IFCEE 2021: Geoenvironmental Engineering, Geomaterial Modeling, Transportation Geotechnics, and Case Histories

The optimization of all construction processes rests on the exact recording of data. But until recently, especially in Germany as well as in other places around the world, work processes in special foundation engineering were roughly jotted down by hand. Until now, a reliable and well-founded determination of detailed key performance indicators was only possible with a great deal of effort. If, for example, process times were to be recorded on a bored pile construction site, an additional employee was needed since the operator of the device, in addition to operating his highly complex machine, had no way of documenting his work steps with sufficient accuracy. Today’s special foundation engineering machines allow data to be comprehensively recorded and sent to servers. The article provides an introduction to a system that, on the one hand, enables any construction processes whatsoever to be documented and, on the other hand, reduces the need for manual entries on the part of the machine operator to an absolute minimum. The new concept intelligently couples the machine with a cloud in real time using the latest IT in order to guarantee access to the current data inventory of the equipment at all times. Using the method presented in the article, the machine’s current process is determined on the basis of these data, whereby missing data are requested for manual entry via an alternative communication channel. In order to effectively manage highly dynamic process changes on a typical special foundation site, algorithms and approaches from theoretical computer science have been implemented, which enable dynamic adaptation to such process modifications. In this way, the operating status for suitable processes can be automatically determined under ideal conditions and the data is recorded in full. The concept also involves the realization of cooperative work between operator and (special foundation engineering) machines, enabling interaction between operator and machine, and thus minimizing the effort needed for documentation purposes. The key performance indicators are thus based on measured values (sensor data from special foundation engineering machines). As part of the article, the results and findings from construction site operations are presented and optimization cases are explained.

Ground penetrating radar (GPR) is a nondestructive ground survey method that can be used in assessing pavements, bridges, tunnels, and reinforced concrete structures by transmitting electromagnetic waves through the target. In many cases, the use of GPR is especially limited in clayey soil due to the low penetration depth of the radar wave. The penetration depth of GPR is determined by antenna frequency and the electrical conductivity of the earthen materials being profiled. For this study, a GSSI SIR 3000 was paired with a 400 MHz antenna to investigate a failed area within the pavement. The penetration depth was about 6–9 ft in the dry Yazoo clay. At the intersection of W. Pearl St. and S. Farish St. in Jackson, Mississippi, a large sinkhole was formed potentially, due to a leak in a water main. The current study investigated the overall distribution of the sinkhole and identify the potential cause or contributing factors at the W. Pearl St. and S. Farish St. intersection using GPR. The study was performed using a total of 71 2D GPR subsurface profiles, which were considered in two separate tests. The 2D subsurface imaging results were extensively analyzed in the post-processing software RADAN 7 to analyze potentially vulnerable locations. The 2D profiles along each intersecting line, for the two test areas, are analyzed and subsequently combined to develop a 3D profile of the area. Based on the GPR testing results, the extent of the failed area along with the moisture variations within the soil is investigated.

Rainfall-induced slope failure is a common problem in areas with slopes constructed on high plasticity clay soil. Slope failures are frequent in highway embankments and levees on expansive Yazoo clay in Mississippi, which causes significant maintenance problems and requires millions of state and federal dollars to fix it. During the rainfall, water infiltrates through the slope, which saturates the slope and may reduce the matric suction of the soil. However, very limited studies have investigated the variation of moisture and matric suction variation at the field scale. The objective of the current study is to evaluate the performance of a highway slope made of Yazoo clay using field instrumentation. The slope located along Terry Road at the Interstate 20 Interchange in the southwest of Jackson, Mississippi, is considered as the reference slope. The site was investigated using CPT testing and test borings. Moisture and water potential sensors were installed at the crest and middle of the slope at 1.5 m (5 ft), 3 m (10 ft), and 5 m (15 ft) depth. Moreover, two slope inclinometers were installed in the middle of the slope to monitor if there is any potential movement due to the moisture variation. Based on the field monitoring data, volumetric moisture content variation ranged from 20% to 40%, with higher moisture content correlating with rainfall events. As moisture content increased, the matric suction of the slope reached its minimum value at a total of 2-in. rainfall. Due to the change in moisture variation, a 11.43 cm (4.5-in.) movement was observed from slope inclinometer data.

Performance and maintenance of infrastructure located in the vicinity of rock cuts and/or slopes depend on the stability of slopes. Assessing the stability of such rock slopes is essential to ensure the typical performance of such infrastructure. Although three-dimensional (3D) analysis of slopes has shown promising results in assessing complex geometries and boundary conditions, the widespread use of such analysis is hindered by the limited accessibility to 3D data collection and analysis tools. Therefore, this study focuses on using both two-dimensional (2D) and 3D equilibrium stability analyses for evaluating a rock slope geometry. Close range photogrammetry, accomplished by using an unmanned aerial vehicle (UAV) platform, was used to inspect a complex terrain comprising of a rail line passing through a rock-cut. Highly weathered rock mass with low intact strength was considered as a single continuum that undergoes circular failure and analyzed using Spencer’s 2D and 3D limit equilibrium method (LEM). These stability analysis methods were used in tandem to identify the 2D critical sections within the 3D critical slip surface of the rock slope that may need rehabilitation. The results of the study highlight that unmanned aerial vehicles offer a safe and cost-effective solution to collect the 3D data of large slopes located in remote and inaccessible areas compared to traditional data collection methods.

Over the last 50 years, full extraction longwall mining has become an efficient and safer means to remove coal from underground deposits. When enough coal is extracted, a subsidence basin forms on the surface, which causes the ground to drop and induces strains and deformations on the surface. In the winter of 2019, a longwall panel that averaged a depth of 675-ft undermined a section of Interstate 70 (I-70) in Pennsylvania, causing as much as 5-ft of vertical subsidence. As the highway was undermined, the pavement, slopes, and embankments were monitored for signs of failure using regular surveys, instruments, and observations.

Controlled modulus column (CMC) rigid inclusions (RIs) were used to support a new double-sided mechanically stabilized earth (MSE) wall embankment installed as part of a design-build project to replace a viaduct spanning over soft soils along a 1,900-foot-long section of I-690 in Syracuse, New York. The MSE walls were up to 21 feet high and subsurface conditions included loose urban fill overlying intermittent peat and up to 27 feet of soft silt and clay, underlain by bedrock. The project was completed in two phases with partial road closures to mitigate traffic impacts during construction. The first phase included the north wall and roadway with a temporary wire wall on the south side, and the second phase included the south side of the roadway and the south wall. RIs were used to support the MSE walls and the new embankment, and the size and spacing of the elements were optimized for the varying wall heights and soil conditions. The stresses and deformations in the embankments at critical sections were evaluated using 3D finite element models, and various spacings were evaluated using axisymmetric finite element models. Based on the results of the 3D finite element models and stability models, RIs near the MSE wall face were reinforced to resist large bending moments, and high strength geotextile was installed for added resistance to sliding. An added design challenge was the presence of existing piles from the viaduct, which could not be removed and had to be considered in design of the RIs. The embankments were instrumented extensively with inclinometers, extensometers, earth pressure cells, piezometers, and strain gauges in several of the RIs. Instruments were monitored both during and for a period after construction was complete. Instrumentation data were used to check performance relative to project thresholds. Predicted settlement and lateral movement compared well with measured values, and the earth pressure cells and strain gauges showed load transferring into the rigid inclusions over time.

This paper presents the technical design challenges encountered due to the condition and historic nature of a 140-year-old bulkhead and will present issues encountered during construction due to the subsurface conditions and marine environment. Observations of the bulkhead during inspections performed between 1980 and 2014 revealed that the alignment was distorted significantly and had settled. The geotechnical investigation revealed that a soft, weak organic silty clay stratum lies on top of a downward sloping hard glacial sand layer. A review of the historic bulkhead construction records, previous bulkhead investigation reports, subsurface conditions, and results of wall stability analyses revealed that the wall movements were likely caused by a down-slope creep of an inadequate foundation on a sloping hard bottom and the use of newly developed construction techniques in a challenging marine environment. Sonically drilled tiebacks and vertical steel pipe piles drilled through the bulkhead and into the glacial deposit were installed to provide the supplemental lateral restraining force needed to stabilize the bulkhead. A carefully designed procedure of pile and tieback installation sequence and the use of innovative construction techniques were successfully implemented to stabilize the bulkhead.

The project consists of design and construction of a six-story multi-family and senior housing development along the waterfront of the City of San Francisco. The project site was once located at the fringe of the San Francisco Bay prior to the construction of the seawall in the 1860s. Subsequently, man-made fill was placed behind the seawall to create the current waterfront. San Francisco is in one of the most seismically active areas in the world with various active faults within 30 miles in proximity of the San Francisco Bay Region. The North San Andreas and Hayward-Rodgers Creek faults are within 10 mi of the City of San Francisco both capable of generating earthquakes of moment magnitude (M) greater than 7.0. The general subsurface conditions of the site consist of a 20- to 40 feet-thick layer of highly variable artificial fill, which is susceptible to liquefaction based on the geotechnical investigations; the fill also contains considerable amounts of construction debris. Underneath the liquefiable fill, a highly compressible soft clay deposit locally known as young Bay mud (YBM) varies in thicknesses from 5 to 50 ft. Within portions of the site, alluvial deposit was encountered in soil borings underneath the YBM layer. YBM and/or alluvial deposits are underlain by Franciscan bedrock formation at depths ranging from 50 to 80 ft below the ground surface. The Franciscan formation is a complex metamorphosed and deformed bedrock within the subduction zone of western coast of North America primarily consisting of greywacke sandstone, shale, and metashale rocks. The top of the bedrock slopes steeply from one end of the jobsite to another within a horizontal distance of less than 200 ft. This paper will provide a case study of the project summarizing the design and construction of displacement auger cast piles extending into the complex Franciscan bedrock. The challenges include steeply sloped bedrock, soil with very low capacities, high downdrag loads, high static and seismic structural loading demand, sensitive adjacent historic buildings, and site logistics and access. The early involvement of a design-build foundation contractor to select the appropriate foundation type with close collaboration with the owners’ engineers and General Contractor was the key to the success and on-time delivery of the project.

John F. Kennedy (JFK) Airport in New York City is experiencing modification and expansion to meet the increased traveling demand. New terminals are being built supported on piles. The soil formation at the site generally consists of sandy fill, followed by a 5-ft thick organic soft layer. Below the organic layer, deep deposits of glacial sand exist with increased density with depth. Tapertube pipe piles are very efficient in this type of soil conditions. The piles achieve capacity through skin friction along the tapered section. The Nordlund method is generally used to estimate static axial capacity of the tapertube pile. This paper discusses the different analytical methods to predict pile axial capacity and presents assumptions using the Nordlund method for tapered piles that were designed for the expansion of the American Airlines Terminal 8 at JFK Airport. The piles consisted of an 8-in. tip diameter and 14-in. butt diameter with a 15 ft long tapered section plus extension. The paper includes the pile driving analyzer (PDA) results, discussing both CASE and CAPWAP methods. A static load test was also performed, and the results are compared with the PDA results. Lessons learned from this project are shared to help the engineering community with future design and construction of similar projects.

The bi-directional static load test (BDSLT) has become a widely accepted and popular test method for deep foundation elements, such as drilled shafts, ACIP piles, and barrettes. The assembly, installation, and testing of BDSLT foundation elements and interpretation of the resulting data are both an art and a science. Irretrievably installing a hydraulic loading apparatus and instrumentation deep into concrete in a manner that ensures that everything will work correctly takes planning and experience. Once successfully installed, the inverted nature of the test itself requires that the data be properly interpreted in order to be useful for the client, engineer, and ultimately the owner. This paper discusses some of the issues which can arise during the assembly, testing, and interpretation of BDSLTs to the detriment of the project. The various observations have been collected from the author’s extensive experience in the BDSLT field as well as published results in the literature.

Pressure grouting is among the ground improvement methods, which is used to remediate the problematic subsurface geological conditions associated with karst environment and sinkhole activities in Florida. A typical subsurface remediation program may include some combination of shallow chemical grouting, deep pressure grouting, or application of deep foundation (minipiles, micropiles, or full size piles). There are professionals who believe no matter how severe the condition, deep pressure grouting is capable of remediating the problematic subsurface geological conditions associated with karst environment/sinkhole activities and provides reliable and dependable effective compaction of the subsurface soils. Deep pressure grouting on its own may not be the most effective, reliable, and dependable remedial measure for all scenarios. Case histories of unsuccessful remediation of sinkhole related subsurface conditions using deep pressure grouting for residential structures are presented. Failures will be discussed using in situ test data related to subsurface conditions before and after implementation of the remediation program. There are scenarios in which application of some form of deep foundation is required, whether due to severity of sinkhole activity (i.e., securing the structure) or due to value engineering (i.e., optimum engineering and construction effectiveness). An introduction about sinkhole activity in Florida’s geological strata and sinkhole investigation for residential properties in Florida are also presented.

Regional three-dimensional (3D) forward modeling stability analyses are presented for the Egkremnoi coastline of Lefkada Island in Greece. The pre-earthquake 5-m resolution DEM of the region was used as input for the regional 3D model and the modeling results were evaluated for five large landslides that occurred in the area during a M_w 6.5 earthquake that occurred in 2015. The area ratio and the overlap area ratio were defined to quantitatively assess the geospatial “match” between predicted and mapped landslides. Parametric analyses using variable material strength and DEM resolution were subsequently conducted to assess the influence of the input on the estimates of factor of safety, geometry, and location for the predicted most critical landslide. For the cases studied here, the assumed material strength has a greater influence on the factor of safety compared with DEM resolution. However, we find that the DEM resolution has a more pronounced influence on the location and size of predicted landslides.

Deep foundation elements come in many different forms, including driven piles, drilled shafts, and augered cast-in-place (ACIP) piles/continuous flight auger (CFA) piles. Each of these foundation types requires different testing methods to ensure that the particular element has satisfied the design intent. Various quality control tools exist to evaluate the load-bearing capacity and structural integrity of these various elements. As loads on the individual foundation elements increase, there is typically less redundancy, and therefore, a higher risk to the project and owner. Each pile becomes more critical that it performs correctly. Assuring that the foundation has been installed as intended becomes critical. There are many new advances in quality control test methods to evaluate if the installed foundation will meet the design intent. These advances offer innovative, powerful, and cost-effective solutions to deep foundation projects. The way quality control methods are deployed varies in different parts of the world. This paper addresses the current state-of-practice for deep foundation quality control methods and compares how these methods are being deployed in Europe versus North America.

Every year in the USA, dedicated tracked base pile installation rigs, drilling rigs, and cranes tip over or experience near misses due to issues involving inadequate working platforms. These preventable incidents often involve serious injuries or fatalities to operators and ground crews and extensive damage to equipment. Despite the importance of safe, stable working platforms and the dire consequences that can result in their absence, there are currently no specific guidelines or regulations in the U.S. for the design, construction, and ongoing maintenance of safe working platforms. Exacerbating the issue, due to increasing demand for bigger structures that require more intricate, deeper, and larger-diameter foundations, deep foundation construction equipment has become larger, heavier, and more complex in order to deliver challenging requirements. For similar reasons to those behind establishment of guidelines for working platforms in the U.K., an industry-wide Working Platform Working Group (WPWG) was established in 2015, including ADSC-IAFD and PDCA, in order to facilitate industry discussion on improving and standardizing design and construction practices to ensure safe working platforms for all tracked plant and equipment used to install deep foundations across the United States. This paper will discuss best practices with respect to design, installation, and maintenance of working platforms elsewhere in the world and how these practices might best be adapted to the piling industry in the USA. We hope that this is considered to be a major step towards implementing a safe approach to providing working platforms for tracked plant across the USA.

Foamed glass aggregate (FGA) is a lightweight fill material made from recycled glass. In U.S. practice, a method specification is typically used to achieve suitable volumetric stability of the compacted fill without excessively crushing FGA particles. A suite of eight field-scale tests was performed to answer the following questions: (1) what reduction in FGA fill volume is expected using a typical method compaction specification; and (2) what additional volume reduction is expected for additional passes of the compaction equipment beyond what is required by the specification. During the tests, compaction was performed using a dozer (two tests), two track-mounted excavators (three tests), a vibratory plate compactor (two tests), and a small tandem roller (one test) as compactors. Each test involved compacting one to three lifts with multiple passes of the equipment and observing reduction of the fill volume using a lidar scanner. The results show that a typical method specification results in compacted lifts of fill with a volume that is 7.6%–16.6% lower compared to the volume after placement of the lift. Additionally, the results show that the volume reduction follows a hyperbolic relationship with the number of compactor passes, suggesting asymptotic behavior with respect to volume with an increasing number of passes.

Water balance cover or evapotranspiration (ET) cover is an emerging landfill cover system for waste containment. ET cover follows the water store-release principles, and it works with the natural processes to create a better performing landfill cover compared to the performance of a conventional cover. In this type of cover system, evapotranspiration (ET) is the basic mode of water release from the cover to the environment. Hence, ET is the most significant water balance component for optimal cover performance. Among the various water balance components, direct measurement of ET has probably been the most difficult. In this study, ET was measured through the water balance method from six constructed drainage lysimeters having dimensions of 12 × 12 × 1.2 m. The lysimeters were constructed with local fine-grained soil and different native vegetation. All the lysimeters were equipped with instrumentation to have direct measurement of the water balance components except ET. Prediction of ET was also made based on models relying on meteorological information (e.g., temperature, solar radiation, relative humidity). The FAO-56 Penman-Monteith model and modified Thornthwaite model were used in predicting the potential evapotranspiration (PET). Based on the comparison of field measured actual ET through water balance measurement and model prediction, approximately 330–570 mm/year of ET deficit was observed. Different vegetation with varying root zone depth was found to have significant influence on the ET rate for the lysimeters.

Coal mine drainage (CMD) is a by-product of the mining operation produced when coal refuse comes in contact with water. CMD could be highly acidic, containing toxic metals, and hence must be remediated to be discharged in the environment. The traditional CMD treatment methods are expensive, requiring a constant supply of virgin materials such as lime, dolomite, and limestone. In this study, an effort was made to implement sustainable, low-cost alkaline waste materials in treating CMD. Two waste materials, recycled concrete aggregates (RCA) and excess limestone quarry fines (LQF), were used as the treatment materials for CMD. The CMD was generated by leaching of sub-bituminous coal refuses collected from Iowa. Sequential column leach tests were performed, and the remediation efficacies of the waste materials were evaluated based on pH, electrical conductivity (EC), and the CMD concentrations of arsenic (As), chromium (Cr), copper (Cu), and lead (Pb). In addition, the treated CMD was percolated through a soil column to evaluate the potential for groundwater contamination. Results indicated that RCA and LQF could be used for an initial treatment of CMD. The pH of CMD increased, whereas EC and some metal concentrations decreased in the remediation process. RCA showed higher remediation efficacies compared to LQF. In addition, percolation of treated CMD through a soil column further decreased effluent metal concentrations, reducing the risks to groundwater contamination.

The superior toughness and mechanical strength of hydrogel bring much attention to improve the ductility and dynamic loading resistance of geo-materials. The goal of this study was to apply Ca-alginate hydrogel, which is an ironic gelation hydrogel to improve the ductility and mechanical behavior of sandy soil. In this study, the Ca-alginate hydrogel was selected due to its environmentally friendly properties. Up to 0.4% (by weight) of hydrogel was used to mix with sandy materials for their mechanical behavior and ductility improvement. The effects of reaction time, sodium alginate content, and curing temperature on mechanical behaviors of hydrogel-treated sand were studied through unconfined compression tests and scanning electron microscopy. Time is an important treatment consideration. The optimum reaction time was found to be 3 days, and the UCS of Ca-alginate treated sand could achieve 260 kPa in wet condition. The UCS tended to increase with the increase of sodium alginate content, but hydraulic conductivity decreased with the increase of sodium alginate content. The UCS of 0.4% hydrogel-treated sand can reach 430 kPa.

The overall goal of this study is to reveal the microscopic phenomena governing fabric impacts on the shear strength and stiffness of clays using two-dimensional (2D) discrete element models (DEM). Experimental evidence suggests that clay fabric (i.e., the arrangements of particles and void spaces) impacts the clay shear strength. Under a given effective stress, normally consolidated clays with dispersed fabric have higher shear strengths and stiffnesses than those with flocculated fabrics. The 2D DEM models reported here consider the short- and long-range interparticle forces between clay particles that are modeled as rigid rods with a uniform thickness but different sizes. The model was first validated against a laboratory test on a kaolinite clay. Once validated, a series of numerical models were performed to determine the effect of the specimen fabric on the strength and stiffness. The degree of fabric anisotropy was inferred using the distribution of particle orientations. An assessment of the clay microstructure suggested that a stronger Van der Waals attraction exists in dispersed fabrics, possibly being responsible for the higher strength and stiffness of these dispersed fabrics.

This paper presents a numerical modeling to simulate the response of the experimental model studies conducted on bamboo geogrid reinforced fly ash walls under applied uniform load. Fly ash is a nonplastic and cohesionless material that has been considered as a waste, and it is a major concern for countries like India related to shortage of land for its disposal. In this regard, an attempt has been made for proper utilization of fly ash in a massive amount in the field of geotechnical engineering. The present study proposes fly ash as an alternative material to conventional soils to retaining wall applications as a backfill, and bamboo geogrid as a reinforcement. A series of experiments on reinforced fly ash model walls that comprise bamboo geogrid as a reinforcement under applied uniform loads has been conducted. The deformation behavior of the reinforced fly ash walls was studied systematically by considering a vertical spacing and varying the reinforcement length from 0.35 to 0.85 times the height of the model wall (H). The bamboo geogrids were placed in the testing tank in five layers in the form of bamboo geogrid strips. It was observed that the inclusion of bamboo geogrid strips improved the overall performance of the wall due to the confinement effect of the bamboo geogrid strips utilized as a reinforcement as compared to the unreinforced cases. In addition to that, as the length of reinforcement increases from 0.35 H to 0.85 H, the failure surcharge pressure and the facing deformation increase. However, for a particular surcharge load, increasing the reinforcement length decreases the facing deformation. This is attributed to the ability of longer reinforcements in load transfer mechanism and redistribution of the stresses in a wider area. Plaxis 3D has been used for the numerical simulation of the model experiments. The fly ash was modeled as linear elastic perfectly plastic material with a Mohr-Coulomb failure criterion, and the bamboo geogrid was modeled as an elasto-plastic material. Plaxis 3D overpredicts the horizontal wall movement, especially for longer reinforcements. However, it predicts the normalized settlement versus normalized failure surcharge pressure quite accurately.

Calcareous sediments are distributed approximately 40% of the world’s seafloor. Previous research on calcareous soils generally recognizes that these soils demand special consideration due to their unique characteristics such as high carbonate content and porous particle structures. Calcareous sands can experience dramatic particle damage during driving, resulting in excessive foundation settlement. Particle breakage has been considered as the most effective parameter to describe its physical behavior. To evaluate the effect of particle breakage on shear strength, triaxial consolidated drained tests were performed on calcareous sand with varying percentages of crushed material at various confining stresses. The particle size distribution of calcareous sand was determined before and after each test to check the relative particle breakage. A modified stress-dilatancy model is used in this study to investigate the correlation between the effective stress ratio, dilatancy, and particle breakage of the tested soils.

This paper examines the influence of reproducing the stress history of Hawthorn Group (HG) clays during laboratory reconsolidation on the subsequent shear stiffness degradation response under compression paths. Thin-walled Shelby tube samples of lightly overconsolidated HG clays were extracted from the Deep Foundation Test Site at the University of Central Florida Arboretum. Undrained triaxial compression tests with local instrumentation, bender elements, and Hall effect transducers, were performed to capture strains at different levels. Soil response is compared with a conventional laboratory technique where specimens are anisotropically consolidated to the in situ stress state, and no stress history of the soil deposit is reproduced. Results are evaluated in terms of stress-strain-strength responses with emphasis on shear stiffness degradation. Significant differences on the onset of shear stiffness degradation were observed for θ-values approaching 180° in concordance with the stress path rotation angle concept. Reproducing the stress history of HG clays impacts the stiffness at small strains whereas no significant differences were observed in the undrained shear strength of the material.

A shallow foundation, 3 × 3 m in plan and embedded 0.9 m, was dynamically loaded at the National Geotechnical Experiment Site (NGES) on the campus of Texas A&M University (TAMU), and the measured results were compared with results computed via four widely publicized methodologies: the cone models of Wolf and Deeks, the PILAY models of Novak and Aboul-Ella, and the homogeneous half-space models for embedded footings of Apsel and Luco and Gazetas. The cone models produced the best predictions of the measured field response, and all four methodologies produced good predictions of the vertical and horizontal motions of the foundation. The rocking motions were well predicted using cone and half-space models, while the PILAY predictions of rocking were quite different from the measurements. The Gazetas model results suggested that full embedment and full contact of the foundation and soil produced the best representation of the field behavior. It was possible to find one representative half-space modulus for the models to match the field measurements for all modes of vibration, but it was not obvious how one would determine this modulus value a priori in a design situation and without the benefit of field response measurements.

In this paper, statistical analyses were conducted to understand the applicability and reliability of conventional consolidation tests on extremely soft dredged fill material. Of all the consolidated tests reviewed, specially designed and fabricated equipment was used to perform multiple one-dimensional consolidation tests on composite slurry samples prepared from the dredged borrow area. Data of over 30 consolidation tests were analyzed and assessed, and regression equations were proposed to estimate the compression index C_c. By comparing the proposed regression equations with the existing empirical equations, it was discovered that the compression index predicted by a simple linear equation considering the natural moisture content, initial void ratio, plastic limit, and liquid limit could sensibly assess the genuine soil compression index. In any case, the consolidation test on very soft dredged soils is time-consuming and work-intensive; it is likewise observed that the use of empirical equations recommended in this research results in a valuable tool to assess the compression index of the marine clayey soils used in the wetland recovery projects in coastal Louisiana.

Submarine landslides transport thousands of cubic meters of sediment across continental shelves even at slopes as low as 1° and can cause significant casualty and damage to infrastructure. The run-out mechanism in a submarine landslide is affected by factors such as the initial packing density, permeability, slope angle, and initial volume. While past studies have focused on the influence of density, permeability, and slope angle on the granular column collapse, the impact of volume on the run-out characteristics has not been investigated. This study aims to understand how the initial volume affects the run-out using a two-dimensional coupled lattice Boltzman and discrete element (LBM-DEM) method. The coupled LBM-DEM approach allows simulating fluid flow at the pore-scale resolution to understand the grain-scale mechanisms driving the complex continuum-scale response in the granular column collapse. For submerged granular column collapse, the run-out mechanism is heavily influenced by the interaction between the grains and the surrounding fluid. The development of negative pore pressures during shearing and hydrodynamic drag forces inhibit the flow. On the other hand, entrainment of water resulting in hydroplaning enhances the flow. With an increase in volume, the interaction between the grains and the surrounding fluid varies, causing changes in the run-out behavior. For smaller volumes, the forces inhibiting the underwater flow predominates, resulting in shorter run-outs than their dry counterparts. At large volumes, hydroplaning results in larger run-out than the dry cases, despite the inhibiting effects of drag forces and negative pore pressures.

In the U.S., there are tens of thousands of road sign structures, mostly designed following the load and resistance factor design (LRFD) specifications for structural supports for highway signs, luminaires, and traffic signals (AASHTO LTS). However, due to the soil investigation being expensive and given the fact that soil investigation is not usually done prior to sign installation, subsurface soil properties are usually based on conservative engineering judgment. This estimation of soil property could lead to an uncertain system response of these structures and/or a costly over-design. Even with LRFD, the need to reduce the variation in the predicted performance of the system under applied loads is still apparent as many of the road-sign structure foundations are over-designed. In the recent years, the robust geotechnical design (RGD) methodology is developed to derive an optimal design through a careful adjustment of the design parameters so that the response of the designed system is insensitive to the variation of uncertain soil parameters (robust) while being cost efficient. This paper adopts RGD methodology for design of a footing for a road-sign structure to explore effects of inherent spatial variabilities on the design.

The application of energy geo-structures can significantly change the soil temperature. Thermal loading induces pore water pressure due to the differences in thermal expansion coefficients of the pore fluid and the pore volume. The generation and dissipation of the thermal pore pressurizations result in thermal consolidation. In the condition that the induced pore pressure cannot dissipate, reduction of the mean effective stress may cause soil shear failure or hydraulic fracturing. The result of this research will enable us to predict the pore fluid behavior in the porous media, which will be useful to understand the thermo-hydro-mechanical process in saturated soil. Thermal pressurization is studied through a series of fully undrained tests. Therefore, a temperature-controlled triaxial cell has been used to understand the relation between thermal loadings and pore pressure changes at different temperatures and for different cell and confinement pressures. Different samples are tested under different confinement stresses (345, 480, and 520 kPa) through a modified temperature-controlled triaxial cell which provides a range of temperature changes between 3°C and 80°C. Using pore pressure transducers at the bottom and the top of the samples, pore pressure changes are recorded at different temperatures. Cell pressure during the test as well as initial pore pressure of the sample is controlled with digi-flow pumps of a triaxial setup. Results indicate that the thermal pressurization rate increases for higher confinement.

A partially saturated condition resulting in a multi-phase pore fluid (air-water mixture) shapes the mechanical and hydraulic behavior of fine-grained soils. The purpose of this experimental investigation is to assess how the properties of glacial tills, utilized for a shallow geothermal project in central Illinois, change with the degree of saturation. The saturation process is a function of time and water pressure that results in the compression of the air bubbles while forcing them to dissolve into the surrounding pore fluid as the applied pressure increases. Measurements of the Skempton’s B coefficient under the undrained condition at fixed value of the effective mean stress provide the assessment of the degree of saturation. B-values are increasing with the decrease of pore fluid compressibility and eventually become constant (and ≈1 for soils) when full saturation is achieved. The implications of a partially saturated condition were evaluated by conducting undrained compression tests and permeability measurements at B = 0.05 (94% water saturation), B = 0.44 (97% water saturation), and B = 0.95 (fully saturated). The results corroborated increased compressibility and decreased permeability at partial saturation, emphasizing the importance of assessing the saturation conditions at which material properties are reported.

Cone penetration test (CPT) is a common testing method for both field and laboratory studies. A new assembled in-flight miniature cone penetrometer for centrifuge testing was proposed, developed, and applied in this study. The assembled penetrometer with low cost and easy maintenance mainly consists of a cone tip, a miniature underwater load cell, a steel sleeve, and a tail S-shaped load cell and can measure both tip resistance and sleeve friction. Penetration tests on saturated fine sand deposits were conducted under 1g and 25g conditions to check the penetrometer performances and study the sand behaviors. The results demonstrated that satisfactory performances can be provided by the penetrometer and favorable uniformity of the model deposits can be provided by water sedimentation method. The proposed assembled cone penetrometer provides a simpler and more inexpensive way to investigate the soil strength in the centrifuge testing.

The fundamentals of artificial neural networks (ANN) are implemented to develop a prediction model to simulate the mechanism of fully softened shear strength (FSS). The model is generated from a laboratory database containing 201 laboratory strength tests with FSS secant friction angle values as the output and soil properties as the inputs. The objective of the study is to detect the inputs from the parameter space that controls the response in a hierarchical manner. From the results, a variable assessment indicates that among the studied factors, the main factors affecting the FSS secant friction angle are the plasticity index, the clay fraction, and the normal effective stress. Predictor profilers and surfaces are provided as a visual way of studying how changes in the factors influence the response—the effects of the plasticity index in the FSS secant friction angle decrease after about 100% plasticity index. The clay fraction profiler shows that an increase in the clay fraction decreases the FSS secant friction angle at a constant rate. Furthermore, the strong influence from normal stress in the FSS secant friction angle decreases after a cutoff value of around 150 kPa, which agrees with the curvature of the failure envelope. Insights regarding the interaction and correlation coefficients of the studied factors with the FSS secant friction angle are given.

The New Jersey Meadowlands is roughly 80 square kilometers of wetlands, uplands, and developed areas located in the Hudson and Bergen Counties of New Jersey. The results of various laboratory tests including consolidation and shear strength tests on undisturbed soil samples collected from a total of 40 standard penetration test boreholes drilled at 17 sites throughout the Meadowlands are presented in this paper. Based on the boring logs, the subsurface profile in the Meadowlands composed of a tidal marsh deposit of thickness less than 10 m, which consists of very soft to soft peat and organic clayey silt. The major deposit in the Meadowlands is composed of very soft to medium varves of silty clay and clayey silt, whose total thickness exceeds 25 m in some areas. The consolidation tests were performed on 11 samples from the tidal marsh and 65 samples from the varved soil deposits. The laboratory data indicate that the peat soil which has an organic content greater than 50% exhibits significantly higher compressibility than the organic clayey silt with a much lower organic content. Average values of the Atterberg limits and the compression and swell indices for the varved soils are close to the typical values for the Boston blue clay. Profile of overconsolidation ratio indicates that the peat and organic soils and the varved soils below a depth of 10 m are normally consolidated to moderately overconsolidated, while the varved soils in the top 10 m are moderately to heavily overconsolidated. Published empirical correlations generally underestimate the compression and swell indices (C_c and C_s, respectively) of the varved soils; therefore, four new correlations to better estimate the values of C_c and two new correlations to better estimate the values of C_s for the varved soils in the Meadowlands are derived in this study.

Generally, the first choice in the selection of a foundation for buildings and other structures is a shallow foundation because it is more economical than a deep foundation and easier to construct. However, shallow foundations are usually considered to settle more than deep foundations. This is a fallacy as well-designed shallow foundations do not settle more than well designed deep foundations. This research aims to give guidance on selecting the soil modulus to calculate the long-term settlement of shallow foundations on clay, given a chosen probability that the calculated settlement will be larger than the measured settlement. The settlement of shallow foundations depends on the properties of the soil, the load on the soil, and the geometry of the foundation. The soil properties vary from one site to another, while the geometry of the foundation can be selected to keep the settlement due to the load within tolerable limits. In some cases, the settlement of the foundation is recorded along with the soil properties, and the data are published in the open literature. Over time, the number of such cases has increased and, if well-organized in a database, can be very useful in practice. Indeed, comparing the measured data with the predicted data can guide the practitioner in the safety margin to be used for a given prediction method. In this paper, a database of shallow foundation settlement records on clay called “TAMU-SHAL-CLAY” has been created by collecting case records from the open literature and organizing them in a spreadsheet available free of charge. The measured settlements are compared with the predicted settlements using the elastic equation while using a long-term soil modulus estimated as a multiple of the undrained shear strength of the clay. In addition to the predicted versus measured settlement comparisons, the probability that the predicted settlement will be larger than the measured settlement is presented as a prediction multiplier function. The results can help the practitioner decide at which level of probability this practitioner wishes to operate.

A by-product of the paper and wood industries, lignin is produced abundantly worldwide due to the increasing demand for wood and paper-based products. Improper disposal or storage of lignin is not only a misuse of natural resources but also poses a critical hazard to public health and the environment. Construction of highway subgrade has been identified as one of the feasible responses for consuming vast quantities of lignin to dispose of it in an ecologically sound manner, as it can be a low-cost and less energy-intensive chemical additive for soil stabilization. However, studies on the performance of lignin in stabilizing expansive soils in highway subgrade have been very constrained. Volume change resulting from seasonal moisture variations in expansive soil subgrades damages existing highways and complicates highway construction in expansive soil areas. To reduce expansive soil-induced geological disasters and utilize waste resources, the use of lignin could potentially be a sustainable solution for soil stabilization. In this research, a series of multi-scale laboratory tests were conducted to examine the Atterberg limits, the compaction and consolidation behavior, and the Fourier-transform infrared spectroscopy (FTIR) characteristics of lignin-stabilized expansive soils. The study reveals that the degree of lignin content impacts the physical, mechanical, and microstructural properties of the stabilized expansive soil. From the compression index (C_c) and swelling index (C_s) values, it was concluded that a satisfactory level of soil stabilization could be achieved by the application of an optimum percentage of lignin. The lignin-based cementing material bonds soil particles firmly together and fills the pores to produce a progressively steady soil structure.

Granular-surfaced roads comprise 73% of Iowa’s county road network. The surfaces of these gravel roads undergo mechanical and chemical deterioration over time due to extreme weather conditions and traffic loads. The goal of the present study is to improve our understanding of the mechanical deterioration that affects the performance of different geological types of coarse aggregates used in granular roads and shoulders. Samples of coarse aggregates were collected from four different quarries in Iowa. Laboratory gyratory compaction tests (GCT) were performed on specimens of the quarry samples to simulate their degradation under traffic loading conditions over time. From the results of GCTs, breakage parameters are evaluated, and relationships between dry unit weight, shear strength, and compaction energy are established for the different aggregate types examined. From these relationships, an efficient field-compaction energy criterion is determined to maximize density and shear strength while minimizing over-compaction and breakage of the aggregates.

The use of open-graded aggregates (OGAs) as structural backfill has become more common in the construction of bridge abutments, retaining walls, and as base layers in pavement applications. The Federal Highway Administration (FHWA) has conducted considerable strength testing of the AASHTO M 43-05 OGA gradations; however, the testing has largely been limited to locally sourced aggregates, with all tests conducted on a single type of large-scale direct shear (LSDS) device. Therefore, FHWA initiated an interlaboratory round-robin LSDS testing program to evaluate the variability in the results due to the difference between testing devices, technicians conducting the test, and source mineralogy. Six laboratories were involved in this study, testing AASHTO No. 57, No. 68, and No. 8 diabase aggregates. This paper describes the round-robin testing program and equipment differences and presents the results along with a statistical analysis of the peak, tangent, and constant volume friction and dilation angles.

The performance of granular-surfaced roadways is greatly affected by annual freeze-thaw cycles, which can cause severe structural damage to the road surface. The collection of in situ subgrade soil temperature and moisture data as well as local weather data is very important to improve our ability to understand and predict subgrade behavior during freeze-thaw cycles. In this study, the use of data from a weather station installed adjacent to a granular road test section is compared to data interpolated from the two nearest weather stations of a statewide network, to compare their performance as inputs for freeze-thaw simulations using the simultaneous heat and water (SHAW) model. The subgrade temperature and moisture content predictions from the simulations are compared to those measured by sensors installed at several depths below the soil surface at the center of the test section. The results suggest that using weather input data from the statewide weather station network may result in reasonably accurate predictions from SHAW simulations.

The resilient modulus (M_R) is one of the most important indicators of performance of geomaterials used in pavement foundation design, and since designed pavements often are not able to fulfill their service life, researchers have been led to evaluate the procedure of resilient modulus characterization of geomaterials used in pavement foundations systems. A preliminary study was conducted on a granular aggregate base material to determine whether conventional M_R testing simulates actual stiffness behavior of these materials under actual traffic loads. The results of this study showed that the conventional testing equipment used to measure M_R did not simulate actual field behavior of geomaterials because it fails to take into account anisotropic stress conditions, suggesting a need to produce more realistic experimental results by measuring and monitoring anisotropic stress conditions during testing. To respond to this need, a series of advanced M_R tests were conducted using a custom designed and manufactured dynamic polyaxial testing system that enabled measurement of the resilient modulus of materials in both vertical and horizontal directions. It was observed that the geomaterial had different stiffness values at each direction and that the ratio of vertical stiffness to horizontal stiffnesses (modular ratios) can be defined to produce a better understanding of the performance of geomaterials used in pavement foundation design. It is believed that the findings of the study will enhance the long term performance and service life of designed pavement systems.

Aggregate durability is crucially important for performance of granular roadways. Therefore, proper laboratory durability evaluations of aggregates that will be used during construction and maintenance of granular roadways are very critical. Los-Angeles (LA) abrasion and Micro-Deval tests were two conventional methods that are used for laboratory during tests. However, it is very well known that these tests are not adequate to simulate the durability of aggregates under vehicle and compactor loads. The current study proposes to use the gyratory compaction method to evaluate the durability of aggregate materials. During gyratory tests, gradations, shear resistances, void ratios, and maximum dry unit weights of each material were monitored before and after tests. The results of this study showed that the fines content of the materials did not change significantly, while the gravel and sand contents of all materials changed considerably. It was also observed that the energy required to gain the optimum void ratio and dry unit weight were always higher than those required for the modified and standard Proctor tests energy levels. However, two out of three materials achieved 90% of the maximum shear strength at lower energy levels that were required for the modified Proctor test.

An insulation layer on the top of the frost-susceptible soil has been proved as an efficient strategy to mitigate frost heave and thaw weakening for pavement in cold regions. To investigate the heat-transfer process in insulated pavements and compare the performance of different insulation materials under similar environmental conditions, we build five large-scale (4 ft by 4 ft by 3 ft deep; or 1.21 m by 1.21 m by 0.91 m deep) insulated pavement samples using different insulation materials. One of the samples is a control sample with no insulating layer, while the other four samples are insulated by extruded polystyrene (XPS) boards, tire chips, foamed concrete, and foamed glass aggregates (FGA), respectively. We place a frost panel on the top of each sample to control the freezing process from the surface. We adopt two types of environmental conditions, including constantly freezing and natural freeze-thaw environment with internal temperature distribution monitored by embedded thermocouples at different depths. Experimental results indicate that the insulation layer has a significant impact on the temperature distribution in both layers above and below the insulation layer. By comparing the thermal performance of the control sample and insulated sample under two environmental conditions, the XPS board is more suitable to utilize as an insulating layer compared to other insulating materials, followed by tire chips, foam glass aggregates, and foamed concrete.