Geo-Chicago 2016: Sustainable Materials and Resource Conservation

The present study deals with investigating the influence of oxide compositions (viz., SiO₂, Al₂O₃, Fe₂O₃, CaO) on the mechanical behaviour of geopolymer concrete made of fly ash. The study has been carried out employing the extensive data collected from the literature. Trends between 7 and 28 day compressive strengths versus individual oxide composition were developed using the data. In general, the strength of geopolymer concrete found varying greatly with the individual oxide composition and its content. It has been particularly observed that the final compressive strength of concrete is predominantly influenced by SiO₂ and Al₂O₃ contents as compared with CaO and Fe₂O₃ contents, which showed an insignificant effect. As such, results demonstrate that oxide compositions can influence the mechanical behaviour of geopolymer concrete to a greater extent.

This paper presents the engineering properties of a lightweight-foamed glass aggregate (LWA-FG) for consideration as a lightweight fill material for use in retaining structure, embankment, highway, and bridge abutment construction in the United States. A laboratory study was conducted to evaluate the effect of compaction energy on the gradation, compression and direct shear strength of LWA-FG produced in the United States by Aero Aggregates, LLC. Dry and wet particle-size analyses were conducted before and after each of the engineering property tests to determine the amount of particle breakage due to the crushing effect of the impact and vibratory compaction, static compression, and/or direct shear testing. The results indicate the normally uniformly graded LWA-FG (as produced) transforms into an increasingly well graded material as a function of increasing compactive effort, static loading, and shear conditions. Therefore, the engineering properties of unit weight, compressibility, and shear strength of the LWA-FG are directly influenced by the amount of particle breakage and changes in particle distribution during processing. Useful laboratory test data for comparison to field observations and measured field performance are provided from this limited study.

This paper focuses on evaluating the compaction characteristics of untreated and treated red mud waste in a comprehensive way. Chemical solutions such as NaCl and HCl were used to treat the red mud waste. A series of standard Proctor (SP) and modified Proctor (MP) compaction tests were conducted on identical samples of (a) untreated and (b) NaCl and HCl treated samples. It has been observed that among standard Proctor and modified Proctor test, the latter one yields reproducible compaction curves especially on untreated red mud waste. The results also showed significant variations in the value of maximum dry density and optimum water content between NaCl and HCl treated samples. Further, it has also been found that compaction energy can considerably influence the density characteristics of the red mud waste.

In India, enormous quantity of stone dust is produced from the crushing of stone at quarry sites. In the direction of sustainable development, it is desirable to use stone dust to the maximum extent in the construction activities. A series of compressive strength tests have been performed on newly developed construction material (NDCM) prepared using stone dust, expanded polystyrene (EPS) beads and binder material such as cement. Two different densities of EPS beads 22 kg/m³ and 16 kg/m³ were used in the study. The mix ratio percentages used in the study are 0.25, 0.75, and 1.25. The compressive strength of material was evaluated for curing periods of 7, 14, and 28 days. For a particular mix ratio value, compressive strength of material increased with increasing curing period and for a particular curing period value it decreased with increasing mix ratios. The density of NDCM was found to be decreased with increasing mix ratios for both the densities EPS beads. For a particular mix ratio, NDCM prepared using EPS beads of density 16 kg/m³ shows lower density that that of prepared using density 22 kg/m³. For a particular mix ratio and for each curing days, NDCM prepared using EPS beads of density 22 kg/m³ shows higher compressive strength than EPS beads of density 16 kg/m³.

Beneficial use of municipal solid waste incineration (MSWI) fly ash in road construction depends on the geotechnical properties required for performance. Geotechnical properties of aged MSWI fly ash samples were investigated through a series of laboratory tests. Physical properties of the aged MSWI ash closely resemble those of silty sand, with particle sizes ranging from 0.002 mm to 15 mm, specific gravity of 2.68-2.74 and maximum dry unit weight of 10.0-10.5 kN/m³. Hydraulic conductivity ranges from 10^-4 cm/s to 10^-6cm/s, which is similar to fine sands, silts and silty clays, and can be rated as “poor” drainage capacity. California bearing ratio (CBR) tests demonstrate that the CBR of aged ash samples is around 10 or higher, which can be rated as “fair-good” for fill and subgrade/subbase. Unconfined compressive strength is around 300 kN/m² and reduces by less than 2% after 10 freeze-thaw cycles, indicating that the aged MSWI fly ash is durable with respect to freeze-thaw. Based on the tested geotechnical properties, the aged MSWI fly ash is recommended as an alternative lightweight material for fill and subgrade/subbase.

The increased use and production of plastic in developing countries is a growing concern, as the technology of their waste management infrastructure may not be developing at an appropriate rate to deal with the increasing levels of plastic waste. This paper presents the results of the investigation of the engineering behaviour of Ogbese river sand (specific gravity-2.63, fine gravel content-2.72%, sand content-97.28%, AASHTO classification-A-3(0)) stabilized with shredded polyethylene terephthalate (PET) water bottle waste and Portland cement. The goal of this research is the beneficial reuse of the enormous discarded PET plastic waste generated in Nigeria in civil engineering works. The PET water bottles were shredded into strip sizes ranging from 0.3cm × 0.3cm to 0.7cm × 0.7cm. The soil was mixed with PET strips of 0.4%, 0.8%, 1.2%, 1.6%, and 2.0% by weight of soil and 3% cement by same weight of soil. The cement acted as a binder for sand-PET mixtures. Sand-PET-cement mixtures can be used for road pavement base and sub-base course that requires subsurface drainage and as lightweight backfill for retaining structures, due to its favourable strength and permeability characteristics. However, the long term durability and sustainability of soils stabilized with shredded PET wastes in different geologic/hydrogeologic conditions should be investigated before using them in practice.

“Tunable” clay-polymer composites were created as a material that could be modified in-situ through controlled manipulation of interparticle spacings by exposing them to differing surrounding fluid chemistries. Altering interparticle spacing has a significant influence on the mechanical behavior of the composite. The purpose of this study is to investigate the stress-strain response of a kaolinite-polyacrylamide when exposed to various pore fluid conditions, namely ionic concentration (0 M and 0.3 M NaCl). The low and high ionic concentrations were chosen to promote extended and coiled conformations (polymer molecule shape). The specimens of composite and pure kaolin were pre-consolidated at 100 kPa from slurries. The undrained shear strength was determined using triaxial testing in which the specimens were isotropically consolidated to the desired stress of 100 kPa. The results show that the undrained shear strength of the pure kaolinite is controlled mainly by its initial packing density and fabric arrangement (physical effects) rather than any changes in physicochemical-induced forces at the particle level. However, the undrained shear strength of the “tunable” composite was significantly influenced by the conformation of the polymer molecules. In addition, the effective stress path depends on the fabric for pure kaolin and on polymer conformation for the composite, demonstrating the “tunable” nature of the composite.

The produced recycled concrete aggregate (RCA) often is stockpiled at the facility at which is produced and is maintained for more than a year before the material is utilized. This time period is referred to as aging in this study and this article is describing a methodology developed to simulate aging of RCA under laboratory conditions and its effects on RCA’s physical properties and characteristics of leachate extracted following batch water leach tests. The laboratory aging tests were performed for a period of one year. When samples of aged and non-aged RCA were compared, it was observed that unlike aged RCA, non-aged RCA has a measurable plastic limit. This is attributed to the existence of un-hydrated cement paste, which hydrates with aging. The data showed that the changes in other physical properties and mortar content were negligible. However, there were notable differences in the collected leachate. A decrease in pH was observed over time, which is attributed to an increase in carbonate content of the material. The leaching concentrations of Ca, Al, and Fe fluctuated within the first two months and approached to a steady value thereafter. However, the leached concentrations of Mg showed slight but consistent increase with time.

In the ever expanding quest to understand the nature and behavior of soil, translucent and even transparent media have been developed to serve as soil simulates. These artificial soils can be used in experimental models to make visual measurement of phenomena such as geosystem kinematics, soil mass movement, soil particle motion, and pore fluid flow that would be nearly impossible to obtain in natural opaque soils without expensive equipment or boundary effects. One successful type of translucent clay simulate is lithium sodium magnesium silicate (LNM silicate); however, it’s low density/high void ratio results in higher than typical permeability, low undrained shear strength, and extremely long consolidation times. Until now, translucent soil simulates of only 4.5% by mass LNM silicate to total mass have been possible. This paper provides a method for creating mixtures of translucent LNM silicate gel/glass as high as 15% by mass with the additions of an emulsifier, sodium pyrophosphate decahydrate (SPP), which impedes gelation so additional silicate powder can be added. Further, digital image processing techniques are used to present a relationship between LNM silicate, SPP, and translucency and an analysis of the modified simulate’s permeability and consolidation properties, with comparisons to natural clays, is also included.

Air Station Elizabeth City in North Carolina is one of the largest air stations that operate Coast Guard and civilian crafts to meet the need of the Coast Guard and the regional airport. The air station has two major runways, 10-28 and 1-19, along with a taxiway system. Runway 10-28 is in considerably good condition while runway 1-19 is severely deteriorated and in need of repair. Runway 10-28 is currently heavily used resulting in additional stresses on the pavement that ultimately decreased its service life. After the most recent assessment, it was recommended that runway 1-19 be demolished, redesigned, and reconstructed using approximately 75% of the recycled Portland cement concrete (PCC) pavement, upgrade the taxiway system, and improve the storm water management system in order to accommodate the current and future Coast Guard aviation needs. The new layout and pavement design of the taxiway and runway were based on the Federal Aviation Administration and Department of Defense’s unified facilities criteria. The final runway design incorporated an 8 inch aggregate base layer overlaid by a 12 inch thick PCC slab. A new drainage system was designed using the storm water management model (SWMM) to collect and channel storm water runoff generated by the airfield as well as optimize the drainage system to protect the integrity of the runways and reduce maintenance costs.

This paper investigates complete recycling and utilization of waste concrete, both the aggregates and the fines from crushing, to produce new concrete through geopolymerization. Based on previous studies and considering the workability of the new geopolymer concrete (GPC), 25% waste concrete fines (WCF), and 75% class-F fly ash (FA) were used as the geopolymer cement source material, NaOH/Na₂SiO₃ solution as the alkaline activitor, and the aggregates (both coarse and fine) from waste concrete crushing as the aggregate. The research systematically studied the effect of different factors on the initial setting time and the 7-day unconfined compressive strength (UCS) of the GPC. Based on this study, it can be concluded that waste concrete can be completely recycled and used to produce new geopolymer concrete with required UCS values.

This study was performed to show the effects on green bean growth when incorporating different sizes and different percentages of shredded rubber tire into local soil found in Memphis, TN and the surrounding area. Approximately 300 million tires are disposed of each year in the United States which has led to significant environmental concerns. As a remediation to this negative environmental impact, the geotechnical engineering community has been working to use rubber tires as a fill material in soil modification projects. The next concern is the short and long-term effect on plant life due to the incorporation of shredded rubber tire into the soil. In this study, the effect of the rubber tire usage as a fill material on green bean growth was monitored to gain insight on the short-term condition of sight landscape and fruit cultivation. Brown loess, which is the primary soil found in the Memphis area was used as the potting soil. To gain understanding on the use of shredded rubber tire as a fill material, different percentages of varying mesh sizes of shredded rubber tire were mixed with the local loess to form a basis of comparison. The results presented show the effect of different amounts and sizes of shredded rubber tire on the growth rate of green beans.

In this study, the joint activation of fly ash/ground granulated blast furnace slag (GGBS) mixtures has been evaluated in order to find its suitability in geotechnical and geo-environmental applications. Unconfined compressive strength (UCS) tests have been conducted on fly ash/GGBS mixtures prepared at their respective optimum moisture content (OMC) and maximum dry density (MDD) and cured for different periods. The mixture consisting of 70% fly ash and 30% GGBS developed better strength than either of the individual materials. Thereafter, 70:30 mix of fly ash and GGBS was selected for use as binder material for the stabilization of contaminated and expansive soils. With a view to stabilize contaminated soil, the adsorption characteristic of lead ions onto the mixture was determined through batch tests conducted at different pH and time intervals. It was found that the removal efficiency of the lead ions by the binder was comparatively high when compared to fly ash alone. The kinetic studies suggested that the reaction involving the adsorption of lead ions followed second-order kinetics. In the stabilization of expansive soil, the results demonstrated improvement in the plasticity characteristics of the expansive soil as well as reduction in the swell potential. Based on the results obtained in this present study, it can be concluded that combined use fly ash and GGBS can be advantageous when compared to using them individually.

This study investigates methods of improving fine dredge material for use as fill material. Dredging is common in port cities, creating the need to store or use large volume of soil. While the dredge material’s coarse fraction is typically used in transportation applications, the fine dredge material has limited utility and often requires storage. Fine dredge storage in Duluth, Minnesota is limited, increasing the need for reuse. The city is targeting former industrial areas for redevelopment, generating significant requirements for fill. The authors investigated methods of improving Duluth fine dredge material, classified as SM by the unified soil classification system, through combination with several locally available, inexpensive materials, including fly ash, lime kiln dust, taconite mine tailings, and recycled tire. Fly ash and lime kiln dust were not effective in raising hydraulic conductivity to minimum requirements. Additionally, already elevated pH levels in former industrial areas led to environmental concerns with fly ash use. Combinations of approximate two thirds coarse borrow, in this case taconite mine tailings or recycled tire, and one third fine dredge material provided a method of reusing materials to create engineered fill material.

In this study, new innovative geocells were created using recyclable polyvinylchloride (PVC) sheets by simple lamination. These geocells were used as facing of retaining wall models for laboratory shaking table tests. These geocells were honey-comb shaped and the pocket-size of the geocells was maintained as 100 mm. To understand the performance of the geocell walls to seismic shaking conditions, shaking table tests were carried out on retaining wall models created using new geocells and geocells made out of HDPE nets. Geocells were filled with sand or gravel in different tests. These geocell walls were subjected to different levels of seismic shaking by varying the acceleration and frequency of the shaking. Performance of the walls was monitored in terms of wall deformations and accelerations at different elevations. Similitude laws were used to correlate the model tests to field scale retaining walls. Comparison of results with HDPE geocells and PVC geocells showed that the newly created geocells are strong enough to sustain high seismic accelerations without getting damaged. It was the confinement effect created by the geocells, that is responsible for the performance of the geocells and the confinement effect is not too sensitive to the tensile strength of the geocell material, as observed from the tests.

The optimum dimensions of narrow backfill width gravity retaining walls backfilled with recycled materials are obtained by considering the four modes of failure, viz overturning of the wall about its toe, sliding of the wall on its base, eccentricity of the resultant force and bearing capacity failure below the base slab. An analytical method is presented to obtain a solution for the active earth pressure exerted by the backfilling of recycled materials like bottom fly ash, course coal refuses, foundry sand, foundry slag, mill tailing, scrap tires, reclaimed asphalt pavement (RAP) and recycled concrete aggregate (RCA). The proposed method uses the limit equilibrium method with planar slip surfaces. Three different failure mechanisms of the active wedge are considered, namely mechanism 1 (active wedge formed by a single block), mechanism 2 (active wedge is composed of two rigid blocks, one slipping with respect to the other) and mechanism 3 (which considers three blocks). Using these three mechanisms, the magnitude of active earth pressure acting on the gravity wall and point of application of active thrust from the bottom of the wall are computed. The influence of various parameters on the optimum dimensions of the gravity retaining wall is presented in the form of design charts.

Fly ash is a by-product of the coal combustion in electric power generating plants and can be used efficiently in controlled low strength materials (CLSMs). This paper presents an experimental study using locally available class F fly ash to produce a suitable CLSM mixture as a backfill for construction of a laboratory full-scale bridge abutment. The ability to use large volumes of by-product fly ash in the CLSM backfill translates into the potential for a sustainable design by reducing the demands on landfills, where these materials might otherwise be deposited, and conserving the natural aggregate resources. The required time for building bridge abutments can be shortened using CLSM as a flowable and self-compacting backfill material because they do not require controlled compaction of soil layers. The main performance properties for selection of a potential CLSM mixture were compressive strength to support the bridge loads, and flowability to fill the entire abutment in one continuous pour.

This study assessed the use of plastic waste in engineering applications where sulfuric acid attack is crucial, namely, pipes. Cubic specimens were prepared by simultaneously heating and mixing disposed plastic bottles and containers with sand at a temperature that would melt the thermoplastic materials and achieve a uniform fused mix, known as plastic-based cementitious (PBC). Specimens were subjected to sulfuric acid solutions and then tested to determine volume changes, mass changes and compressive strength. Small size pipe samples were molded and tested for maximum bearing strength by the two-edge bearing test and for tensile strength using the indirect tensile strength. The laboratory results revealed that PBC specimens produced with sand had a compressive and tensile strength as high as those using ordinary Portland cement and that small size pipes provided acceptable bearing strength. PBC pipes were also tested for sulfuric acid attack. Findings showed that PBC pipes were highly resistant to sulfuric acid attack. PBC not only has the mechanical properties of concrete and performs well in sulfuric acid solutions it also utilizes recyclables plastic that would otherwise end up in landfills.

Rock quarry dust or quarry dust is produced as solid wastes during crushing of rocks to obtain aggregates. This waste product is left in huge heaps in the neighborhood of the quarry causing serious space problems and health hazards. Further, this waste disposal is another problem faced by the industry. Geotechnical characterization of quarry dust and its interaction behavior with soils can lead to a viable/beneficial solution for its large scale utilization and disposal. Past studies clearly indicate that the quarry dust has a beneficial effect on different geotechnical properties of soil. Therefore, the present study attempts to review the findings reported in the literature to reveal the influence of quarry dust on different geotechnical properties of soil. The study discusses the effect of quarry dust on the specific gravity, liquid limit, plastic limit, shrinkage limit, compaction characteristics, California bearing ratio, shear strength unconfined compressive strength, Young’s modulus, Poisson’s ratio, permeability, swell strain, swell potential, swell pressure etc. of cohesive soil. The review clearly highlights that quarry dust is a promising geo-material for improving the geotechnical properties of soil.

The present study elaborates the preparation of large volume sand bed at different height of fall and deposition intensity for two different types of Indian River sands using the air pluviation methodology. Reconstitution of sand bed is crucial in case of model scale testing to produce the outcomes ensuring repeatability and reproducibility. A systematic study has been carried out in order to determine the optimized area of orifice opening which can fetch the maximum deposition intensity for the given effective area of the sieve plate. In the present study, the scale down model of Jornada dynamic penetrometer at different locations of the test tank has been employed to quantify the soil resistance and to qualify the uniformity of placement density throughout the sand bed at different height of fall. The study also reveals that sand beds of wide range of relative densities can be achieved at different deposition intensity employing different sieve plates.

The small-strain shear modulus of unsaturated soils is a valuable tool for use in engineering practice, given that most soils remain unsaturated throughout the operational lifetime of the earth structure. Shear modulus is a key parameter required in the response behavior of geotechnical earth structures. Since the measurement of shear modulus for unsaturated soils is extremely time consuming and requires elaborate and expensive testing equipment, it would be beneficial to practicing engineers to have empirical or semi-empirical methods for estimating the small-strain shear modulus for unsaturated soils. This paper presents a method to describe the shear modulus behavior with respect to the stress state variables of matric suction and net mean stress. This method uses a relationship that allows for the potential of a priori generation of shear moduli for unsaturated soils. The relationship was developed for monotonic loading of remolded normally consolidated soils, without stress history hysteresis effects. The shear modulus relationship was further developed using multiple linear regression analyses to correlate the soil material constants to soil index properties that are representatives of the soil structure and material constitution.

Mohr-Coulomb strength is significantly influenced by vertical effective confining pressures. However, traditional Mohr-Coulomb mechanics do not adequately describe soil behavior under low confining pressures. Herein we present results of total stress laboratory testing to investigate the influence of soil fabric and deviance from Mohr-Coulomb strength for an engineered cohesionless silty sand (SM) under low to zero vertical confining pressure environments. Specimens were prepared and tested under drained simple shear, consolidated-drained triaxial, and unconsolidated-undrained triaxial conditions with total stress confining pressures between 0 kPa and 100 kPa. The data show that the internal granular friction increasingly dominates the total shear resistance of the material for confining pressures below 100kPa, and the soil fabric has a greater influence on the shear resistance for a cohesionless soil continuum. Therefore, for confining pressures less than 100kPa, a better representation of the relationship between shear stress and normal stress can be found by curving the failure envelope and rejoining the 33 degree line observed at high pressures (MPa range) at a confining pressure between 50 kPa and 100 kPa.

The granular media (i.e., ballast and sub-ballast) used in ballasted rail tracks undergo large deformations along with particle breakage when subjected to cyclic loads exerted by heavy and fast trains. The deformation and degradation of such granular layers severely affects track geometry and results into increased maintenance costs. The use of artificial inclusions in planar (geogrid, geotextile, and geocomposite) as well as three-dimensional form (geocell) is essential to curtail such costs and improve track stability. A series of cyclic drained triaxial tests were conducted using large-scale prismoidal process simulation apparatus designed and built at the University of Wollongong. Effects of external confining pressure, frequency, and number of load cycles were investigated. The test results showed that large deformation and degradation of ballast was imminent under high frequency cyclic loading. It was also shown that settlement of the ballast and sub-ballast can be reduced significantly employing geocomposites and geocells, respectively. The results revealed the effectiveness of the geocell, when they are used at low confinement and higher frequencies. This paper provides an insight to cyclic behavior of railroad granular substructure and demonstrates the role of confinement induced through the use of artificial inclusions.

The small-strain shear modulus G₀ is a fundamental property in geotechnical problems such as wave propagation, liquefaction, and soil-structure interaction. The stress dependency of G₀ was examined by determining the particle contact force using the suction stress theory for soils under unsaturated conditions. The correlation between G₀ and suction stress characteristic curve (SSCC) was found for soils under a zero-total-stress boundary conditions. Dependencies of G₀ and suction stress on soil moisture are demonstrated to follow the same pattern but differ by a constant scalar. A linear relationship between G₀ and suction stress with a strong correlation to the soil water retention was found. As such, the suction stress theory was verified to be able to represent the particle contact force for unsaturated soils under zero total stress boundary conditions.

Soil moisture and suction are two key variables that often need to be measured for unsaturated soil. They are commonly measured by separate soil moisture and suction sensors which require double installation efforts and often result in questionable correlation between the measured moisture and suction. Attempts were made to combine time domain reflectometry (TDR) and porous blocks functioning as tensiometers and have demonstrated a great potential of the TDR for simultaneous measurements of soil moisture and suction. In this study, a new TDR moisture-suction probe is designed based on the previous study, and it was evaluated in laboratory for simultaneous measurements of moisture content and soil suction. The probe has two parts with one half portion embedded in a dental plaster (i.e. gypsum) for soil suction measurements, whose suction is equilibrated with the surrounding soils. The other half portion of the probe is also inserted into the soils to measure moisture content. The probe calibration was completed by the use of pressure plate tests to establish a relationship between suction (ψ) and measured dielectric constant (K_a) of the gypsum block. Then, it was tested in a silty sand to evaluate its function for soil moisture and suction measurement. The preliminary test results demonstrated that the change of K_a of the gypsum corresponded well to suction level from 10 to 750 kPa, and it can measure moisture content and soil suction accurately for the test soils. The new probe can be fabricated easily and fast, without any additional maintenance and has a great potential for field measurement of soil moisture and suction.

Unbound aggregate pavement base and subbase courses distribute wheel loads to protect subgrade. Appropriate selection of aggregate material is essential to ensure a stable and long lasting pavement. Both aggregate compaction and strength are influenced by the amount and nature of finer materials controlling the gradations of base and subbase. Current standards such as AASHTO and ASTM have suggested control limits on quantity and plasticity of fine contents. Proportion of percent passing No. 200 sieve to percent passing No. 40 sieve is called dust ratio, which defines the quantity of small sizes in a sample. However, many states either waived some of the AASHTO or ASTM criteria on fine contents or developed their own specific control measures for quantity and quality of fines in aggregates. This study has the objective to identify appropriate quantity control measures for inclusion of plastic fines, i.e., plasticity index of approximately 5%, in crushed limestone aggregates in Illinois. The results of standard Proctor type compaction and soaked CBR tests performed on samples after four days of soaking were used to identify the effects of the different dust ratios and percent fines contents on dry unit weight and aggregate strength.

Asphaltic concrete has been used as impervious core in embankment dams because it can be built quickly and efficiently even in areas with high precipitation in contrast to embankment dam with clay or till cores. In this study, a series of resonant column tests were conducted on asphaltic concrete samples to investigate the effects of temperature on dynamic properties for different confining pressures. Samples were tested at the temperatures of 0, 5, 10, 15, and 22°C. Technique used to conduct temperature controlled testing in resonant column test is presented. Resonant column testing at each temperature was performed at three confining pressure of 50, 150, and 350 kPa. Effect of confining pressure variation on dynamic properties of asphaltic concrete samples is negligible. However, shear modulus and shear wave velocity change significantly as a function of temperature; For instance, as the temperature increases from 0 to 22°C, the shear modulus and shear wave velocity decrease approximately 25% and 13%, respectively.

This study reports a laboratory investigation to the permeability of a typical marine sand, i.e., calcareous sand, which is widespread in South China Sea. Through the traditional permeability test, the relationships between flow velocity and hydraulic gradient have been measured for the calcareous sands. To investigate the effect of particle size distribution on the permeability, calcareous sand specimens with varied uniformity coefficients and curvature coefficients have been tested in the tests. A significant permeability dependency on the particle size distribution can be recognized from the test results. In light of the unique properties of the calcareous sands, an investigation to the effect of the particle shape on the permeability was performed by comparing with glass spheres. The result indicates that due to the irregular particle shape, the calcareous sands behave an apparent deviation in the permeability from the glass sphere specimen composed of regular particles.

Use of reinforcement in flexible pavements is gaining its popularity worldwide. Many studies are available in the literature on performance improvement of pavements using high-strength geogrid reinforcement. Various other types of reinforcements have made their way in the market. One such reinforcement type is hexagonal shaped steel-wire-mesh reinforcement with double twisted wires that has shown promising results in resisting rutting and fatigue cracking of flexible pavements. In this study, unpaved pavement structure overlying medium-stiff subgrades is considered. Large-size test chamber of dimensions equal to 1m x 1m x 1m is used to assess the performance of pavement structure under static loading. The load is applied through a 150 mm-diameter plate using a hydraulic actuator. The subgrade soil with a relative density equal to 70% is prepared by controlling the compacted density. A total of five test sections are considered- (a) unreinforced control section, (b) three geogrid-reinforced sections with different d_r/B ratios (equal to 0.3, 0.45, and 0.6), where d_r is the depth of reinforcement and B is the diameter of loading plate, and (c) one steel-wire-mesh reinforced section with reinforcement placed at optimum reinforcement depth ratio, d_r/B. Load improvement factors are proposed to quantify the improvement in the behaviour of reinforced pavement structure over unreinforced pavement structure.

A study was conducted to investigate the feasibility and practicability of using the infrared heating technique for carrying out routine soil moisture content tests. Only 1 out of 1,400 measurements (<0.1 %) showed that the temperature of the soil specimen had exceeded the threshold value of 110°C by 1.5°C for about 5 minutes in the drying process. Two sets of comparative tests subsequently carried out indicated that there was virtually no difference between the infrared method and the conventional method using a convection oven. The moisture content test of the majority of the commonly used fill materials in Hong Kong could be completed within 3.5 hours, which could facilitate the early determination of relative compaction and hence the progress of filling works. The new test was also proven to be efficient, low-cost and environmentally friendly due to less energy consumption and an economical alternative to using the conventional convection oven.

Utilizing rubber tyres in vibration mitigation can be a viable approach of resolving the chronic problems associated with disposal of waste tyres. However, the dynamic properties of sand-tyre crumb mixtures (STCM) are essential for the design of a vibration isolation system. In this study, the dynamic properties of STCM in terms of shear modulus and damping ratio are presented against the shear strain. The modulus and damping ratio of STCM for small to large shear strain were measured using Torsional resonant column tests and cyclic triaxial tests, for two composition of tyre crumbs (50% and 75%) and three different confining pressure (50, 100, and 200 kPa). The results showed that, shear modulus and the damping ratio of the mixtures are strongly influenced by the percentage of rubber inclusion. Shear modulus decreased with an increase in tyre crumb inclusion for all the confining pressure, whereas the damping ratio increases with the increase in rubber content in STCM. For any percentage of tyre crumbs inclusion, the shear modulus increases and damping ratio decrease with increasing confining pressure. These results are useful to understand the dynamic response of STCM and further used in model studies to design a low cost isolation system.

The small-strain shear modulus depends on soil type, void ratio, stress level, and degree of saturation. Models have been proposed to describe G₀ of either saturated or unsaturated soils, yet none of them can predict G₀ for soils under both conditions. In this paper, a unified model for G₀ was proposed for soils based upon the consideration of effects of both material hardening/softening and inter-particle contact forces. These two mechanisms are characterized by degree of saturation and effective stress, respectively, as primary variables. Suction stress theory was used to determine the effective stress for soils under both saturated and unsaturated conditions. It is shown that G₀ is correlated with the soil-water retention curves of unsaturated soils by using the suction stress in the effective stress framework. The proposed model fits well for 17 soils, including those from the literature and newly tested ones under different saturation conditions and various loading conditions. A correlation between the fitting parameters of the proposed model and the inverse of the air-entry suction was found to provide good predictions of the small-strain shear modulus for unsaturated soils under various loading conditions.

B.F. Sisk Dam is a 116.4 meter high zoned embankment structure located near Los Banos, California on the west side of the Central Valley, and is currently the subject of two investigations - one studying potential remedial actions to decrease the risk associated with potential seismic activity in the region, and a second in support of feasibility level designs for increased water storage and embankment crest raise. The impervious core of the embankment is comprised of heavily compacted sandy lean clay. As part of the current investigations, several bore holes were drilled from the crest of the dam and intact samples of the core material were retrieved. A comprehensive laboratory testing program was undertaken including one-dimensional consolidation and K_o-consolidated undrained static triaxial shear testing. This paper presents the details of the testing program, depicts typical results, and discusses the proposed undrained strength definitions for stability modeling. Proposed undrained strength definitions for modeling used an undrained strength ratio for normally consolidated core materials and SHANSEP analysis for overconsolidated core materials. For very shallow embankment materials, the SHANSEP strength approach was modified to reflect lower strengths produced by the effective stress friction angle.

Geopolymers are inorganic polymeric substances, which are synthesised from raw materials rich in silicates and aluminates. When these raw materials activated with alkaline solution, a complex aluminosilicate gel forms due to polymerization process. However, the proportion in which the alkaline solutions used largely controls the geopolymerisation process. Thus, it is essential to understand the influence of alkaline solutions on the behaviour of geopolymers. With this in mind, an attempt was made to study the effect of Na₂SiO₃ to NaOH ratio, NaOH molarity on synthesis of fly ash based geopolymer mortar. Compressive strength and morphological characteristics were established, and the influence of (a) Na₂SiO₃ to NaOH ratio (viz., 1, 1.5, 2, and 2.5), and (b) NaOH molarity (viz., 10M, 12M, 14M, 16M, and 18M) were investigated on these properties. Results show that samples at Na₂SiO₃ to NaOH ratio of 1.5 exhibit maximum compressive strength values. It has been found that the compressive strength increased with increase in NaOH molarity till 16M and thereafter, strength found decreased with further increase in NaOH molarity. Morphological studies using environmental scanning electron microscope (ESEM) on the samples cast with different Na₂SiO₃ to NaOH ratios reveal that hardened mortar samples contain unreacted fly ash particles and the amount of unreacted particles seen increased with increase in Na₂SiO₃ to NaOH ratio.

Soil contamination is a worldwide problem nowadays. Basic properties of soil will be changed after contaminated. Diesel oil and kerosene are typical light non-aqueous phase liquids (LNAPLs), Atterberg Limits, pH, particle size distribution will be changed after contaminated by these oils. In this study, 0# diesel oil (in Chinese standard) and kerosene were used as contaminations, classical Yangtze River back swamp silty clay in Nanjing City was used as the study material, contaminated soils with different oil contents of 0%, 2%, 4%, 6%, 8%, and 10% (ratio of oil weight to soil dry weight) were artificial mixed in the laboratory. Laboratory tests including soil grain size distribution, pH, Atterberg limits were conducted to verify the effect of oils on soil properties. Scanning electron microscope were also done to examine the change of microstructure of soils before and after contaminated. Rules of contaminations effects on the change of soil basic properties were obtained. Results show that different oil contaminated soils have similar change rules. With the increase of oil content, both of clay particle and silt particle increase. Micrograph of scanning electron microscope show that soil small particles increase with the increase of oil content. Both of the two contaminated soil pH, liquid limit, plastic limit and plasticity index decrease all decrease with the increase of oil content.

“Monitored natural attenuation” of chlorinated solvents is presently seen as one of the most technically feasible and economic means to manage remediation of sites contaminated with these compounds. Optical spectroscopic analysis methods offer the fieldability and analytical potential to enable cost-effective long-term monitoring of the attenuation process. However, their value in these settings is often compromised because aqueous media in the hydrogeological environment tend to contain naturally occurring non target fluorophores, which adversely affect the quality of in situ optical spectroscopic measurements. The purpose of this research was to characterize the influence of three different fluorophore emissions on time resolved Raman spectroscopic (TRRS) analysis of aqueous trichloroethylene (TCE) samples. The investigated fluorophores included naturally occurring humic acid (C₉H₉NO₆), and the anthropogenic compounds, fluorescein (C₂₀H₁₂O₈) and rhodamine B (C₂₈H₃₁CIN₂O₃). Key characteristics investigated included the form of the fluorescence spectra, their mean decay times, and the TRRS signal-to-noise ratios (SNR) at varying counting-times achievable in the presence of each fluorophore for both direct monitoring of TCE at the 381 cm^-1 (δ skeletal) Raman line and indirect TCE monitoring via observation of the water (OH stretching) Raman line at 3393 cm^-1. Results indicate that optimal SNR for TRRS measurements of fluorophore doped TCE samples is likely obtained with counting times less than ½ of the fluorescence lifetime of the involved fluorophore.

Oedometer tests were performed on the reconstituted Wenzhou clay with different pore salt concentrations to investigate the influence of salt leaching on the compression behavior. The pore salt concentration of Wenzhou clay was adjusted using different concentrations of NaCl solutions. It is observed that the e-logσ_v’ compression curves of the reconstituted clays with a higher salinity always lie above those with a lower salinity. As the salinity increases, the compression index increases, and the remoulded yield stress decreases. In addition, Burland’s concept of the intrinsic compression line is adopted for correlating the compression curves of the reconstituted clays with different pore salt concentrations. The intrinsic compression parameters of e₁₀₀^* and C_c^* increase with the increase in the pore water salinity.

The application of electromagnetic (EM) waves to measure the electrical properties (dielectric constant and loss tangent) of materials is a well-known approach. The electrical properties can be used to indirectly measure several physical properties of solutions in water such as the concentration and chemical composition of contaminants in water, as a representative of the liquid phase in soil. A capacitive method of measuring dielectric properties of solutions is proposed to detect and determine low-concentration chemical and biological contaminations in water. The primary objective of this project is to design a low-cost sensor that would require small volumes of samples to detect low concentrations of dissolved contaminants in water. A forward model was developed using a finite-element method (FEM) to simulate the experimental setup (EXP). A calibration function was also developed to minimize deviations between FEM and EXP results for benchmark/reference solutions with known dielectric properties. The validated, calibrated forward model was then inverted to calculate the electrical properties of unknown solutions using the corresponding EXP results.

Heavy metals such as lead and cadmium in water present a major environmental and health risk. Conventional methods of heavy metal detection in water involve sampling and subsequent transport to a laboratory for testing. Standard spectroanalytical instruments are expensive, bulky and require trained personnel for operation and cannot be implemented for on-site sensing. There is also the risk of exposure of contaminated media to field workers and laboratory personal. This research describes a novel handheld electronic tongue for qualitative and quantitative analysis of lead and cadmium in water. The electronic tongue consisted of a miniature potentiostat, silver/silver chloride reference electrode, platinum counter electrode, and a glassy carbon working electrode. The potentiostat was programed to perform both square wave and differential pulse anodic stripping voltammetry. Laboratory calibration tests were conducted to identify and measure concentrations of lead and cadmium in samples of water. A pretreatment electrolyte solution was used to increase sensitivity. The resulting data was analyzed using regression tree analysis. The device and methodology developed in this research were capable of detecting lead and cadmium at low parts per billion limits.

Leaching characteristics of recycled asphalt shingles (RAS) mixed with self-cementing fly ash (FA) for use as structural fill materials were investigated. Long-term column leaching tests were conducted on the compacted RAS-FA mixture containing 10% and 20% self-cementing FA. Results showed that peak concentrations for all investigated elements occurred in the first 5 pore volumes of flow (PVFs). Only arsenic (As) and selenium (Se) exceed the maximum contamination levels (MCLs) of U.S. EPA drinking water standard. The peak concentrations of As and Se from RAS-FA (80-20) were 10.2 and 18.8 times higher than the corresponding MCLs (As_MCL = 10 ppb and Se_MCL = 50 ppb), while lower leached As and Se concentrations from the RAS-FA (90-10) were observed (7.1 and 1.8 times higher than the MCL values). WiscLEACH model was used to predict the environmental impact of RAS-FA mixtures as structural fills and calculate the reduction factors (RF) at a point of compliance (POC) 30 m away from the centerline of the roadway. The calculated RFs of As and Se were 14 and 18, respectively, and only concentration of Se leached from RAS-FA (80-20) were predicted higher than MCL at the POC. Based on mechanical and environmental evaluations, RAS-FA (90%-10%) is recommended for highway applications.

Long-term leaching characteristics of chromium ore processing residue (COPR) (≈ 250 pore volumes of flow, PVF) was investigated using laboratory flow-through column testing with synthetic groundwater (GW). Two saturated flow-through column experiments simulated the long-term migration of total [Cr(T)] and hexavalent chromium [Cr(VI)] from two types of COPR [unweathered, gray-black (GB) and weathered, hard-brown (HB)] via advective groundwater flow. The release of Cr(T) and Cr(VI) from GB and HB COPR showed peak concentration before 5.5 PVFs, and decreased significantly thereafter. The long-term concentration of Cr(T) and Cr(VI) from GB COPR after 150 PVFs were found to be 21 ± 4 mg/L and 20 ± 5 mg/L, respectively, while, concentration of Cr(T) and Cr(VI) from HB COPR after 150 PVFs were found to be 25 ± 4 mg/L and 23 ± 3 mg/L, respectively. The GB COPR released 21.3% w/w Cr(T), and the HB released more Cr(T) (32.4% w/w) within the testing period. However, a significant amount (> 65%) of chromium remained in the COPR and will continue releasing for an even longer period. Amorphous compounds may be an important sink related to release of chromium, which can explain the higher release of Cr from HB COPR.

Visualization of internal geotechnical processes in physical modelling is possible through the use of transparent soils. These materials rely on optical clarity hence a systematic impartial user-independent assessment framework for visual quantification is necessary. The visual quantification of transparent soil models have been traditionally done by Snellen eye charts. Black and Take (2015) introduced an independent method called modulation transfer function (MTF) to quantify the visual quality of transparent soil models. This method incorporates optical calibration charts consisting of black and white grids of different spatial frequency (pixel intensity). A new transparent material named Gelita is introduced to model clay and assessed using this standardized framework. Different mixture ratios of transparent Gelita (5% to 20%) are produced and visually tested. Viewing depth is varied from 50 mm to 150 mm and tests are repeated to quantify this effect on the visual transparency of Gelita. It is found that smaller mixture ratios of Gelita have the highest MTF and therefore offer the highest optical quality. The effect of viewing depth is more pronounced in samples of Gelita of larger mixture ratios. Re-use of the material by secondary melting does not significantly affect transparency regardless of the mixture ratio.

Currently the mix fuel from breakdown of underground storage tanks, and rain water are infiltrating into the ground with potentially large geo-environmental impacts. The contaminated soils are changed towards a new equilibrium level so we need knowing its physical and chemical properties and its mechanical behaviour. We used triaxial tests in evaluating the environmental effects of gasoline (BTEX elements) on the shear stress-strain behaviour and on the hydraulic conductivity or permeability coefficient; they are performed with clean and contaminated soil specimens of residual granitic soil. The influence of confining pressure and hydraulic head on hydraulic conductivity were also addressed. The physical and chemical properties and retention mechanisms in contact with contaminants cause spatial rearrangements, consequently, hydraulic conductivity with increasing stress levels is randomly decreasing. This effect manifests itself in smooth increasing shear strength of contaminated soil.

Transparent soils combined with non-invasive imaging techniques allow internal visualization of geotechnical processes. Oil-based transparent silica has been traditionally used for measurements of deformation patterns, soil structure interaction (SSI), flow pattern, and permeability. New water based environmentally friendly transparent material, Gelita, can be used as a transparent soil to model fine grain clay soils. Gelita has been extensively used in applied mechanics as a standard target to test bullets or to simulate human tissue. However, the potential of this material to serve as a soil surrogate and its correlation to basic geotechnical properties have not yet been investigated. Material properties and transparency of Gelita depend on its mixture ratio with water. For example, a 5% by mass Gelita mixture offers high optical transparency; however, it exhibits extremely low strength characteristics. As the mixture ratio (density) of Gelita increases, its transparency is reduced, but it offers a higher strength. This paper investigates the effect of Gelita mixture ratio, confinement, displacement rate and over-consolidation ratio on the resulting shear strength, for the purpose of being used as a soil surrogate for modeling applications.

Bridge abutments constructed using geosynthetic-reinforced soil (GRS) with an integrated bridge system (IBS) are becoming increasingly popular because of cost efficiency and rapid construction. Monitoring the vertical and lateral deformations of the GRS-IBS facing is one technique that has been used to assess performance. The conventional approach is to measure vertical and lateral deformations using a standard survey level and rod. This paper describes lessons learned from the use of three-dimensional (3D) stationary terrestrial laser scanning (TLS) to measure facing displacements for a two lane 32 m long GRS-IBS constructed in Sheffield, MA. The intent was to measure displacement of the split-face segmental concrete block facing by comparing position measurements obtained before and after placement of the bridge deck on the abutments. A simple procedure is followed to analyze the point clouds. The high measurement density and resolution provided by the laser scanner enables detailed observation of how the abutments deform in response to the applied loads. The capability of the proposed procedure to measure displacement is discussed in the context of the displacements allowed in the current GRS-IBS design methodology.

The behavior of buried flexible pipes is one of the complex soil-structure interaction (SSI) problems in geotechnical engineering. Additionally buried pipe system exposed to parallel trench excavation is special design situation and requires careful attention during design in order to avoid unanticipated failures. Present study describes analyses of parallel installation of four numbers of 3,840 mm outer diameter and 20 mm thick buried mild steel pipes to study influence of the parallel trench excavation, hydro test load, unanticipated rainfall and different backfill/bedding properties on the deformation of buried pipes. Staged construction method was adopted in geoslope (Sigma/W) analysis for investigation of the displacement response of pipe. The pipe was modeled as a structural beam element with 5 bar internal operational pressure, hydrostatic water pressure due to ground water and self-weight. The effect of parallel trench excavation on one side of the pipe installation was analyzed and distributions of pipe deflection at each stage were monitored. Additionally, the different pipe bedding properties were considered in order capture the effect of modulus of soil reaction on the pipe displacements. The stresses along the half perimeter of the pipe are compared to differentiate the difference in the surrounding reaction/pressure. The results were discussed and are compared with performance and deformation of the pipes actually installed at site. Study highlights that current design recommendations as per AWWA M11 (2004) or equivalent does not provide sufficient guidance for such special design situations and recommends further research in order to provide sufficient design recommendations which can be practiced confidently.

In-situ geotechnical characterization of weathered limestone in Florida is important because typical drilling operations may not provide sufficient core specimens for testing. Cross-hole ground penetrating radar was used to characterize a sequence of soil overlying weathered limestone bedrock at a geotechnical test site in north central Florida. Zero offset profiling (ZOP) provided radar velocity as a function of depth between boreholes. Multiple offset gather (MOG) data was used to produce a radar velocity tomogram between boreholes. Using published radar velocities as a guide, it was possible to distinguish the stratigraphy in the boreholes. The radar velocity based stratigraphy compared well to information from driller’s logs which were produced during the installation of the cased borings. Using the MOG tomograms, a cavity within the bedrock could clearly be identified. The radar velocities noted within the limestone were less than published results which is due to the highly weathered nature of the limestone at the site. Cross-hole ground penetrating radar can be a valuable tool for geotechnical site characterization.

The horizontal permeability of thinly bedded foundation soils is one of the primary factors that controls the time-rate of consolidation during embankment construction. This paper explores using a tri-element water source housed in a push-in CPT permeameter device to measure the in situ horizontal permeability of thinly bedded sediments. As constant water pressure is applied, horizontal radial flow is achieved in the middle element because its flow is constrained by the parallel flow from the above and below elements. This effect eliminates any tendency for immediate vertical flow from the middle element and allows for direct measurement of the horizontal permeability using the flow equations derived for steady-state radial flow to a fully penetrating well. Although this paper explores the use of this concept for obtaining design properties for time-rate of consolidation calculations for low permeability soils with prefabricated vertical drains, this concept may also be utilized for any thinly bedded sediments where obtaining the true horizontal permeability of the soil is required, such as environmental and ground water assessments.

Due to a few limitations through laboratory testing, CPTu has been realized as a multipurpose apparatus with an acceptable performance especially in coastal deposits. Traditional methods for obtaining shear strength parameters using CPT data, estimate conservative values for ϕ (internal friction angle) in granular soils and S_u (undrained soil shear strength) in cohesive soils. In this study by combining bearing capacity theorem and direct shear modes at CPTu tip and sleeve and considering the pore water pressure at the shoulder of Piezocone (u₂), a set of equations is derived. Hence by input of CPTu data including q_t, f_s and u₂ at a certain depth, soil shear strength parameters i.e. C (cohesion) and ϕ can be calculated simultaneously. Via establishing a data bank, consisting of 38 sets of CPT and CPTu boreholes from marine deposits at various coastal regions, measured soil shear strength parameters are compared with traditional and proposed approach estimations. Although the calculated C and ϕ by proposed method are relatively closed to the measured results and covering all sorts of soils, they can satisfy CPTu measured shear strength collaborating to each other. Moreover, a soil classification chart and a graphical solution with utilizing the proposed method are provided.

As a result of the difficulties in obtaining undisturbed samples in cohessionlesss soils, CPT-based empirical correlations often developed from calibration chamber experiments are widely used for determining many soil parameters for geotechnical investigation. This paper describes the application of 19 reduced-scale calibration chamber cone penetration tests for evaluating empirical correlations for predicting relative density, unit weight, and constrained modulus for loose to medium-dense sands. A 6 mm-diameter subtraction cone with an apex angle of 60^o and a net area ratio of 0.75 is used in the laboratory tests. Cone tip resistance, sleeve friction, and pore pressure at the cone shoulder are measured. No excess pore pressure developed in the CPT experiments on the fine sand. Empirical correlations are suggested for predicting the dry and saturated unit weights of silica sands. Existing empirical correlations display a very wide range of estimates for sand relative density and often very different from the experiments of this study. However, the constrained moduli exhibit a better agreement with an empirical correlation.

Sustainable infrastructure research has led to an increase in the use of stormwater control measures (SCM). Rain gardens are vegetated SCMs which promote infiltration, evapotranspiration, or both. As the use of rain gardens and other sustainable practices becomes more common, cost effective techniques are needed to determine site properties for design and to assess their performance after construction. A major component of rain garden performance is hydraulic conductivity, which can be determined by infiltration testing. The double-ring infiltrometer test, while commonly used in practice, can take long periods of time to complete. Single-ring infiltrometer tests often use less water and are require less time to implement, enabling more tests to be completed in the same period of time. Seven small single ring infiltrometer tests were performed at a rain garden on Villanova’s campus in Fall 2014 to determine the field hydraulic conductivity of surficial soil in the SCM. The instrumentation at the site used in the field study has been recording the recession rate in the pond over the past twelve years. Comparing the pond recession rate to the field hydraulic conductivity, it was found that the less commonly used single-ring infiltrometer method can be an accurate predictor of SCM performance.

Resistivity of soils has been widely used for analyzing both geotechnical and geoenvironmental problems. Mapping the distribution of resistivity provides significant information for site characterization including soil properties and contamination in the subsoil. In this research, the distribution of resistivity of a silty sand is investigated using resistivity piezocone penetration test (RCPTU) based on geostatistics. First, to achieve stationary Gaussian random field, the trend removal and Box-Cox transformation were used to convert non-stationary and non-Gaussian resistivity measurements into weakly stationary normal random field. Then semivariogram was used to describe the spatial variability of the residuals including variance, correlation length and nugget. The maximum likelihood (ML) estimator was applied to estimate the theoretical semivariogram, revealing that anisotropy exists in the spatial correlation structure. Ordinary Kriging was then used to provide the best linear unbiased estimates of residuals at unsampled locations of the random field. Finally, cross-validation, or removing some known observations from the database and predicting the known results, was used to validate the geostatistics model. It was shown that the geostatistics is a powerful tool to map the resistivity of subsoil by considering the spatial variability characteristics.

Deep ground freezing to a depth of about 135 feet, including an approximately 85-foot-thick marine clay layer was utilized at an urban site in the northeast United States for temporary earth support during construction of below-grade structures. Since the freeze pipes were shut off in late 2002, up to approximately 9 feet of ground settlement has occurred, impacting site facilities including railroad tracks and underground utilities. After being retained in 2007, GZA GeoEnvironmental, Inc. (GZA) has utilized an observational method as a key component of study. Various geotechnical instruments have been used to monitor settlement rates up to approximately 1 inch per month. The observational method employed has allowed for a more enlightened remedial design process to occur, avoiding potentially wasteful emergency measures, and leading to a more sustainable rehabilitation of site facilities impacted by the settlement, including a deep 42-inch drain line.

This paper presents findings from a field study conducted on a 5.2 km long roadway section on Route 4 in Kandiyohi County, Minnesota. The study involved mapping the existing granular subbase layer and the overlaid hot-mix asphalt (HMA) non-wearing and wearing course layers with a Sakai double drum intelligent compaction roller integrated with a compaction control value (CCV) measurement system. Comparison of CCV maps for the subbase and HMA layers showed that “soft” and “hard” areas identified on the subbase layer were reflected on the HMA layers. Analysis of the CCV measurements yielded a statistically significant relationship showing that variability observed in HMA layer measurements are strongly influenced by the variability in the subbase layer. During construction, a small section of the HMA non-wearing course layer showed premature cracking under construction traffic. The “failed” area produced low CCV values in both subbase and HMA layers. A review of construction records indicated that the subgrade layers in the “failed” area also experienced significant rutting under test rolling. Results demonstrate the importance of foundation support conditions on the performance of the HMA surface layer and the CCV measurements in the HMA layer are a reflection of the stiffness of the foundation layer.

Constrained soil investigation works bring inevitable uncertainties in estimating the true geotechnical design parameters. This uncertainty leads to misinterpretation of failure analysis which can later cause catastrophic damage to infrastructure. In order to avoid such circumstances, one possible way is to conduct additional in-situ tests. However, increase in in-situ tests results in additional project costs and produces negative environment through carbon emissions. In this research study, an approach is proposed to interpret the subsurface profile using geostatistical theories. The cone penetration test soundings (CPT) obtained from a soil exploration study conducted in Texas, USA was considered for the analysis. First, all the available CPT soundings were used to predict and map the variation of tip resistance, friction ratio and soil behavior type index over entire area using geostatistics. Later, a subset of original CPT soundings was used to predict all the three parameters over entire area. Both the maps produced from geostatistical analysis were compared to ascertain the quality of predictions. The results and analysis depicted that the geostatistics could able to accurately predict the soil properties with only a subset of total CPT soundings. This research highlights the adaptability of geostatistics in predicting the subsurface profile with limited data and its contribution towards the sustainable environment.

In this paper, experimental results are presented from a cohesive embankment construction project on US30 in Iowa, where machine drive power (MDP) based roller-integrated compaction monitoring technology was used. The project involved testing test beds with multiple roller passes and production compaction areas with multiple layers of fill material. Data obtained from in situ testing were used to develop site wide correlations and data obtained from multiple lifts were used for three-dimensional visualization and geostatistical analysis. Spatial visualization of multiple lifts indicated that a “soft” zone with relatively low MDP on the first lift was reflected through four successive lifts of fill material (up to about 1.6 m) with similarly low MDP values in that zone. Geostatistical semi-variogram analysis on MDP measurements on five lifts indicated that the variability reduced and the spatial continuity of the measurements improved from lifts 1 to 5, which indicates “bridging”. Regression analysis results indicated that in situ elastic modulus and California bearing ratio (CBR) measurements are better correlated with MDP than dry density measurements. Multivariate non-linear regression analysis was performed including moisture content to predict MDP from elastic modulus and CBR, which showed slight improvement in the correlation coefficients.

With the aging highway infrastructure, growing demands for usage, and constrained funding for repair and rehabilitation, a reliable and cost-effective monitoring of the highway infrastructure has become more important than ever. As highway infrastructure failure or deterioration in many cases is associated with its substructure and subsurface conditions, this study explores the feasibility of integrating a sensing unit–a radio frequency module–and a miniature accelerometer to monitor the subsurface conditions, such as moisture content and possible movements or motions. The prototype of the sensing unit was evaluated through a laboratory flume test that simulates flowslide in a box with a length of 91.4 cm (3 ft), a width of 30.5 cm (1 ft), and height 30.5 cm (1 ft). Two wireless sensing nodes were embedded in the midheight of the soil while other wired accelerometer and piezometers were also installed. Measurements of received signal strength from the radio module on the sensing node revealed the change of water content or water intrusion in the soil. It was also found that the sensing node was able to remotely detect the water content change in comparing to the point measurements from the piezometers. Measurements from the wired accelerometer coincide with pore water pressure measurements and captured the initiation of the flowslide.

This study suggests a practical method for estimating site-specific strain dependent shear modulus and damping. The method uses in-situ shear wave velocity measurements and commercial cyclic laboratory tests on higher strains (i.e., 0.5% to 1%) in which the effect of disturbance is less significant. Shear modulus calculated using in-situ shear wave velocity and at higher cyclic shear strain, is used for building a hyperbolic relationship for shear stress and strain. Modified Masing’s rule and the experimental hysteretic damping at that higher strain are used to create strain dependent damping relationship. As a result, the effects of sample disturbance on lab test results are reduced, and the number of laboratory tests decreases significantly.

Although Perzyna’s theory of viscoplasticity has been accepted and used widely, there is no proper and unified method to determine this model’s parameters for granular materials such as sand under high strain rate conditions. To study these parameters, both static and dynamic tests have been conducted on Ottawa sand. The method used to determine the physical behavior of sand at high strain rates was the split Hopkinson pressure bar (SHPB) method. Experimental stress-strain results from granular soils ranging from strain rates of 200 s^-1 to 2100 s^-1 are presented in this paper. The constitutive equations are calibrated against the experimental data using the Marquardt-Levenberg nonlinear optimization algorithm.

This paper presents a modified particle generation method, named as the grid method (GM), capable of generating homogeneous specimens for model scale centrifuge studies using the discrete element method (DEM). The DEM specimens were temporarily are divided into grids so that soil particles could be created in batches into a smaller area. Using the specimen, a 2D DEM-centrifuge model was prepared by applying an increased gravity condition, which was then used to study the monotonic loading behaviour of a rigid monopile. This formed the DEM-centrifuge model, and it was found that the GM was efficient in preparing the dense samples because it reduced the overall sample preparation time and managed to generate more homogeneous specimens.

The effect of in-situ variability of undrained shear strength of clay and different soil structure interaction (SSI) modeling approaches on the seismic response of piled-raft supported structure is studied. SSI leads to increased or decreased responses of structure as compared to fixed base design philosophy. The distribution of forces in column and pile head may also depend on inherent variability of soil. This results in an unsafe or conservative design of column and pile due to seismic loading. The soil-piled raft-structure interaction is modeled as beam on non-linear Winkler foundation. Response statistics of the system are estimated using Monte Carlo simulation. Finally, design implications are suggested for seismic design of piled raft supported structure with an emphasis on probabilistic SSI based sustainable design approach.

In this paper, a procedure for updating the spatially varied soil property of drilled shafts using Bayesian theorem is presented. The focus herein is to update the blow count of standard penetration test (SPT-N) using the observed ultimate resistance of drilled shafts in the field. The spatial variability of SPT-N in terms of scale of fluctuation is interpreted with the SPT-N profile obtained from prior site investigation. The updated SPT-N is expressed as posterior distribution, which is a function of the observed ultimate resistance and the prior SPT-N data. The Markov-chain-Monte-Carlo (MCMC) simulation-based sampling method is adopted to generate the posterior distributions of SPT-N. In this process, the correlation of the spatial averages of SPT-N values for estimating shaft resistance and toe bearing resistance is explicitly modeled and updated using field observations. This Bayesian updating procedure is illustrated through a case study of drilled shafts.

Internal erosion has been reported to account for about 50% of the dam and levee failures throughout the world. This paper presents a coupled computational fluid dynamics and discrete element method (CFD-DEM) approach to model piping erosion process in sandy soils. The soil-flow interactions are explained by exchanging the momentum exchange between the two phases. Specifically, flow forces such as buoyant force, drag force and viscous force are considered. The various stages of piping erosion including initial movement, progressive heave and total heave are captured. The required hydraulic gradients to activate the stages are found to be greater than the critical gradient determined by Terzarghi’s theory. In addition, the required hydraulic gradients also change with soil properties including specific gravity and particle size distribution.

In our previous study, pier streamlining was demonstrated to help reduce local scour tendency based on the excess shear stress theory, and thus can potentially serve as an alternative scour countermeasure. However, the Reynolds-averaged Navier-Stokes (RANS) numerical method we previously employed inherently fails to capture the coherent dynamics of turbulence around pier, which also plays an important role in scour mechanism. To address the limitation, this paper employs the detached eddy simulation (DES) method to simulate the flow physics around piers with different extents of streamlining efforts. A total of four test cases were simulated in this study. Systematical comparison of the simulation results among different cases reveals significant variation of the flow physics with different extent of pier streamlining effort in terms of coherent structure dynamics, turbulence statistics, and bed shear stress distribution. Distribution and fluctuation of the pressure acting on channel bed, as well as its indication to scour extent, are also discussed. Findings in this study confirm that pier streamlining helps reduce the local turbulence intensity and therefore can serve as a scour countermeasure alternative.

In this paper, a fluid-solid interaction model has been built by coupling two numerical methods, computational fluid dynamics (CFD) and discrete element method (DEM). By solving locally averaged Navier-Stokes equation for fluid phase and Newton’s Laws of Motion for particle phase, the meso-scale behaviors of fluid-solid systems can be well captured in this model. The coupled model has been verified by two simple experiments: free settling of a single particle and sandpile formation in water. The results show this coupled model explains both particle phase and fluid phase accurately. To get a further understanding of soil erosion in laminar and turbulent flows, a k – ε turbulent model has been implemented into the fluid phase. Comparison between laminar and turbulent models indicates that soil erosion rate can be five times faster in turbulent conditions. Further accurate experimental verifications are still needed considering the complicated interaction forces between fluid and particles and among clay minerals. This framework shows the ability to help to understand soil erosion mechanism for clay and sand in both laminar and turbulent flows.

Scour around bridges and other structures is a major problem in the United States. The available scour prediction equations common in practice have the tendency to over predict the ultimate scour hole depth for design river flows by up to 6 times observed depths. Although these estimates are safe for design purposes, they result in expensive foundation designs if scour hole depth is a limiting design criteria for pile embedment length. In this study four specific scour prediction equations were examined: the HEC-18, the equation suggested by the Florida Department of Transportation (FDOT), the equation developed by Texas A&M University (TAMU), and the Froehlich prediction equations. The performance with regard to flow and sediment conditions that yield the most accurate scour depth predictions was tested for each of these equations. In each case, the prediction accuracy increased significantly for specific site conditions. For example, the HEC-18 equation yielded overall coefficients of determination of R²= 0.61, but improved to R²=0.81 when 0.5 mm < D₅₀ < 5 mm. The presented results may provide future design guidelines by providing suitable ranges of applicability for different scour models under different environments.

Based on the API650 Standard, there are four types of raft foundations for liquefied hydrocarbons storage tanks. Since soil is the only material used in constructing foundation types B.4.1 and B.4.3, we can advance the process through further research to identify their behavior and technical/engineering characteristics. Because settlement is a fundamental problem in foundation design, studying its affecting parameters and estimation approaches are quite important. A study was conducted in South Pars region (Iran) focusing on type B.4.3 foundation, and its settlements were predicted after performing hydro-tests. The general soil profile of the foundation bed was also recorded through some boreholes and crosshole test and some laboratory tests. For settlement estimations on granular soils, we used Schmertmann equation which is a function of the strain influence factor; the values proposed by some researchers for this factor yield conservative values for the settlement of the above storage tanks. In this research, Schmertmann equation was rewritten with the proposed strain influence factor (a function of shear wave velocity) and the amount of settlements of the storage tanks were estimated. Results indicate that, compared with relations presented by other researchers, the proposed relation estimates settlements with highly acceptable precision.

Soil has been used for millennia as a structural material due to its widespread availability, cost, ease of construction, and utility in creating durable, comfortable structures. Modern engineers are reexamining this material in part for the practicality and economy, especially in developing regions of the world; however, it has also attracted interest due to its sustainability. The material has low embodied energy and high thermal mass, and can often be sourced locally. Less attention has been paid to these materials structurally, though, compared to steel and concrete. In this paper, we create a finite element analysis of an earthen structural wall under shear loading. The earthen material behavior is fit to a complex plasticity model for geomaterials that incorporates a smooth tensile-shear failure surface, kinematic hardening, and other features. Localized failure is measured by a loss of ellipticity condition, and post-failure softening modeled with an enhanced strain finite element. These elements include additional internal degrees of freedom to track opening and shear displacement on a surface inserted at the most critical orientation when the failure is detected. The model is used to capture the failure response of structures. In particular, the effect of the weak interfaces is examined.

The presented study is primarily motivated by observations of significant sulfate induced heaving in cement stabilized soils that have occurred in a number of recent construction projects in Ohio. It is well known that the reaction between the sulfate and alumina in soils and calcium of a lime or cement stabilizer often leads to the formation of ettringite, an expansive sulfate mineral that may contribute to the expansion. This subject has been extensively researched in the past but most of the studies have been focused on the experimental aspects. This paper presents a chemo-mechanical approach to better understand the expansive behavior of stabilized sulfate bearing soils. Numerical simulations are performed in the present study to explore different scenarios characterized by distinct predominant mechanisms. The interplay between different mechanisms is examined in numerical simulations based on recently reported experimental results. The simulation results show that ettringite formation and osmosis swelling can play comparable roles in the heaving process. The kinetics of osmosis is also explored in two distinct theoretical frameworks and the modelling results are consistent with the experimental observations.

The freezing and thawing process of soils in cold regions can cause serious damage to transportation infrastructure. This paper provides a microstructure based random finite element simulation model that describes the thermal-hydro-mechanical behaviors of frozen soils subjected to the freezing/thawing process. The mechanical and thermal behaviors simulated by the FEM model agree well with the experimental measurements, which provides a reliable simulation tool to predict the frozen soil behaviors during the freezing and thawing process.

Crushing and grinding are primary contributors to a high energy demand in the mining industry, yet, both are surprisingly inefficient processes, often with efficiencies as low as 1%. We analyze size reductions during crushing and grinding operations and explore the potential of multiplying internal weaknesses in rock materials by non-mechanical means. In particular, when rock blocks (wet or even dry if polycrystalline) are exposed to microwaves, internal cracks can develop along grain boundaries via differential thermal expansion between grains and volumetric thermal expansion of water in pores. Brazilian tests conducted on granite and cement mortar specimens show that the tensile strength decreases proportional to the duration of microwave treatment. Thermal changes, excessive fluid pressure buildup and induced stresses are analyzed in the context of hydro-thermo-mechanically coupled processes. Results confirm that both differential thermal expansion of mineral grains and volumetric thermal expansion of water can generate cracks upon microwave exposure. Optimal conditions are suggested to lower the combined consumption of electric and mechanical energy.

Railways offer an efficient and economic transport mode in many parts of the developed countries including Australia, China and USA. Ballast layer is designed as a load bearing layer for rail tracks and to be free draining, but when the ballast voids are wholly or partially impeded due to the intrusion of fine particles, the ballast can be considered to be fouled. Fouling causes a reduction in the drainage capacity of ballast, thereby reducing the track resiliency and triggering high maintenance costs. Geosynthetics are commonly used in railway construction for reinforcement and stabilization purposes. When railway ballast becomes fouled the beneficial effect of the geosynthetics could decrease significantly. This paper presents a study of how the interface behavior of geosynthetics-ballast copes with fouling using discrete element modelling (DEM) of large-scale direct shear tests. A series of large-scale direct shear tests for coal fouled ballast were carried out in the laboratory and were then simulated in the DEM. Shear stress-strain and volumetric dilation responses obtained from the DEM simulations were in reasonable agreement with those measured experimentally. The contact force distributions of fresh and fouled ballast were captured and shown that the fouled ballast exhibited higher number of contact forces compared to the fresh ballast assembly. This is due to coal fines accumulated in voids among large particles then partially carry and transmit contact forces across the assembly. Strains developed horizontally across the geogrid were also analyzed in this study.