supported on a relatively deep foundation system, and the floor slab bears on a pad of fill on expansive clays in the active zone. Most foundation systems of this design experience tolerable movements, but some experience significant distress resulting in damaging the building. This paper presents case studies on common design and construction defects (some would appear minor) that can contribute significantly to distress, and offers suggestions to address these issues.

The depth of the active zone under a "mature" tree in an open field will stabilize somewhat, and moisture variations within the active zone will primarily occur due to seasonal moisture variations. However, the depth of the active zone will grow, and the horizontal extent of moisture variations will change due to the long term growth of trees. This effect is particularly dynamic in the urban environment where recharging of the subsoils during wet periods is often restricted by the presence of paving and buildings. Long term moisture losses due to trees caused three 9 foot (2.7 m) deep underreamed piers supporting a 4-story building to settle between 3 and 5 inches (8 to 13 cm) at a site in Southeast Houston, Texas. The total settlement of the ground surface under the floor slab was ±8 inches (20 cm). The commonly accepted depth of "seasonal moisture change" in this area of Houston is 6 ± 2 feet (1.8 ± .6 m), but the depth of the active zone was found to be ±28 feet (8.5 m) due to moisture demand of the trees.

This investigation involves characterizing and evaluating the expansion potential of several clayey soils from the area of Boquerón, Cabo Rojo, in southwest Puerto Rico. The samples were collected from two test pits excavated as part of this project and were also obtained from a geotechnical consultant that had performed a study in the vicinity of the test pit locations. The experimental program involved in- situ field tests and laboratory tests on selected representative samples. The laboratory program involved geotechnical classification of the soils, gradation, Atterberg limits, mineralogy characterization, and specialized tests for assessing swell potential of clayey soils. The mineralogy characterization involved determination of specific surface area, cation exchange capacity, and X-Ray diffraction. Results from these tests revealed significant presence of montmorillonite. The mineralogy combined with test results of swell pressure and free swell revealed that some of the soils tested from the test site Cabo Rojo can experience free swell volume changes greater than 40%, and swell pressures greater than 32,000 psf. The results of this investigation confirmed presence of highly expansive soils in this test area located in the southwest region of Puerto Rico.

In marginal soils, it is common to use chemical stabilizers to improve the strength properties of those soils for roadway construction. Many departments of transportation have a standard or design guide that is used to determine the stabilizer type (i.e. Lime, Fly Ash, Cement Kiln Dust, etc.) and the amount of stabilizer to use based on soil classification. These design guides do not always provide an ideal stabilization design since only a few index soil properties like Atterberg Limits and grain size distribution are used for soil classification. The testing in this study involves five roadway construction sites where the use of Class C Fly Ash (CFA) as a stabilizer and quicklime as a modifier to reduce Plasticity Index (PI) and increase workability was performed. The roadway sites were tested with the Dynamic Cone Penetrometer (DCP) and unconfined compression strength (UCS) specimens were prepared to match the cure times of the field testing. The results of this research show that the DCP can be effectively utilized to verify strength gains of stabilized roadway subgrades and that the change in Average Dynamic Cone Index (DCI) could possibly be correlated to strength increase results from laboratory UCS testing.

In this study, the causes of distress (cracks and joint movement) on the face panels of an 244 m (800 feet) long and 4.6 m (15 feet) high retaining wall supporting a highway embankment was investigated by instrumenting the ground in front of the wall. The foundation of the retaining wall was placed in a CH soil few feet below the surface and ground water table was about 7 feet (2 m) below ground. In order to determine the vertical and horizontal ground movements in the active zone and to determine the variation of matric soil suction adjacent to the wall total of three boreholes were instrumented. Also changes in temperature and rainfall were also monitored during the study period. The ground and wall crack movements were measured for about two years which included also the hurricane Ike. The instrumentation included tensiometers, extensometers and an inclinometer. Based on the measurements over period of one year, largest vertical and horizontal displacements were observed in the top five feet of the ground. The tensiometer was used to measure the matric suction pressures during this period. The change in the length of the crack opening varied with the climate and it was similar to the settlement in the active zone. Typical measured changes in the crack along the wall varied from 0.2 mm (opening) to –0.4 mm. Effect of climate changes on the distress of retaining wall was also evaluated using the Thornthwaite moisture index (TI). TI was also used for to predict the suction pressure in the ground.

It is estimated that there is nearly one million miles of drinking water pipelines in the U.S with an asset value of a few trillion dollars. The ASCE Infrastructure Report rates the water infrastructure to be D^–1 and hence there is need to investigate the conditions of the water pipelines. Based on our recent survey, most of the small diameter water pipelines in the major cities are placed within the top 1.5 m depth below ground surface. Hence the water pipelines that are buried in the active zone will experience notable changes in the soil moisture content over the year. In the active zone, soils would be affected by the environmental conditions. In this study, national survey results are presented and analyzed to determine the trends in the water pipeline failures. Based on literature review and experience, potential modes of failures for the small diameter water pipelines have been identified. In the survey conducted by the U.S. Conference of Mayors (USCM) has shown that 20 cities are reporting over 500 water pipeline breaks per year, and the CIGMAT survey showed that this could be much higher in some cities. A few case studies on water pipeline failures in the active zone in the City of Houston, Texas have been discussed.