Geo-Congress 2022: Advances in Monitoring and Sensing; Embankments, Slopes, and Dams; Pavements; and Geo-Education

Soil moisture has a strong influence on the stability of shallow colluvial hillslopes. Thus, it is often necessary to monitor seasonal variations of soil moisture at individual sites of interest. This work demonstrated a workflow showing that satellite-based soil moisture data can be downscaled through machine learning and used as a source of data for landslide stability analyses. In particular, the NASA Soil Moisture Active Passive (SMAP) Level 4 Root Zone Soil Moisture (L4_SM) product provides near-real-time measurements of soil moisture on a gridded spatial resolution of 9 km. Such resolution, however, is too coarse for soil moisture measurements at a single site. Therefore, satellite-based soil moisture data must be downscaled for use in slope stability assessment at individual sites. This study used a machine learning (ML) technique, Random Forest Regression, to downscale the SMAP Level 4 Root Zone Soil Moisture product and applied the results to landslide slope stability analyses. We modeled the L4_SM data based on 1 km NASA Moderate Resolution Imaging Spectroradiometer (MODIS) products. First, the MODIS products were upscaled from 1 km to 9 km and used as features, combining with L4_SM data as labels to train the Random Forest model. Then, the L4_SM data were downscaled from 9 km to 1 km through the trained model and locally calibrated to that of ground-based data by linear regression. The processed SMAP data were served as the input of an infinite-slope stability model, which was used to investigate incipient slope failure conditions. The slope stability results were verified using known landslide occurrences in the Commonwealth of Kentucky. Results of this work showed that the stability models constructed using downscaled L4_SM data functioned well at detecting incipient conditions at the investigated sites. The purpose behind this study was to develop a process flow routine through which SMAP L4_SM data can be downscaled through machine learning as well as investigating the potential efficacy of utilizing downscaled L4_SM to conduct landslide stability analyses.

The potential use of synthetic aperture radar (SAR) imagery for estimating moisture contents at sandy beaches is discussed. These systems are considered all-weather satellites, can provide data during storm events, and allow for the monitoring of sandy beaches during adverse conditions. SAR images are composed of the backscatter coefficient, which is a representation of the returned energy. It is impacted by radar properties (wavelength of the transmitted signal, incidence angle, and polarization) and terrain characteristics (dielectric properties, surface roughness, and feature orientation). Typical trends in backscatter, moisture content, surface roughness, and roughness category are presented for a case study from the sandy Atlantic beach in Duck, North Carolina, and potential models how to address these factors in a data analysis framework are discussed. Moisture contents here ranged from 3.7% to 23%, backscatter coefficient ranged from –20.5 dB to –13.3 dB, and standard deviation of the surface height variation (or RMS height) ranged from 0.101 to 0.491 cm. Preliminary results indicate that SAR images are a feasible option for the derivation of moisture content data, especially for images collected at intermediary incidence angles (~30°–46°).

The Cobbs Creek Regional Water Supply Reservoir is a new pumped-storage facility just south of the James River on Cobbs Creek in Cumberland County, Virginia. Construction began in July 2017 and is expected to be completed in 2022. The project includes the construction of three zoned earthen embankment dams to impound Cobbs Creek, including a 3,850-foot-long main dam with a maximum height of 160 ft, a 1,200-foot-long saddle dam with a maximum height of 25 ft, and a 900-foot-long access road dam with a maximum height of 15 ft. Performance of the dams during initial filling and long-term operation is monitored with an extensive geotechnical instrumentation program that includes 32 vibrating wire piezometers, seven seepage collection vaults with vibrating wire water level monitors, a fiber optic distributed temperature sensing system, and survey monitoring points. The electronic instruments will be monitored using an automated data acquisition system that includes a central automated datalogger connected to a local enterprise appliance server platform. Communication between the electronic instruments and the datalogger will be accomplished through a wireless mesh network consisting of data transmission points and signal repeaters. This paper provides an overview of the instrumentation system design and data collection. While the paper will focus on the Cobbs Creek project, the monitoring challenges and solutions presented are common for many dam rehabilitation and new dam construction projects. The objective is to share the approach and lessons learned from this project to benefit owners, consultants, and regulators on their projects.

Despite the rise in popularity of jointless bridges, their behavior is still not well understood. By eliminating expansion joints at the ends of the deck, the abutment backfill is affected by daily loading cycles due to thermally induced strains, leading to earth pressure ratcheting and backfill settlement. This study presents three years of monitoring data of a semi-integral bridge in Texas. This bridge was instrumented using a combination of earth pressure cells, laser distance meters, and temperature sensors. In this study, the effect of temperature variations on the evolution of earth pressures acting on abutment walls is evaluated. Results indicate that it is generally during the cold months that comparatively high increases in earth pressures develop, which do not necessarily lead to a symmetric response between the two abutments. Additionally, stress ratcheting was found to lead to excessive deformations in the wingwalls and loss of aggregates for the conditions that corresponded to the abutments under investigation.

This study aims to develop small-size, energy-efficient, and low-cost sources for a bio-inspired underground communication system using seismic waves. Inspired by how animals generate substrate-borne vibrations, two different vibrational sources were designed, fabricated, and evaluated. One source is inspired by tremulation and it features an enclosed vibrator; the other is inspired by drumming and it features an enclosed solenoid. The two sources were then used to transmit plain text files and image files in dry sand. The data files were first converted to binary streams and then encoded using on–off keying modulation, based on which the vibrational sources were controlled. The results showed that a 0.6W tremulation-inspired vibration source could send clear signals up to 70 cm in loose dry sand, but it would encounter a jamming problem when the embedment depth was high. Even though it is hard to control the solenoid to sub-milliseconds precision, the drumming-inspired vibrational source performs well at depth and at distance. It can serve as a high-quality source for a vibrational underground communication system.

Distributed Acoustic Sensing (DAS) is a fiber optic sensing system used for vibration monitoring. This study investigates the effects that soil type, temperature, moisture content, time, and loading have on DAS performance. Impact testing was performed along a buried fiber optic array for over one year to induce a DAS response, which was evaluated using Signal-to-Noise Ratio (SNR). The results indicate that portions of the array in gravel consistently out-perform portions of the array in other soil types. Neither soil moisture nor temperature appear to have a significant effect on SNR. An increase in ground surface load was observed to increase SNR. A significant change in performance occurred while testing paused from March 2020 to August 2020 due to the Covid-19 pandemic. The observed changes highlight how DAS could be used for infrastructure monitoring, where such changes could possibly prompt a localized site inspection. Performance of a decade-old portion of the DAS array remained consistent and strong, suggesting that DAS has long-term viability.

The development of low-cost sensors such as miniature electro-mechanical systems (MEMS) accelerometers has allowed for new and innovative monitoring applications in civil engineering. Within the realm of geotechnical engineering, these low-cost sensors have been utilized to monitor wave propagations in soils, for tilt monitoring, and for structural health monitoring purposes. In this study, custom-built three-axis accelerometers utilizing low-cost accelerometer breakout boards manufactured by Adafruit with ADXL326 and ADXL335 accelerometer chips were constructed, calibrated, and then used on an active construction site to monitor the dynamic behavior of a compaction roller during construction activities. The goal of this paper is to provide interested readers with a step-by-step guide on how to construct these low-cost accelerometers, which are housed in a custom 3D printed mold and hermetically sealed utilizing epoxy that is readily available at commercial hardware stores. In this study, the custom-built sensors were calibrated utilizing a simple 6-point static calibration procedure, with the measured calibration waveforms being compared to those measured from an industrial grade accelerometer for validation purposes. The study also presents preliminary results showing the capabilities of these sensors for measuring the accelerations of a vibrating compaction drum during soil compaction; these types of sensors offer significant utility for studies that are exploring continuous compaction control or intelligent compaction of soils, asphalt, roller-compacted concrete, or other similar civil engineering materials that are placed using vibratory drum compaction.

Distributed Acoustic Sensing (DAS) systems, typically consisting of a fiber-optic cable and an optical time-domain reflectometry interrogator, are commonly used to detect vibration in the medium surrounding the fiber-optic cable. DAS has been used for over a decade as a low-cost sensor for infrastructure monitoring in oil and gas pipelines. For confidence in DAS as an infrastructure monitoring system, it is important to recognize signal changes with time due to environmental effects. Previous research has explored the long-term changes in system performance. The purpose of this research is to document changes in DAS performance, with signal-to-noise ratio (SNR) in decibels (dBs) as the performance metric, for five data collections throughout each of two days approximately one month apart. One day was dry, and the other day was wet, having experienced over 3 in. (80 mm) of rainfall. The DAS system is installed in a trench containing gravel, sand, flowable fill, and native loess sections. Moisture and temperature sensors in each fill material report hourly average volumetric water content and soil temperature, while a nearby weather station collects hourly rainfall and air temperature data. A calibrated hammer on a metal plate was used to generate seismic waves directly above portions of the array in each fill material, thereby inducing vibrational strains in the fiber-optic cable. These signals were then compared to the noise in the associated cable section immediately before the hammer strike sequence. Results show significant changes in SNR values throughout the day. Consistent with previous research, the gravel trench had the strongest SNR, and the flowable fill had the weakest. While the test trenches were fully saturated on both study days, SNRs on the dry day (a day without precipitation) averaged several dBs higher than on the wet day (a day with precipitation). Variations in SNR within a material over the course of the day were significantly greater on the wet day than the dry day, but the variations within the day do not seem to be correlated to temperature or active rainfall. Understanding diurnal variations in DAS performance will inform the structural health monitoring community to better interpret system results.

Solid-state lidar incorporated into phones and tablets is an emerging remote sensing technology that drastically reduces the cost of generating 3D point cloud data with lidar. Recent studies have shown that 3D point cloud data can be used as part of soil density testing that involves excavating a test hole and measuring the hole volume. Lidar is used to determine the hole volume as a substitute for a volume replacement material such as sand or water. In this way, low-cost lidar has the potential to significantly simplify and accelerate the density testing workflow compared to a traditional sand cone test, without the burden of licensing, security, and training associated with the nuclear density gauge. Here, we describe a proof-of-concept field trial using a solid-state lidar-equipped tablet to measure in-place soil density at an embankment dam rehabilitation project in the northeastern US. The lidar-based density measurements compare reasonably with densities obtained using a nuclear density gauge on the same material. The proposed methodology requires limited additional training, low-equipment cost, limited scanning time, and no consumable materials when compared to other in-place density approaches.

Owing to the opportunity that the 2020 global COVID pandemic provided for safe flight of UAVs over a nearly unpopulated campus, a massive 3D Structure from Motion photogrammetry modeling project for all of Brigham Young University main campus was conducted resulting in the creation of an 80,384 photo, 1.65 trillion-pixel texture, hyper-realistic model that is visible for public display, study, and interaction on a simple internet browser. Cost effective terrestrial DSLR imagery coupled with autonomous unmanned aerial vehicle (UAV) flight and additional manual flights enabled us to image not only a large area, but capture high detail of structure walls, under-hangs, and other commonly missed or distorted features is common photogrammetric 3D reconstructions. Temperature, exposure, and shadow image post-processing greatly enhanced model alignment and aesthetics while 161 Ground Control Points provided accuracy, which was assessed with 116 check points to have an average 3.3 cm error. The final campus model provides a 3D digital snapshot of the historic COVID-19 pandemic and creates the framework for future VR/AR tours/experiences, campus planning, smart campus integration, and other uses.

Photogrammetry is gaining popularity in geotechnical engineering. Many researchers used photogrammetry to measure the soil volumes in laboratory tests. However, the potential of using low-cost security cameras in measuring the volume changes of unsaturated soils during triaxial testing has been largely unexplored. This paper presents a feasibility study on developing a multi-security camera photogrammetric method to reconstruct the 3-D models of the soil sample and track the continuous deformations of soil specimen during triaxial testing. Sixteen low-cost security cameras are installed to the steel ring around the triaxial test equipment. Coded targets are posted on the surface of the acrylic chamber and frame rods. The membrane is printed with coded targets. There are two stages for the proposed method. The first stage involves performing single camera-based photogrammetry before the triaxial test. A MATLAB program is developed to detect the coded targets automatically. Then, these coded target detection results are fed to a three-dimensional reconstruction program to determine the three-dimensional points in the air. The stations for each security camera can be back calculated. These camera stations will be used in the next stage for three-dimensional reconstruction. After that, multiple ray tracings are applied to determine the three-dimensional points on the soil specimen under water. The second stage for the proposed method involves multi-camera-based photogrammetry during the triaxial test. The security cameras record the whole testing process synchronously from multiple locations and orientations. Image processing is used to track the centroids of the coded targets. Ray tracings are applied again to determine the three-dimensional points on the soil specimens during the triaxial testing. Experimental results indicate that the proposed method can obtain accurate 3-D model of the soil specimen using relatively low-cost security cameras. In addition, the proposed method takes videos of the whole triaxial test, which can track the specimen deformations at every moment during the test.

With terrestrial interferometric synthetic aperture radar (InSAR), geostructures can be monitored in real time with an unparalleled combination of accuracy and spatial resolution. However, the displacements obtained with InSAR are 1D in the line-of-sight direction, and thus offer limited insight concerning the causative deformation mechanism. This study summarizes a novel approach for obtaining 3D displacement vectors by combining measurements from InSAR and 2D Feature Tracking. The method is referred to as InSARTrac. Controlled laboratory tests indicate a 3D accuracy of 0.05 mm at a range of 13 m. Initial field tests conducted for this study, involving known displacements of a radar corner reflector, show a 3D accuracy of 0.5 mm at a range of 150 m, which is comparable to the accuracy obtained with the reference total station measurements.

The May 19, 2020, Edenville Dam failure in Michigan led to the failure of the Sanford Dam and subsequent flooding of communities downstream. As part of immediate field reconnaissance activities, remote sensing using Uncrewed Aerial Vehicles (UAVs, more commonly known as Unmanned Aerial Vehicles) equipped with optical and infrared sensors were deployed, and the results are presented herein with emphasis on the infrared data, which is not yet extensively used in geotechnical engineering. It is shown that the infrared imagery, which provides an estimate of material temperature, along with 3D models derived from optical data was successful in classifying different soils (such as gravel fills, sandy soils, and clayey soils) and other materials encountered at the dam. Gravelly fills systematically exhibited the highest temperatures, clayey soils the lowest temperatures, with sandy soils having intermediate temperatures. In addition, infrared data were used to identify wetter areas, or locations where through-seepage was observed within the dam study area, as well as to assess the gravimetric water content of soil materials.

An expert panel concluded the sudden failure of Feijão Dam 1 in 2019 was triggered by ongoing creep combined with strength reduction in the unsaturated zone due to a loss of suction caused by heavy rainfall toward the end of 2018. This paper presents numerical modeling of the failure using the PM4SiltR viscoplastic constitutive model in the finite-difference program FLAC. A brief description of the dam history, construction, and the observed failure is provided. The constitutive models and their calibration for the fine tailings, coarse tailings, foundation soil, and berm materials are described. Simulations are presented that model the observed changes in loading conditions prior to the observed failure. Results of the analyses show the failure patterns, triggering mechanisms, and deformation magnitudes are in reasonable agreement with the observed failure. Limitations of this study and implications for practice are discussed. The results of this study provide support for using this model when assessing static slope stability of embankments containing strain softening materials.

Excessive vertical and lateral movement of embankments can result in damages to structures founded on and adjacent to the embankments. One-dimensional analytical methods are available to estimate the settlement of embankments; however, the lateral displacement is more difficult to determine. Numerical modeling is typically required to predict lateral deformation. Instrumented test embankments can be modeled to evaluate the efficacy of various soil constitutive models and numerical techniques used for these predictions. One such test embankment was constructed by the Malaysian Highway Authority over a Muar clay deposit. The embankment was instrumented with settlement plates, inclinometers, and piezometers. The embankment was then rapidly loaded to failure. To predict and better understand the behavior of the embankment, the Dafalias-Herrmann Bounding Surface model for isotropic clay soils has been implemented into PLAXIS 2D. The model was able to accurately capture the settlement behavior as the embankment approached failure. The excess pore water pressure was measured at discrete times during the construction and has been captured reasonably well by the model. The lateral deformation of the foundation soils was initially overpredicted and then underpredicted as the embankment approached failure. For comparison, the embankment was also modeled using the Modified Cam Clay model.

In soil-structure interaction studies, which include dam safety analyses, realistic modeling of the interface between concrete and coarse-grained soil is an important component. This includes, but is not limited to, the interaction between the concrete face slab with the neighboring cushion layer in concrete-faced rockfill dams (CFRDs). This paper focuses on data from an experimental program that is investigating soil-structure interface behavior at a large laboratory scale with appropriate boundary conditions. Global measurements of force-displacement along with local observations were evaluated for three different surfaces in contact with crushed limestone. While many researchers have investigated concrete-sand and steel-gravel interfaces, there is limited data on concrete-gravel interfaces. Tests on these surfaces, including smooth concrete, rough concrete, and a waterproofing membrane, were performed under a range of normal pressures, and the coefficient of friction was characterized for each interface. Experiments revealed that shear strength increased proportionally with normal pressure and that a minimal increase in concrete roughness increased the interface friction coefficient by a factor of nearly 1.5. The results on the membrane-gravel interface varied between the smooth and rough surface measurements. The rolling of particles was the dominant behavior under the concrete block, and a heap clearly forms in front of the block, which could be the cause of damage to CFR dams that have been subjected to seismic loads.

The Old River Low Sill Structure (ORLSS) is located approximately 25 mi south of Vidalia, LA, and is part of the Old River Control Complex. The structure is founded on steel piles and is a 566-foot-long concrete structure constructed in 1959. The structure resembles a dam with 11, 44-foot-wide gates to prevent migration of the Mississippi River’s current course to a hydraulically shorter course down the Atchafalaya River. A re-analysis was undertaken by the US Army Engineer Research and Development Center to investigate the current level of stability and the potential for adjusting the operating limitations placed on the structure because of damage during the 1973 flood. The investigation was performed by reviewing the design and post-design stability analyses, analyzing performance data, and performing an updated stability analysis. The stability analysis was performed with monitoring data that spanned several decades. Using historic monitoring data in the stability analysis, with a wide range of loading conditions, it was shown that uplift conditions were not as severe as previously considered. Performance data coupled with the stability analysis show that the structural performance supports the current operating conditions.

This paper describes the centrifuge model construction procedure for an embankment on a soft clay profile reinforced by Soil-Cement (SC) columns and presents preliminary results and observations of the ground and embankment responses. Centrifuge model corresponded to, in model scale units, a 12 cm embankment with a relative density of 80% underlain by a 23 cm soft clay layer. Three rows of floating SC columns with a diameter of 2 cm and spacing of 2.4 cm were installed below the embankment toe. The centrifuge modeling procedure including soil consolidation, SC column mix design, and their installation under the embankment toe is described in detail. The results indicated that the prominent failure mode of low-strength SC columns is tension-bending failure. In addition, it was observed that the embankment crest experienced large settlement due to lateral deformation of the foundation soil and SC columns.

Scour of rock by hydraulic plucking is a critical issue facing many of the world’s dams at which excessive scour of the dam foundation or spillway can compromise their performance. However, the mechanisms that govern plucking are not fully understood, and scour assessment methods are either highly empirical or significantly simplified. Here, a numerical approach is presented that directly models fluid-solid interaction during scour by modeling the fractured rock mass using the Discrete Element Method (DEM) and the Lattice Boltzmann Method (LBM) for simulating the fluid. Often flow over spillways is highly turbulent, requiring numerical methods that can accommodate high Reynolds number flows. As such, Large Eddy Simulation (LES) has been implemented in the LBM to account for the kinematic energy dissipation at scales that are not resolved by the grid resolution in the fluid model. This approach thus can explicitly model particle geometry and how this influences fluid-solid interaction such that local site conditions and how they contribute to the likely mode of scour can be expressly evaluated. This can provide valuable insight into which strategies are most effective in addressing scour risk in dams and structures interacting with water based on site-specific conditions.

The failure of earthen dams and levee structures are mostly caused by hydraulic erosion measures including overflow (surface) or piping (internal). Several research have attempted to control and mitigate surface and internal erosion of waterfront geotechnical engineering structures via seepage control and soil shear strength improvement. Meanwhile, microbial biopolymer-based soil treatment (BPST) is gaining attention as a new environmentally friendly method to amend the geotechnical engineering properties of soil in terms of: strength improvement, hydraulic conductivity reduction, erosion resistance enhancement, and surface vegetation growth. In this study, BPST has been attempted to improve the overall stability and erosion resistance of earthen levee structures, where severe overflow and internal piping conditions were simulated by a laboratory open-channel hydraulic flume apparatus. Small scale (50:1) levee models were prepared with different BPST (e.g., biopolymer contents) treatment conditions. Surface erosion has been simulated by allowing continuous overtopping, while internal erosion (piping) has been considered by initiating internal leakage through a pre-drilled hole along the bottom of the levee model. The erosion amount (volume and mass) with time has been monitored for all test conditions. The results show BPST having a significant effect on reducing both surface and internal erosion of an earthen levee structure with a small biopolymer quantity and treatment proportion compared to the entire volume of the levee model.

Slope failures occur along state roads and highways costing the Texas Department of Transportation (TxDOT) millions of dollars in repairs every year. Texas highway slopes built on high-plastic clays experience cycles of wet and dry seasons annually. The highway slopes usually fail after a prolonged rainfall event due to rainwater infiltration into the soil. Slope failures cause serious damage to highway infrastructure like guardrails, pavement, and shoulders. Highway slope failures are mostly shallow in nature (1.2–1.8 m) but, in some cases, there are deeper slope failures (>2.4 m). Recycled Plastic Pin (RPP) has previously been utilized as a sustainable and cost-effective slope repair method by TxDOT to stabilize shallow slope failures. The objective of the proposed study is to utilize RPP to stabilize general slope failures. A failed slope located at the intersection of northbound side of Interstate 820 and Rosedale Street in Fort Worth, Texas, was selected for the current study. The selected slope failed several times during a period of two months before repair, and the estimated failure depth was between 2.13 and 3 m. A 37 m section of the failed slope was stabilized with RPPs. To stabilize the reoccurring slope failure, few rows of RPPs were driven into deeper depths (up to 4.6 m) using a layered system of pin installation. Since the slope was stabilized using RPP (more than a year ago), the slope section has not experienced any failure.

Super Heavy Load (SHL) vehicles typically carry heavy loads that exceed the permissible truck weight/size limits set forth by state highway agencies. Operation of wide SHL trailers with heavy wheel loads and non-conventional axle arrangements can potentially jeopardize the stability of pavement shoulders. This study presents a methodology for assessment of the stability of sloped pavement shoulders under SHL vehicle operations. The proposed approach extends the conventional Limit Equilibrium Method (LEM) to a probabilistic methodology that accounts for the uncertainties associated with shear strength properties of pavement unbound layers. Another major point of departure of the proposed methodology from the traditional LEM pertains to its capability for handling the demanding loading conditions imposed by SHL vehicles. To accomplish the research objective, initially, the authors devised a plan of field testing to collect relevant information on traffic loading conditions, pavement layer properties, and shoulder characteristics in ten representative sites in overload corridors in Texas. Subsequently, this information was incorporated into a 3D finite-element system to calculate the horizontal driving forces applied to the pavement shoulder due to SHL vehicle movement. A Monte Carlo Simulation (MCS) was then used to randomly generate the shear strength parameters of the base and subgrade layers. Ultimately, the resisting shear forces were compared with the sliding forces along the trial slip surfaces to determine the probability of failure for the sloped shoulders, with consideration of the SHL-induced surcharge loads, weight of the sliding block, and lateral earth pressure from the adjacent soil. The results underscored the significance of the wheel load and shoulder slope in stability analysis procedure, as operation of SHL vehicles with higher load magnitude on tires resulted in a substantial increase in the probability of failure for pavement shoulders with steep side slopes. The proposed approach can provide means to assess the potential risk against failure of sloped shoulders subjected to SHL vehicles, considering the non-conventional axle assembly of SHLs, and unique characteristics of pavement shoulders in the network.

The process credited for high efficacy of embankment pile support systems is the formation of soil arches in the embankment fill. The specific system considered in this presentation is one with cap beams over rows of columns inserted through soft clay to support an embankment fill. Such a system lends itself to a two-dimensional analysis. A formation of distinct arches, as conjectured in many design approaches, was not confirmed. However, based on the calculated stress distribution and the major principal stress trajectories, one can identify “dispersed” arches spanning the distance between two neighboring cap beams. The dispersed arching was not identified in low embankments, whereupon the settlement of the soft soil, a collapse mechanism propagated through the entire embankment height causing differential settlement of the embankment crown. This study was focused on the efficacy of the pile support system and on better understanding of the mechanisms behind the differential settlement at the crown of the embankment.

Joint design for municipal water, wastewater, and storm pipes has largely focused on satisfying index tests, without estimation of kinematic (e.g., rotation) or static (e.g., shear force) demands, and no direct evaluation of whether demands will exceed kinematic and static capacities. An overview is presented of recent studies to establish the nature and magnitude of the expected demands under differential ground movements, and to develop joint performance tests to quantify resistance capacity of the joint. Experiments on buried PVC, reinforced concrete, and vitrified clay pipes subjected to differential ground movements have been used to evaluate joint rotations and shear forces, as well as to record when leakage initiates; tests on other pipe types are planned. A joint testing apparatus from a recent project was then used to study joint leakage under combinations of shear force and joint rotation, introducing the new concept of ‘leakage envelope’. This should support work defining limits to ground movements that specific jointed pipelines can tolerate.

Incorporating recycled materials (i.e., recycled rubber crumbs, RC) and mining wastes such as coal wash (CW) and steel furnace slag (SFS) in rail tracks helps to improve the track stability, while minimizing the stockpiling of these waste materials. This paper presents two novel methods to use the blended waste materials to replace conventional subballast/materials in rail track substructure, namely (1) SFS-CW-RC mixtures, and (2) CW-RC mixtures. Two series of cyclic triaxial tests were conducted to investigate the cyclic loading response of the mixtures with different RC contents, including deformation, resilient modulus, shear modulus, and damping ratio. Test results show that CW-RC mixtures are more compressive and present less resilient modulus and shear modulus than SFS-CW-RC mixtures for a given RC content. It is recommended that 10% RC is a preferable percentage for both mixtures according to their deformation behaviour, the resilient modulus, and the damping ratio.

Pipelines transporting essential fluids such as water, gas, and oil, usually traverse thousands of miles and they may experience permanent ground deformations (PGDs) induced by landslide, lateral spreading, or fault movement. Pipelines crossing these areas are subjected to longitudinal tensile and compressive stresses applied by relative soil-pipe displacement. The slip resistance developed at pipe-soil interface and along the pipe depends on several parameters such as soil type, density of backfill, rate of movement, and pipe coating conditions. This study utilized a series of pull-out and jacking lab-scale testing setup to evaluate the effect of soil type on slip resistance of buried pipelines. Two types of sandy (SC) and clayey (CL) soils at pipe level were considered as backfill materials. In these tests, a series of uncoated buried steel pipes, instrumented by a loadcell and displacement transducer, were axially moved into and from a soil container with a constant rate of movement. The results from these experimental tests showed that the clayey backfill mobilized 50% more ultimate slip resistance against the pipe movement. The residual slip resistance for pipes surrounded by clayey soil decreased abruptly and up to 45% more after the yield point compared to the pipes buried in sandy backfills. The slip-resistance results were compared with empirical design guidelines and practical recommendations are also discussed.

Frost heave creates systemic failures in roadways, buried pipelines, and cold storage facilities across the United States and around the world. Significant frost heaving may occur when the following three conditions are met: (1) there are sustained freezing conditions, (2) the soil is frost-susceptible (typically silt-sized), and (3) there is access to water. Under these conditions and depending on the temperature gradient pore water freezes into ice lenses that grow in the direction of heat loss, causing heave. When the temperature increases during the spring season, the ice melts inducing thaw settlement and causing a reduction in soil strength. The nature and extent of frost heave vary according to the availability of water, pore fluid composition, rate of heat loss, and soil type. Similarly, soil properties influence the rate at which water is attracted to a growing ice lens and the temperature at which ice formation occurs. Laboratory tests can discern the significance of freezing intensity and duration as well as soil properties, including mineralogy, grainsize distribution, and pore fluid. As part of a larger nationwide project, the current study evaluates the frost heave potential of soils collected from Alaska, Iowa, and North Carolina. Cylindrical soil samples were given free access to water and subjected to two freeze-thaw cycles. Total heaving, heave rate, temperature profile, frost penetration depth, and its rate were measured as a function of time. Water intake during testing was also measured. The results of the study showed that amount of silt and clay content in the soil have a direct effect on the frost heave phenomenon. Soils that have higher silt content and less clay content had higher heaving. It was determined that all the soils were highly frost susceptible and had high-heave rates up to 28.4 mm/day. The maximum frost penetration depth and frost penetration rate were 114 mm and 260 mm/day, respectively.

With climate change frequency of extreme disasters is increasing day-by-day. Excessive rainfall causes shallow landslides during such extreme events, very commonly on highway slopes containing highly plastic clay. Mississippi results in a perfect area to study the Vetiver System (VS) performance for shallow slope failure under excessive rainfall, with an average annual rainfall intensity higher than other neighboring states in the south. A highway slope in Mississippi containing high-plastic clay is explored throughout the year 2019, where time-dependent slope movement along the depth is monitored with rainfall variation. A 9.1 m slope inclinometer along with a rain gauge and an air temperature sensor have been installed at that section. The slope has experienced a shallow movement at the slope surface with a depth of 1.9 m with already observed rainfall intensity. A 6 m² area of the slope is selected and reinforced with Vetiver grass. Nevertheless, quantitative studies of how much contribution the VS provides to slope stabilization in the field are still relatively scarce. The current paper presents a comparative study of the VS performance on the shallow slope movement in expansive soil observed from inclinometer data for the last two years. It is observed that due to Vetiver grass, the slope movement rate has reduced to 2% since plantation of Vetiver grass from that of 10% before Vetiver grass. Later, this result is further verified through a numerical investigation where Vetiver grass is simulated by changing soil property. Numerical analysis indicates root reinforcement from the root dimensions increases slope stability up to 30%. This study outlines an approach for the study of VS in terms of contribution to slope stabilization, including field observation and numerical analysis.

As part of a $26 million infrastructure project, twin 508 mm (20-in.) water mains were installed under Eastchester Bay, Bronx, NY. These mains provide increased capacity and redundancy for water supply to the residents and businesses on City Island. A traditional surface-to-surface HDD operation was planned; however, there was insufficient space available at the exit side of the drill path. In response, the vertical alignment was lowered, a cofferdam was constructed, and all drilling operations were conducted from the entry side. The cofferdam was sized to accommodate the installation and removal of drill steel segments and tooling more than 12.2 m (40-ft) below mean sea level. The project team required a cofferdam that would minimize water inflow to reduce around-the-clock manning of pumps as well as to mitigate the negative impact of salt water on the drilling operation. With early collaboration of all parties, the contractor was able to install a successful cofferdam with the best technology for the challenging site conditions.

Seismically induced ground deformations are observed to cause damage to the bridge superstructure and its foundation. Piles and pile groups may experience excessive lateral permanent displacements and loads, which translate into various mechanisms of potential damage to the bridge. In an attempt to reduce the detrimental consequences of such ground deformations, a number of bridge configurations are suggested, in which: (1) the foundations are placed at locations of potentially lower lateral deformations, (2) a shallow foundation is employed, (3) the bridge deck is employed as a strut to shore the slopes on both sides of the canyon, and (4) the canyon slopes are braced using the bridge superstructure and its foundation. In this study, the characteristics of the involved lateral ground deformations are discussed. On this basis, schematics of the proposed bridge configurations are presented. Furthermore, illustrative idealized two-dimensional (2D) finite-element computational simulations are included, motivated by observations from post-earthquake reconnaissance data. The presented outcomes and conclusions provide insights for bridge retrofit efforts or for new construction.

This paper presents an evaluation of the seismic response of a full-scale rail embankment tested on the University of California San Diego (UCSD) Powell Laboratory shake table. The goal of performing the experiment was to understand the impacts of earthquake motions on the seismic settlement of the embankment and the associated crosslevel variation of the rails. The tested specimen consisted of a half-section embankment consisting of layers of compacted ballast, subballast, and clay subgrade having a total height of 1.50 m and a length in the direction of shaking of 7.52 m to accommodate typical rail embankment slope angles. The specimen had a width of 3.5 m that permitted 5 ties to be connected to the rails. After characterizing the dynamic deformation response of the container designed, a rail embankment specimen was constructed and tested under an actual earthquake motion. The applied motion induced a maximum horizontal rail acceleration of 1.38 g but only a small residual cross-level variation of only 0.66 mm was measured.

Buried transmission pipelines generally traverse long distances, which potentially increase their susceptibility to geotechnical hazards. Geohazards triggered by permanent ground deformation (PGD) in the vertical plane, e.g., subsidence, frost heave, thaw settlement, and uplift, can potentially induce large plastic strain on buried pipelines. Not only the magnitude and direction but also the pattern of this vertical ground movement can result in different pipeline strain demands, which are crucial for assessing the structural performance of pipelines. This paper presents the effects of the asymmetrical soil stiffness in the vertical plane on the response of buried pipelines subjected to two different patterns of transverse vertical PGD (Step and Block) patterns. Using the nonlinear beam-spring finite-element modelling technique in Abaqus, the analysis is conducted for an NPS 42 X70 pipe with a uniform wall thickness of 14.3 mm buried in four different types of soil and subjected to a PGD magnitude of 3.0 m. The pipeline is internally pressurized to the maximum operating pressure of 9.93 MPa and temperature variation of 50°C. The results show a significant variation in the strain demand of buried pipelines subjected to the Step PGD pattern due to the asymmetric soil stiffnesses in the vertical direction. Not only the ratio of upward and downward soil resistances but also their values affect the strain demand of the pipeline against the Step pattern.

Los Angeles Metro Rail system includes an expanding underground transportation network with over 20 mi of subway in service and another 10 mi currently in construction. An extensively monitored exploratory shaft was excavated in tar-impacted soils next to a future Los Angeles Metro station to assess the excavation performance and associated ground deformations in tar soils. The exploratory shaft was excavated to dimensions of 5.5 m in width, 11 m in length, and 22.6 m in depth. It served as a “small-scale” test bed for the future, full-size Metro station that was approximately 15 m wide, 360 m long, and 23 m deep. Data from inclinometers, surface settlement markers, piezometers, and strain gauges provided in situ performance indicators during and after the shaft excavation. Maximum lateral movement of 24.8 mm was recorded near the mid-span of the excavation, equivalent to about 0.1% of the excavation depth. Two-dimensional numerical modeling, using the software package PLAXIS, was performed to simulate the excavation performance during various construction stages at the excavation mid-span. The simulations were performed with linear elastic (LE) and hardening soil (HS) constitutive soil models using parameters estimated from in situ and laboratory testing. The HS model predicted lateral movements that compared favorably with the measured in situ wall deformations.

This study identified a statistical correlation between rutting evolution and subgrade strength, based on which a minimum acceptable subgrade strength expressed in terms of California Bearing Ratio (CBR) value was proposed. Weak subgrade condition can cause excessive rutting, which is a major type of distress in flexible pavements. Hence, a minimum subgrade strength is required to prevent unacceptable pavement rutting. The data used in this study were selected from pavements located in seven counties in Kansas. Dynamic Cone Penetrometer (DCP) tests were performed in the subgrade of selected pavement locations. Corresponding CBR values were obtained from DCP using an empirical correlation. In the statistical model, the correlated CBR was used as independent variable and average change in rutting was used as a dependent variable. Statistically significant correlation with 0.001 significance level was observed between the CBR and rut development in the pavement. Finally, a criterion for selecting the minimum acceptable CBR of subgrade was proposed.

A literature review reveals timing of soil-cement construction activities, while considered for decades, is an opportunity for improvement. Companion work recommended changes to AASHTO T134 Standard Method of Test for Moisture-Density Relations of Soil-Cement Mixtures and the objective of this paper is to supplement those efforts by performing physicochemical and microstructural testing on the same mixtures to further evaluate timing implications of soil-cement compaction sequences. Some soil-cement combinations lose meaningful density when compaction is delayed (even within what would often be considered acceptable time windows), while others do not. Generally speaking, this paper showed that soil with low cation exchange capacity, low-aluminum levels, low-clay content, and high-silicon content were least susceptible to compaction delay. The paper also showed that the recommended changes to AASHTO T134 that are based on Proctor testing were more likely to be effective than physiochemical or microstructural testing for capturing compaction delay.

In January 2020, the Minnesota Department of Transportation (MnDOT) launched a project to build a seismic system that one can routinely use in the field for quality management of Hot Mix Asphalt (HMA) pavement. The system measures the shear-wave velocity (Vs) and thickness of the pavement. When fully completed, it will be a 2D receiver-array system consisting of four (4) 1D arrays arranged transversely to measure a certain width of pavement with a high-spatial resolution (e.g., 2 ft × 1 ft). The system can be easily harnessed on a bicycle rack on the back of a car, which can travel at a speed of 10–30 MPH making rolling measurements. The on-board GPS and IR sensors record the location and temperature data for geo-referencing and temperature-referencing of the final results. The on-board software package analyzes incoming data in a fully automated mode to display results on a computer screen almost in real time. At the time of paper preparation, building and testing of the 1D 16-channel MEMS microphone array system has been completed. It includes a rolling impact source, recording device, and the on-board software package. The field test performed along a 1.2-km HMA road produced highly reasonable Vs and H values.

Longitudinal cracks develop on roads constructed on expansive subgrade soils. For several decades, state DOTs in the US have used geosynthetic reinforcement to mitigate the environmentally incited longitudinal cracks. However, only a small amount of field data has been collected to date to understand the reinforcing mechanism. Recently, the virtual load method (VLM) has been developed to identify expansive soil-induced stresses in the geosynthetic-reinforced pavement. This research integrates the VLM in the study on a low-volume rural hot mix asphalt road in Texas to evaluate the effectiveness of the geosynthetics and different reinforcement location options within the pavement layers. The soil-geosynthetic interaction is characterized by applying the subgrade heave/shrinkage-induced reaction pressure to the ground surface, with the heave/shrinkage deformations being computed from the field-measured moisture content variations data. The optimum location of geosynthetic reinforcement is determined based on the tensile force absorption value by observing the two extreme weather conditions. The results demonstrate that the tensile force absorption increases by shifting the geosynthetics towards the bottom of the pavement and achieves the most significance when it is placed between the base layer and subgrade layer in the model.

The widespread application of geocell can be attributed to its ability to provide additional confinement to the infill material and increase the load-bearing capacity. There are limited analytical approaches available to calculate the bearing capacity of the geocell-reinforced foundation. The available methods consider the lateral earth pressure theory, which may lead to the underestimation (active condition) or overestimation (at rest condition) of the bearing capacity values. This paper presents an analytical approach to calculate the improvement in load-bearing capacity of pavement foundation systems reinforced with geocell in the base layer. The proposed method estimated the radial stresses within the base layer from the theory of elasticity, which can be used to determine the bearing capacity of the unpaved road section. The proposed method yielded the most accurate results when the applied stress was within 50% of the ultimate stress.

Seasonal variation introduces modulus alteration for pavement in cold region. With the onset of freezing, the pavement gains strength with the formation of ice while the opposite occurs when spring thawing takes place. As the literature asserts the layers below the zone of freezing show very little seasonal weakening, the freezing depth is of most importance for better understanding of the seasonal behavior of pavements. To better comprehend the subgrade behavior in different seasons, instrumentation was carried out in pavement subgrade in Central New York. Moisture and temperature sensors were installed up to different depths to record the real-time change of the variables with time. In addition, installed weather station provided the climatic data. Moisture variation from 0.14 m³/m³ to 0.40 m³/m³ was observed at different depths of the instrumentation from 0.31 m to 1.21 m (1 ft to 4 ft). In addition, the temperature variation exhibited a sinusoidal pattern with the peak in July and lowest in March. With the response of climate change in Northeast part, it produced a warmer 2019–2020 and 2020–2021 winter seasons. As a result, the installed sensors recorded all above zero ground temperature during the monitoring period. Preliminary seasonal models were generated using the two years monitoring data. Long-term monitoring will further reveal the true behavior of the subgrade soil with response to climatic loading.

The aggregate base course is an important structural component of a pavement structure. Previous studies have found that there is a trade-off between permeability and structural stability of unbound aggregate base courses used in road construction. The objective of this study was to evaluate a road base material commonly used in Virginia (i.e., 21A), and to optimize its permeability and stiffness by varying the percentage of fines (from 0% to 10%), changing the sand content, and blending with different quantities of No. 57 stone, an open-graded aggregate. The permeability was measured by the falling head or constant head laboratory methods. The blended aggregates were also tested for resilient modulus and shear resistance. This paper presents the results of the permeability, stiffness, and strength tests. It also illustrates the importance of the time-to-drain of 50% drainage level (t₅₀) and discusses its implication within the context of current pavement design practices.

Behavior of expansive subgrade is influenced by the role of temperature variation with time. Temperature gradients can generate moisture flow in subgrade which ultimately results in variation of shear strength and hydraulic conductivity. While experimental set up have asserted the weakening of clay with increasing temperature, distressed field performance is also observed with temperature variation. In the case of low-volume load, especially, the asphaltic layer, whose stiffness decreases with increasing temperature, serves more as a surface seal than as the main load carrying component. As such, the behavior of the subgrade layer in response to temperature variation is of great interest. Accurate measurements of soil temperature can be obtained through soil sampling and testing; however, this process can be extensive and costly. Thus, developing models that can accurately predict the temperature profile in an expansive subgrade becomes of great interest. The objective of the current study is to develop temperature models using real-time field monitoring data from hot mix asphalt roads in North Texas. Subgrade soils were instrumented using temperature sensors up to various depths. The results obtained from this study produced a temperature prediction model that was dependent on depth and day of the year. The squared correlation coefficient between the observed and predicted soil temperature was around 0.70. Application of the developed models could allow for noninvasive estimation of the response of soil strength and stiffness properties due to variations in temperature.

Modulus or stiffness of granular layers is a fundamental material property needed for pavement analysis and design and is also used as a quality control indicator of a constructed pavement layer. This paper presents results from a laboratory study on repeated load triaxial tests with bender elements (BE) to compare the modulus properties of base, subbase, and subgrade materials in small and resilient strain levels. Three pavement base course aggregate materials and one silty-sand subgrade soil were selected to prepare specimens at target maximum densities and optimum moisture contents. BE pairs were installed at different heights in the specimens to collect shear-wave velocity data. In addition, a pair of piezoelectric disk elements was installed in the subgrade sample to collect the compressional wave velocity. Repeated load triaxial testing was performed following the AASHTO T 307 resilient modulus test procedure. From the 15 loading stages at different stress states, the shear-wave velocities, and compressional-wave velocity (when applicable), the resilient modulus properties were evaluated at the end of each stress state. Comparisons were made among modulus values obtained in different strain ranges such that shear-wave velocities measured by BE were utilized to calculate the modulus in a small-strain range, while the resilient modulus in a larger strain range was estimated by strain measurements. The test results regress to a linear relationship between small-strain elastic modulus and resilient modulus for crushed stone coarse aggregates and silty-sand subgrade soils. The findings of this research prove the possibility of establishing correlations to obtain the resilient modulus of granular materials from BE measurements at smaller strains and enable the utilization of the small-strain modulus measured in situ and instantaneously by BE sensors for pavement analysis and design purposes.

A “Smart Runway” project was recently undertaken in Utah through the efforts of the Engineer Research and Development Center (ERDC) of the US Army Corps of Engineers to install advanced sensors into a runway pavement test section and monitor pavement responses and damage accumulation over time due to trafficking with critical aircraft systems. In support of the “Smart Runway” project, laboratory tests were conducted on the subgrade, subbase, and base materials obtained from the Hill Air Force Base (AFB) runway pavement, including grain size distribution, image-based shape analysis, anisotropic resilient modulus tests using an innovative UIUC-FastCell test device, and triaxial shear strength tests. In this paper, the laboratory characterization test results are presented and utilized to verify the field response measurements as obtained from Bender Element (BE) shear-wave transducers and Heavy Weight Deflectometer (HWD) tests. A linkage was established between laboratory and field-testing results through advanced testing, materials characterization, and analysis approaches.

Surficial distresses in roadways of Texas are very common due to presence of high-plastic clayey soil in the subgrade. The high sensitivity of such soils towards seasonal moisture changes results in repeated swelling and shrinkage, and ultimately the development of pavement cracks. Studies have indicated rainwater intrusion into underlying expansive subgrade soil coupled with inadequate drainage as the main cause of pavement damage in semi-arid regions. As such, inclusion of an appropriate moisture control mechanism either during the initial construction of new pavement or during rehabilitation of existing distressed pavement can be an effective tool in enhancing the service life of pavements. This paper presents the evaluation of modified moisture barrier (MMB), a recently introduced moisture control mechanism in pavement structure, through field implementation. MMB was installed throughout the full width of a 91 m (300 ft) long distressed pavement section in a farm to market road with the aim of preventing potential moisture intrusion from the pavement’s surface and controlling the differential movement of the subgrade soil that may propagate to the surface over time. Based on field instrumented sensors and inclinometer readings, the utilized barrier system was effective in maintaining equilibrium moisture content of expansive subgrade soil and minimizing the subgrade’s movement by 89% despite seasonal wet-dry cycles.

Georgia Institute of Technology’s (Georgia Tech’s) response to the COVID-19 pandemic included ensuring students gained equitable exposure to hands-on learning. Instructors of the introductory geotechnical engineering lab course developed At-Home Lab Kits that contained materials for students to gather data at home to learn different geotechnical engineering concepts. An end-of-semester survey was distributed for students to share their experiences and for instructors to observe the effectiveness of the virtual lab instruction method. Overall, 90.5% of students responded that labs with hands-on tests were more beneficial than labs that only involved data analysis. Among the topics presented, students were most confident in their understanding of grain size distribution and hydraulic conductivity; they were least confident in their understanding of Atterberg limits, the only instruction topic that did not include hands-on experimentation. Results indicate that at-home lab experiments are a beneficial substitution for in-class lab procedures when in a virtual pedagogy.

Geotechnical engineering subjects can be perceived by some students as difficult when proper teaching methods are not used. This may be due to the fact that soil and rocks are complex, heterogeneous materials, and geotechnical design involves significant uncertainties. Prior research works indicate that it is important to demonstrate the social relevance of the topic and its interesting applications. This study aims to develop diverse hands-on activities to attract high school students into the field of geotechnical engineering. The team developed a class module to introduce local high school students to the fundamental concept of and various applications in the field of geotechnical engineering. To further demonstrate geotechnical concepts, four in-class hands-on activities were designed, covering topics, such as coastal erosion, soil reinforcement, earth retaining wall, and soil liquefaction. These activities used simple materials that are easy to implement in a regular classroom setting. Survey questions were designed to collect feedback from students and teachers to help further improve these hands-on activities and class module. Through the development and implementation of such geotechnical engineering activities, this study aims to increase students’ interests in learning geotechnical engineering topics and attract more students into the field of geotechnical engineering.

This paper presents a novel laboratory experiment that can be incorporated into introductory soil mechanics courses to introduce students to the field of biogeotechnical engineering and the use of biostimulated microbially induced calcite precipitation (MICP). Applying MICP to granular soils results in an increase in peak strength and shear stiffness of the soil as a result of the precipitation of calcium carbonate on soil particle surfaces and at soil particle contacts. The authors developed protocols to treat small volumes of soil and to test the effectiveness of the treatment using a simple strength test based on ASTM D3967-16. In fall 2020, the experiment was piloted as a four-week, course-based research experience that can be conducted by students remotely or in a traditional laboratory environment. This paper provides an introduction to MICP and describes the protocols for conducting the experiment. The paper also suggests approaches for how the experiment can be incorporated into a traditional introductory soil mechanics course.

The National Science Foundation funded the Geotechnical Women Faculty (GTWF) Project in 2016 to promote gender parity amongst geotechnical engineering professors in the United States. The GTWF Project has, as part of its efforts, built a database of tenured and tenure-track faculty. This database was first created in 2016 at the start of the GTWF project, and recently updated by the team in 2021. The results are “snapshots” of the field at two points in time (2016 and 2021) that can then be compared to assess the effects of initiatives to increase the field’s gender diversity. The data also allow the status of US-based female faculty in the geotechnical field specifically to be compared to broader trends in Civil Engineering as a whole. Further, data are presented regarding inclusion in the field of geotechnical engineering through a look at female faculty’s share of ASCE awards, committee chairs, and university distinguished lecture series. Initial results show that the field of geotechnical engineering still lags behind when compared to civil engineering as a whole, and that placement of women in tenure-track faculty positions has grown only slightly since 2016. Participation data paints a picture of a field starting to see the recognition of women in the field, with female faculty receiving a higher percentage of awards for those under 35, and increasing numbers of female tenure-tracked faculty. These data indicate that efforts over the past decade to increase gender parity are meeting with real-world impact that has seen the field add female faculty at a rate well above the average for Civil Engineering as a whole, but that more now needs to be done to support women’s recognition and inclusion in the field. A follow-up survey in 2025 is also proposed to further assess the changing state of the field.

Monosoil is a virtual board game inspired by the well-known game Monopoly. Players compete with each other by answering questions related to the basic concepts of soil mechanics. The questions cover a wide range of topics, from theoretical concepts to laboratory tests. The game has been developed via MATLAB GUI, allowing players to experience an interactive learning session. The game aims to familiarize senior civil engineering students with soil mechanics by introducing the essentials of the field while enjoying the competition. The entertaining features such as the bonuses and penalties of the regular board games are embedded into the game to preserve players’ attention throughout the game. The game constitutes supplementary materials for educational institutions to utilize digital sources during the COVID-19 pandemic. The game offers a fun way to learn soil mechanics concepts for students. Questions can be easily updated without manipulating the codes. In this way, a flexible and adjustable teaching experience is offered to educational professionals. Therefore, the game can be adapted to any undergraduate or graduate geotechnical engineering course.

In this study, the Atterberg limits tests (ASTM D4318 Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils) are visualized by creating a game that presents a virtual soil lab environment via MATLAB App Designer. The environment consists of a graphical user interface (GUI), allowing students to gain hands-on experience on the test. In this environment, a specimen can be prepared by adding water to soils, then placed into a virtual Casagrande apparatus enhanced by animations and sound effects. After that, a groove tool is used, and the apparatus is operated as if it was used in reality. The number of drops is counted to obtain the liquid limit of the soil. While performing these procedures, the virtual laboratory automatically generates some soil properties with randomized features, focusing solely on the processes rather than the measurements and calculations. Moreover, continuous feedback is provided, such as the rotation speed or the suitability of the different specimens with distinct water contents. In determining the plastic limit, kneading and rolling actions are driven by mouse clicks. The plastic limit is obtained after the roll is crumbled. The soil is then classified according to the Unified Soil Classification System (USCS) plasticity chart. With its randomized nature, the game aims to create a realistic laboratory experience. The game is inspired by the COVID-19 pandemic, which prevents most students from joining laboratory sessions essential for understanding experimental soil mechanics. The authors believe that this game will allow students to perform each step of an experiment, which sometimes cannot be achieved in laboratories due to time constraints. In addition, the game will likely engage students to a commonly performed soil mechanics test by pre-test quizzes, feedback, and visualizing features. With the advances in computer technology, this game offers a strengthened learning experience interactively.

It has been well established that recall questions result in learning gains for students. In this context, this paper addresses the following question: Is it possible that teachers too have something to learn from the use of recall questions in instruction? To answer this question, the following hypothesis was formulated: “It may be possible, if the recall questions admit answers that can detect nuances in student understanding”. The hypothesis was tested by phrasing such answers to questions accompanying an existing online video lesson on “what happens when soil compresses” and offered to students of a Soil Mechanics course as optional homework assignment. The answers of the students indicated which questions cannot detect nuances in student understanding (all students answered them correctly) and which produced varied student answers. Most of the questions belonged in the second kind and revealed or confirmed students’ misunderstandings, thus helping the instructor learn about how students themselves perceive the material.

The abrupt shift to a primarily remote environment for higher education learning due to the COVID-19 pandemic left many academic institutions unprepared to provide students with the quality of education traditionally expected in an in-person modality. Students were deprived of the hands-on activities and shared experiences of in-person learning that increase engagement, learning, and the overall educational experience that students rely on to grow as people and engineers. The lab-based nature of Geo-Education has rendered it particularly susceptible to this issue. New tools capable of bringing hands-on learning to remote students and an instructional focus on promoting shared experiences in this new era of learning are essential for the continued development of students in higher education through the COVID-19 pandemic and other future disruptions. The GeoExplorer CPT Operator module is a mixed reality environment that was adopted for remote implementations in the Spring 2020, Fall 2020, and Spring 2021 semesters. Originally developed to advance and equalize how undergraduate civil engineering students obtain geotechnical field experience, GeoExplorer gave in-person and remote students the opportunity to simulate hands-on learning when most other opportunities for this style of learning were impossible. This mixed reality platform was presented to students in the same modality as laboratory experiments for which students would typically go into the physical laboratory space in the Spring 2021 semester, which is the focus of this paper. The difference between students interacting with this platform and other shared experience interventions when in-person versus remote was leveraged to assess the ability of these strategies to augment or fully replace hands-on experiences. Mixed methods data acquired through surveys, intermediate quizzes, laboratory reports, and interviews show the benefit of using mixed reality platforms in remote learning with respect to both engagement and learning gains. This research found that there was a difference in grades between remote and in-person students, and that there are new approaches to instruction and shared experience strategies that can help equalize the experience for in-person and remote learning. This attempt at equalization may be what carries students through times of future disruption to higher education.

Enhanced geotechnical engineering education at the undergraduate level is of great significance in motivating students to pursue their career in geotechnical engineering. The decreasing number of students with geotechnical engineering interest is of concern to the growth of the geotechnical engineering profession. Many students lose interest for fear of rigorous laboratory work, poor lecture planning, and delivery modes. The use of innovative pedagogical approaches can help reverse this trend, as it will reduce learning gaps and lead to deeper learning experience. For this reason, a new pedagogy which recognizes the learning trends of students has been developed as a blended online teaching approach. The approach is based on a modified version of the co-operative hands-on, active, problem-based learning (CHAPL) and the discover, learn, practice, collaborate, and assess (DLPCA), pedagogies. The approach encompasses an array of learning styles and fits into a broad range of students. The new pedagogy CACPLA (communicate, active, collaborate, problem-based, learning, and assess), is relatively easy to adopt to the conventional geotechnical engineering coursework. We adopted the CACPLA method to a typical geotechnical design of a foundation course to fourth year civil engineering students at the Ahmadu Bello University, Zaria, Nigeria, to experiment on the students learning outcomes. We hypothesize that using the CACPLA pedagogy for lecture delivery, instructors can increase the enthusiasm of students in geotechnical engineering education.

Earth and rock-filled gabions have valuable applications in engineered dams, walls, and foundations, as well as for erosion control and military force protection. A gabion mattress, also commonly known as a marine mattress, is a variation of the gabion that utilizes geosynthetic materials with a relatively small height compared to its much larger length and width dimensions. While gabion baskets and walls are typically used for slope stability, marine mattresses are primarily used to protect against erosion and wave action along slopes. While uplift stability and down-slope sliding are two concerns to be mitigated when incorporating a marine mattress into designs, the presence of a marine mattress on a slope affects the underlying slope’s stability. Slope stability analyses are essential for design of sloped applications of marine mattresses, particularly on soft soils, and the ability to accurately set up analysis software to aid in geotechnical design is crucial in making sound engineering recommendations. While there is some information in the literature regarding slope stability regarding gabion boxes baskets and walls, as well as geosynthetics and revetment stone layers along slopes, there is limited information on modelling revetment stone filled geosynthetic gabion mattresses along a slope. In their recent 2021 software update, the limit equilibrium software used in performing the analysis introduced a reinforcement library to choose specific manufactured geosynthetic products. This consists of a limited selection of products from two manufacturers. While geogrids are not included, a marine mattress was not included in the updated version. In this study, the stability of a partially submerged marine mattress was analyzed in five potential ways including modelling as (1) a high-strength material, (2) an unreinforced layer of revetment stone, (3) a layer of revetment stone enveloped by a geosynthetic material, (4) a layer of revetment stone enveloped by a specific manufactured geo-grid, and (5) a surcharge load with the same unit weight as the revetment stone layer. The advantages and disadvantages of each modeling scenario are discussed, and factors of safety for global failure are compared.

Geotechnical investigations produce an enormous amount of data that is extremely valuable to the geotechnical engineering and construction communities. Data analysis and data visualization are needed to communicate data in meaningful ways. They are also needed to understand the challenges of organizations that collect and/or use geotechnical data. Microsoft’s interactive data analytics and visualization platform for business intelligence is known as Power BI. In this paper, we will show how we helped our clients use Power BI on various projects to evaluate geotechnical data, compare different parameters of available data, and assess overall project success.

This paper presents a cyberinfrastructure (i.e., web-based platform) for geotechnical engineering for storing, computing, and managing capabilities of project data, analyses, and designs. This geotechnical engineering cyberinfrastructure (GTCI) hosts basic project data, analysis packages, and design results. GTCI consists of (1) a web portal enclosing the details of computation and data management, thereby minimizing the required learning effort, (2) a flexible framework that allows easy extension by integrating geotechnical analysis suites for analysis and visualization; this means users can add new tools/scripts as needed overtime, and (3) a common repository to manage data and results through a database that maintains metadata. Furthermore, in GTCI, all design data, models, and results live online, offering the ability to submit, review, exchange, and edit designs. GTCI, therefore, overcomes the status quo of relying on offline segregated data, analyses, and designs. Thus, GTCI increases the security, safety, and lifetime of critical project information.

Errata identify incorrectly published items and technical errors. This file contains errata that shall be used from their effective dates; the most recent effective date is 03 30 2022.