Geo-Congress 2024: Geotechnical Site and Soil Characterization

Retention rate refers to the content of soil remaining in the dumped area compared to the left sample during dredged soil dumping. During reclamation construction, the retention rate calculates the amount of dredged soil, so it is essential to determine the exact retention rate. The retention rate may be calculated differently depending on the soil characteristics, but currently, in the case of dredging and reclamation on the West Coast, the retention rate is empirically applied at 70%–95%, or the amount of dredged soil is calculated through examples of application of retention rates in similar districts nearby. Accordingly, in this study, to accurately calculate the retention rate, a separate sedimentation model test was conducted using dredged soil at the location where the actual project was carried out. Separated sedimentation characteristics were confirmed through mechanical and physical tests for each deposition distance, and the retention rate was calculated to be 89.0%, which is relatively higher than the literature and existing cases. This study was used as primary data to confirm the feasibility of the road construction project connecting the Saemangeum area to the north and south.

This paper presents a methodology for analyzing the uncertainties of uniaxial compressive strength (UCS) test data for metamorphic rocks based on statistical and mineralogical analyses. The methodology consists of three steps: data treatment process, schistosity angle, and mineralogy. The treatment process involved different data treatment techniques to assess the variabilities of UCS data, and to determine appropriate outlier detection methods based on multiple decision-making criteria and engineering judgment. The results showed that adjusted boxplot and 2SD method provided more accurate outcomes in detecting outliers. The findings reveal that traditional boxplot may not be the best for treating UCS data. Moreover, the study examined the impact of schistosity angle and suggests removing samples within a specific angle range to decrease UCS variabilities. The mineralogical analysis examined the impact of various minerals on UCS variations, revealing a correlation between the dispersion and the variabilities of both hard and soft minerals.

Earthquakes are a worldwide natural disaster that can happen without warning. Earthquakes not only cause devastation to infrastructure but also change the soil characteristics. Recent large-scale magnitude earthquakes in the Gyeongju and Pohang regions of Korea led to soil liquefaction. To prevent damage in urban areas, it is crucial to predict and assess earthquake risk by deeply analyzing the geophysical properties in earthquake-prone areas. The dynamic properties of soil (e.g., P-wave velocity, S-wave velocity, and wave attenuation) are important parameters for analyzing seismic activities. It is important to build a unified database by collecting dispersed geophysical data for characteristic assessment of such regions. One of the important factors to reflect the seismic response spectrum of earthquake-prone regions is elastic wave velocities, which should undergo a detailed analysis. A database was established in this study by collecting data from 700 boreholes over two years in the Gyeongju and Pohang regions of Korea, including geospatial information (e.g., coordinates of borehole and depth of bedrock), dynamic properties (e.g., P-wave velocity and S-wave velocity), and physical properties (e.g., N-value and permeability). The geotechnical characteristics of the Gyeongju and Pohang regions in Korea were analyzed using an established database. The elastic wave velocities in these regions were predicted using machine learning. This research highlights the importance of analysis of the characteristics of earthquake-prone areas, Gyeongju and Pohang regions of Korea, using machine learning, and it will contribute to the earthquake risk prediction and assessment.

Mapped landslide databases and estimates of the seasonal groundwater conditions provide an opportunity to back-calculate statistical distributions of macroscopic geologic deposit strengths. Based on the general assumption that landslides are most often active, with their strength fully mobilized, within existing landslide deposits during wet conditions, we develop a maximum a posteriori inversion method to back-calculate strengths for various geologic deposits. In this method, multiple landslide modes are evaluated for dry and wet conditions, and the factor of safety is computed for a wide range of deposit strengths and landslide geometries. The optimal strength parameters (1) plausibly represent the available laboratory and field index test data while also producing a distribution of landslides that (2) best matches the landslide inventory maps during wet conditions and (3) minimizes overprediction of landslides during dry conditions. The resulting strength estimates are more appropriate to evaluate a broad set of landslide failure modes than estimates from previous studies, which often rely on sparse laboratory strength data or inversion from a single mode of failure. We demonstrate the applicability of the back-calculated strengths in a test area of the northern Santa Cruz Mountains of California, USA, for M6.9 Loma Prieta and M7.9 San Francisco earthquake scenarios.

Secondary geologic features, such as fissures, greatly influence soil physical properties and mechanical behavior. Because laboratory element-scale experiments often fail to capture these features due to the small specimen size, in situ tests such as the cone penetration test (CPT) often are used to characterize potentially fissured soil under in situ conditions. However, current CPT-based soil characterization charts lack information on the secondary fabric of soil. To address this, this study applies the zero-mean weakly stationary random-field model to assess inherent soil variability with respect to CPT parameters, including corrected cone resistance (q_t), sleeve friction (f_s), and penetration-induced pore pressure (u₂). Results show that intact clays exhibit a scale of fluctuation (δ) value (an indicator of the range of correlated domains) about three times larger than fissured clays for all three CPT parameters, with a value of 0.45 m separating the two categories. The study concludes that q_t is the optimal parameter for evaluating fissures, and the procedures outlined can be used to differentiate fissured and intact clays at other sites.

The significant advancement in the production of crude oil and natural gas through hydraulic fracturing and directional drilling has transformed the energy landscape in the US but has also led to increases in waste generation. Waste generated from exploration and production (E&P) of oil, gas, and geothermal energy is often referred to as E&P waste. Many US state governments have specific regulations and guidance for proper management and disposal of E&P waste, including adequate characterization of the physical properties of the waste. This paper focuses on the geotechnical characterization and behavior of in-place E&P waste derived from solid and semi-solid portion of drilling (i.e., drilling muds and cuttings) and disposed of at a landfill site in southern US. Results of the geotechnical site investigation suggest that, based on the site-specific pre-processing and placement technique, the in-place E&P waste classifies as a medium stiff, lean clay with relatively low permeability. Based on the comparison of laboratory test results with well-established cone penetrometer testing (CPT) correlations, the CPT was found to be an excellent tool for characterizing the E&P waste.

This paper presents a laboratory investigation to understand the mechanical and deformation behaviors of Wyoming shales. Seven shale samples were collected from different locations in Wyoming, including different formations, geologic ages, and depths. Thirty-three specimens from seven samples were prepared for a series of uniaxial and triaxial compression tests. In addition, porosity and specific gravity tests were conducted on these cylindrical specimens. Using historical and recently completed test data, regression analyses were performed to establish prediction equations to relate uniaxial compressive strength (UCS), peak compressive strength Young’s modulus (E), and shear strength parameters to physical properties. Some of the conclusions are: (1) UCS decreases with the increase in moisture content and porosity, (2) E increases with the decrease in moisture content and porosity, and (3) cohesion decreases with the increase in porosity. These recommendations are developed to facilitate the design and construction of transportation infrastructure in Wyoming.

Understanding the physical and mechanical properties of the lunar regolith is critical for various human operations to establish a permanent presence on the Moon. In this paper, an experimental test bed was designed and constructed to simulate the process of drilling into lunar regolith simulants. The developed test bed is composed of a loading frame, linear motion assembly, sliding plate, rotary drilling tool, cylindrical regolith container, and Plexiglass protector. The test bed is adaptable for drilling experiments with different shapes and configurations of drilling bits. The test bed is employed to study the mechanical responses of lunar regolith simulants during the drilling process, and the preliminary results for the tip and friction resistance along the depth are obtained. The test bed provides a useful experimental setup for future endeavors to develop new drilling tools to characterize the in situ properties of lunar regolith.

The direction-dependent behavior of soil was investigated by controlling the inclination of major principal strain axis (α_ε) and intermediate principal strain parameter (b_ε). The data acquisition and control (DAC) program used in the Carleton University hollow cylinder torsional shear (HCT) apparatus was modified to enable testing along prescribed three-dimensional strain paths. This paper predominantly focuses on the testing procedures and intricacies involved in conducting the complex generalized strain path tests. Preliminary test data obtained from isotropically consolidated Fraser River sand specimens, sheared along strain paths with different inclinations of major principal strain axis is presented. The hardening tendency of the sand systematically decreases when the direction of major principal strain changes from the direction of deposition to direction of bedding, ceteris paribus. The friction angle at phase transformation is found to be essentially unique and independent of initial stress states and strain paths.

This paper presents a numerical study into the competing influences of creep and pore pressure dissipation (diffusion) on the shear resistance of a stratum of saturated clay. The analyses comprised fully coupled mechanical-flow simulations using the user-defined viscoplastic constitutive model PM4SiltR in the finite difference program FLAC 8.1. Simulations were performed for a single soil layer under infinite slope loading conditions (analogous to simple shear loading). A target shear stress was imposed under undrained conditions, after which pore pressure diffusion was initiated while the target shear stress was maintained constant. Analysis results illustrate the competing influences of consolidation and creep on the pore pressures at different depths within the clay layer. Results are presented for cases that do and do not lead to undrained creep rupture. A framework that relates rate of consolidation characteristics and sustained static shear stress levels to the potential for creep failure is presented. The practical implications of the results are discussed.

Most geotechnical engineering problems involving cyclic loading require measurement of dynamic soil properties, that is, shear modulus and damping ratio. Measuring the damping ratio is a quantitative approach to incorporating energy dissipation or attenuation of waves propagating through a soil mass by induced cyclic excitation. The importance of the damping ratio is primarily appreciated in ground response analysis in earthquake engineering and soil-structure interaction analysis under seismic or cyclic loading in structural and geotechnical engineering. The damping ratio, attributed to the energy loss in a soil mass under cyclic loadings, such as that generated by earthquake activity, can be calculated based on laboratory tests such as resonant columns and cyclic simple shear devices. Measuring damping ratios in the laboratory allows the investigation of the effect of boundary conditions, such as temperature, on the damping ratio of the soil. The impact of various parameters, such as the plasticity index, stress history, confining pressure, strain amplitude, device effect, and soil sampling, on the dynamic parameters of soil has been addressed in the literature. However, the impact of rising temperature, a growing concern in geotechnical and structural engineering, requires far more investigation and constitutes the main motivation for the present work. Thermo-controlled resonant column (RC) tests were performed on three cohesive soil samples with different moisture contents. The damping ratios were calculated using the half-power bandwidth (HPBW) and the free-vibration logarithmic decay curve (LDC) methods. Regardless of the measurement method, the damping ratio values are expected to be identical; however, obtaining a unique damping ratio for the test soils is challenging experimentally. The results showed how changes in the water content could affect the attenuation of the energy in the cohesive materials under thermo-cyclic loadings.

Soft rocks and cemented sands are ubiquitous in nature, and the mechanical response of such non-textbook soils has been extensively studied through experiments and discrete element modeling. The amount of cementation significantly influences the overall mechanical response. Depending on the amount of cementation, cemented sands can be classified into contact bound or void bound cemented sands. In this study, a micro mechanical study of cemented sands is carried out inside the X-ray computed tomography (XRCT), during one-dimensional compression. The kinematics of cemented quartz ensembles are examined with measures such as particle-scale rotations and displacements from the high-resolution XRCT scans. The differences and similarities in particle size distributions, coordination numbers, void ratios, particle displacement fields, cement disintegration, etc., in the contact and void-bound cemented sands are studied. Specifically, the quantification of the cementation present at the contacts or voids and its evolution with loading is presented here. The results obtained from the study indicate that the void-bound specimen has significantly higher stiffness than the contact-bound specimen and undergoes lesser cement disintegration. These results are critical for a multiple-length scale understanding of the behavior of cemented sands and benchmarking of constitutive models.

The influence of effective confining pressure on Chang Dam soil obtained from the Kutch region in India is explored in a flexible boundary plane strain apparatus. The boundaries of the apparatus were relatively flexible along the two loading directions. The test set-up offers the advantage of measurement of strains and stresses along the principal loading and lateral direction. Consolidated undrained tests were performed for sand at four effective confining pressures. The applicability of instability criteria based on the second-order work is examined for Chang Dam soil. Furthermore, the instability onset indicated by the evolution of lateral strains is almost coincident with the second-order work criterion. However, the global stress-strain response does not depict unstable behaviour. The dilatancy angle decreases non-linearly with the stress ratio. The stress ratio at phase transformation is observed to be a function of the state with varying effective confining pressures.

Louisiana’s barrier islands have been experiencing high rates of land loss during the last decade. Therefore, coastal restoration efforts have increased to combat land loss. Buried paleo-river channels are suitable sand sources for restoration because of their location and complex buried network of available material. Excavated borrow pits in paleo-river channels are referred to as mud-capped dredge pits or MCDPs. However, the use of these paleo-river channels is limited by the setback distance, which is currently set to be 1,000 ft. Therefore, this study aims to investigate the geotechnical properties of the MCDPs at two locations in the northern Gulf of Mexico (Raccoon Island and Peveto Channel), where these data could be used to examine the stability of the pit-wall. Vibracores were collected inside and outside MCDPs to study their shear strength and index properties. The torsional ring shear device was used to find the peak and residual shear strength under various effective stress and displacement rates. The results showed that the sediment outside the pit has higher shear strength than inside the pit in the two MCDPs. This study will provide a better understanding of the MCDPs behavior and provide insights into minimizing setback distance, which will reduce dredging costs and allow using the sand source more effectively in the northern Gulf of Mexico.

A new testing system for determining soil particle size distributions (PSDs) is under development. It augments existing systems generically called “SedImaging” by the addition of a water pressure transducer near the bottom of a soil sedimentation column. The original SedImaging test provides image-based PSDs for sands, while the pressure transducer will extend the PSDs into the silt range. The new test system is called the “uSed” reflecting the measurement of water pressures (u) during a SedImaging test. This paper presents the uSed theoretical equations and the results of four pilot tests on sands to verify the theory. The four specimens were coarse sand, medium-sized sand, fine sand, and a gap-graded sand. The observed pressure decay curves were qualitatively as expected and the masses of solids predicted by the uSed theory agreed with the actual specimen masses to within an error of 2%.

The potential connection of stress diffusivity to anisotropy is explored. The approach taken in this investigation is empirical. It is postulated that material (microstructural) anisotropy would affect stress distribution given by the diffusion theory in ways analogous to what is observed in elastic anisotropy solutions; that is, it modifies attenuation with depth and lateral distribution in similar ways. A case example of a horizontal layer, with two-dimensional geometry, subjected to a uniform strip load, is analyzed using both stress diffusion and anisotropic elasticity theories, and correlations between the resulting stress fields are observed over a range of stress diffusivity coefficients and anisotropy ratios. A strong empirical relationship is found to relate the two parameters; the diffusivity coefficient increases with increasing anisotropy ratio. Overall, the study confirms that anisotropy is a factor in stress diffusion and contributes to a better understanding of the meaning and assessment of the diffusivity coefficient.

Hydraulic fracturing is mainly used in tight gas reservoirs with low permeability such as shale, limestone, and some coal beds. It is a process in which a mixture of water, chemicals, and proppants is injected under high pressure through a well to create new fractures and/or expand the existing fractures for enhanced connectivity and oil recovery. The closure stress of rocks leads to crushing the proppants decreasing their permeability and shear strength. This paper presents some of the findings from a series of experimental investigations to evaluate the crushing resistance of different types of proppants under high closure stresses. The stress–strain response, the breakage behavior, and the change in particle size distribution were measured. Moreover, the effect of crushing on the single-grain proppant particle was studied, including proppants’ characteristic strength, the failure load, and Young’s modulus. Additionally, the change of the permeability and shear strength due to the crushing of the proppants were measured. The results confirmed that choosing an appropriate proppant type based on the nature of the reservoir formation is critical in quantifying the degree of proppant crushing.

As increasing amounts of sand are added to a gravel, the soil mixture transitions from gravel to sandy gravel to gravelly sand and eventually to sand. This change in soil composition leads to changes in the maximum and minimum index void ratios (e_max and e_min) of the soil mixtures. In this study, correlations were developed for predicting e_max and e_min of sand-gravel mixtures. The correlations use e_max, e_min, and the median grain sizes of both the sand and the gravel as well as two empirical constants: the filling coefficient, a, and the embedment coefficient, b. Based on a laboratory testing of a series of sand and gravel mixtures, simple correlations for the parameters a and b were developed.

Glauconite is the name of a mineral and soil containing significant quantities of iron and potassium varying in color from green to black, linked to its geological history. These soils are problematic in nature and exhibit potentially hazardous responses related to the construction of foundations. This is in part due to the difficulties in quantifying their geotechnical properties and how easily these properties change. Sand-sized glauconitic particles are often fractured, which increases their crushability, transitioning from sand-sized to fine-grained particles with cohesive behavior. This has led to geotechnical challenges including difficulty in pile driving and the potential for refusal. Glauconite has been shown to adhere to pile walls, which increases pile driving resistance. This may be a problem as glauconite deposits can be found along the eastern coast of the US in offshore wind lease areas. In this study, two glauconitic sands from the East Coast of the US are investigated for differences in their Atterberg limits in their natural and crushed state to quantify the increases of plasticity. Results on samples from the Late Cretaceous Navesink and Paleogene Hornerstown formations illustrate how sample preparation and particle crushing increases plasticity and changes USCS classification of glauconite soils. Additionally, it was found that these specific soils are acidic and when crushed their acidity levels and their colors can change.

Climate change and sea level rise have the potential to significantly alter existing natural groundwater levels and pore water chemistry in soil deposits that are near the ocean. As ocean levels rise, a salinity front advances through the groundwater, and extreme events such as hurricanes or winter storms cause the introduction of saline water further inland at the surface. After a high-water event, standing surface water left in pools evaporates, leading to high-salinity water pools or salt deposits at the surface. Existing animal burrows, desiccation cracking, and plant root structures (for plants that are alive or dead) facilitate the exchange of salts and other contaminants in a complex regime. The current study describes the process of instrumentation of a natural terrestrial site to monitor seasonal variations in temperature in the soil profile, fluctuations in groundwater level, changes in soil pore pressure, and changes in soil salinity. The goal of this instrumentation program is to develop a more specific understanding of the effect of changes in salinity due to flooding and sea level rise on the physical, chemical, mechanical, and biological properties of soils. For this study, a project site was selected at the St. Jones Reserve, located along the St. Jones River and the Delaware Bay in the state of Delaware, in the USA. The site is located south of the Dover Air Force Base and is part of a roughly 700-acre sanctuary, which includes the Delaware National Estuarine Research Reserve, and the St. Jones Center for Estuarine Studies. In the field at the site, a series of instruments and data logging systems were installed along a transect that follows a salinity gradient from non-saline to saline pore water. This site has been heavily instrumented with various instruments by the current team as well as other researchers, to assess seasonal variations in temperature, pore pressure, volumetric water content, and salinity. This study will provide preliminary data from the initial monitoring stages, along with background knowledge in regard to sensor selection, fabrication of sensor arrays, and installation procedures of the data logging system for this site.

To help advance capabilities for measuring the in situ cyclic response of soils at chosen depths under controlled cyclic loading, a new prototype cyclic borehole shear test (CBST) device was developed in this study. Based on the monotonic BST device, the new CBST applies controlled normal and cyclic shear stresses to soil through serrated steel plates in contact with the wall of a 3-in. diameter borehole, while measuring the displacement of the shear plates as well as the shear stresses applied to the soil. Pore pressure is measured using a sintered porous disk embedded in one shear plate and hydraulically connected to a pressure transducer. Using the hardware and software control programs developed in this study, the capability of the prototype CBST device to measure the monotonic shear strength of soil is demonstrated, and preliminary results on the measured in situ soil behavior under cyclic loading conditions are presented.

This paper develops a rigorous solution for the undrained cylindrical cavity expansion problem in non-associated Mohr-Coulomb soil under non-hydrostatic initial stress field, that is, with moderate K₀ values of the earth pressure coefficient. The proposed novel, graphical analysis-based theoretical framework contains two essential components: the geometrical analysis to track the stress path trajectory/evolution in the deviatoric plane and a full Lagrangian formulation of both the constitutive relationship and radial equilibrium equation to analytically determine the representative soil particle responses at the cavity surface. The salient advantage/feature of the present graphical approach lies in that it can deduce the cavity expansion responses in full closed form, nevertheless being free of the limitation of the intermediacy assumption for the vertical stress and of the difficulty existing in the traditional zoning method that involves cumbersome, sequential determination of distinct Mohr-Coulomb plastic regions. The analytical solution/model is used to predict the cavity expansion responses and to investigate how the undrained cavity expansion curve and the ultimate cavity pressure are influenced by the key soil plasticity parameters and the earth pressure coefficient at rest.

Soil compaction is a critical process that enhances the strength and compressibility characteristics of geomaterials, which ultimately improves the engineering performance of earthen embankments for various civil infrastructure elements including roadway and bridge foundations and earthen embankment dams. Therefore, quality-assurance and quality control (QA/QC) processes utilized during the soil compaction process are crucial to ensure that these embankments are being constructed adequately to their specified engineering design. Traditionally within the United States, after a soil has been placed and compacted, the “end-product” of the soil compaction process is assessed using a nuclear density gauge (NDG) to infer the in-place dry unit weight and moisture content. Though these types of NDG tests are relatively nondestructive in nature and can be conducted within a timely manner, NDGs utilize radioisotopes to infer dry unit weight and moisture content. The radioactivity of these isotopes presents numerous logistical and regulatory challenges when operating, transporting, and storing these devices. In response to these challenges, a new low-activity nuclear density gauge has been developed (the “EGauge”), which utilizes a smaller, more well-shielded Cesium-137 gamma radiation source to infer moist unit weight and an electrical capacitance-based moisture probe to infer moisture content. This new device emits significantly less radiation, making it safer to use for field technicians, and easier to manage as it does not have the significant requirements for transport, storage, device handling, and personnel monitoring that are typical for traditional NDGs that are governed by Nuclear Regulatory Commission (NRC) requirements. Currently, very few studies have been conducted in order to provide a direct comparison between these two devices, which are essential for assessing the reliability of this new low-activity hybrid nuclear-electric density gauge. To aid in this effort, an experimental study was conducted by testing five native soils within the state of Delaware to examine the relative differences between unit weight and moisture content measurements made utilizing these two devices. Results from this study indicated that on a point-by-point basis, both gauges are able to produce near-identical wet unit weight measurements regardless of soil type. However, a soil-specific calibration is required for the EGauge for reliable moisture content determination purposes, as results from this study showed the difference between the EGauge’s moisture content value relative to the in situ moisture can be as high as 5% when not calibrated.

The grain size characteristics of sandy beach sediments can vary on spatiotemporal scales. To address this, several automatic grain sizing techniques that use digital images to develop the grain size distribution curves have been developed. However, the moisture content is often not accounted for in these methods, despite its known influence on image tone and highly variable nature at sandy beaches. In this paper, a simple method to account for moisture content variation at sand beaches when applying AGS is tested. This involves a series of image preprocessing steps and a correction factor, β, that is used to convert the results of grain size curves obtained from one method so they are equivalent to another method. Previous work suggests that there is a single value of β. However, for the sands tested, it was found that β decreased as the moisture content increased. The results of this study demonstrate that the moisture content influences the grain sizes and grain size distribution characteristics derived from automatic approaches, and can be accounted for using a simple correction factor that is a function of the moisture content.

This study uses molecular dynamics (MD) simulations to evaluate the effect of salt concentration on the thickness of the diffused double layer (DDL) around clay particles. The electrolyte system for the model used in this study is built by implementing the kaolinite system suggested by Bish combined with the SPE/C water system and sodium chloride (NaCl) in LAMMPS (large-scale atomic/molecular massively parallel simulator). Effects on the basal surface of kaolinite clay particles are studied due to its larger surface area compared to the clay edges. CLAYFF intermolecular force fields, including typical 12-6 Lennard-Jones and coulomb interactions, are used for the potential setup with the PPPM long-range solver. Simulations proceeded under different NaCl concentrations ranging from 1% to 10% by weight to capture the range of both low and high salinities. Quantitative analyses, including thermodynamics, radial distribution function (RDF), and coordination number (CN), are applied at different salt concentrations to capture the interactions within the electrolyte system and DDL’s thickness variations. To observe the interactions among clay, water, salt, and the evolution of DDL, visual molecular dynamics (VMD) is used as a visualization tool for this study. The results show that salt presence within the saline water decreases the peak of the RDF and the number of nearest neighbor lists. In addition, DDL thickness around the clay surface tends to decrease because of increasing water salinity with higher reference ion concentrations. The key contribution of this study is a robust evaluation of the change in the DDL thickness under various salinity concentrations and an understanding of the underlying physics and interactions between clay, water, and salt from a molecular viewpoint.

Subsurface exploration is vital for characterizing the soil engineering properties at project sites. Current in situ testing methods often face challenges in providing necessary reaction forces in sites with limited accessibility or with stiff surficial layers (i.e., desiccated or gravelly crusts). This paper presents two investigations on the circumnutation-inspired penetration strategy to decrease the vertical penetration forces. Both investigations were performed on dry sands, one consisting of experimental tests using a robotic arm and the second involving discrete element modeling (DEM) simulations. In plant-inspired circumnutative penetration, the penetrometer’s tip follows a helical path. The bio-inspired probes used in this study have conical tips that are bent at an angle and the entire probes are rotated at different angular velocities while they are advanced into the soil at a vertical velocity. The cumulative total work required to push the probes (i.e., the sum of the rotational and vertical work) was calculated and compared with that involved in quasi-static penetration (i.e., in cone penetration tests). Both the experimental and simulation results show a dependence of the vertical force and torque mobilized during penetration on the relative velocity of the probe tip, defined as the ratio of the tip’s tangential to vertical velocities. Namely, the vertical penetration force decreases as the relative velocity is increased, leading to a decrease in vertical work. The torque remains relatively constant for the circumnutation tests, but the rotational work increases with relative velocity. The total work of circumnutative penetration is similar or slightly smaller than that required for quasi-static penetration for small magnitudes of relative velocities for both experimental investigations and simulations. These findings show that circumnutative penetration can mobilize significantly smaller lower penetration resistances than quasi-static penetration while requiring a similar or slightly smaller amount of work. The reduction in penetration force would allow smaller equipment to be used in site investigation soundings.

Hydraulic conductivity and soil compressibility are known to be interdependent characteristics of soils. For agriculturally productive regions, such as San Joaquin Valley (SJV) in central California, certain agriculture practices, for example, overdraft of groundwater during drought periods, have caused excessive settlements in the region. While the effect of pumping has been extensively studied and monitored, the impact of other agricultural practices, such as fertilizer usage, is understudied. Therefore, an experimental study was undertaken to examine and compare changes in hydraulic conductivity and compressibility characteristics of soil treated with variable fertilizer concentrations. The results indicated the hydraulic conductivity increased, compression index decreased initially and then increased, and the coefficient of consolidation decreased with the increase in fertilizer concentration. An example of field application is included to illustrate the effect of changed characteristics on settlement estimations. Based on these findings, the authors conclude that fertilizer treatments were found to initiate changes in soil’s hydraulic characteristics and may accelerate consolidation settlements.

This paper introduces a new paradigm that integrates the concepts of particle abrasion and breakage. Both processes can co-occur under loading as soil particles are subjected to friction as well as collisions between particles. Therefore, the significance of this integrating paradigm lies in its ability to address both abrasion and breakage in a single framework. The new paradigm is mapped out in a framework called the particle geometry space. The x-axis corresponds to the surface-area-to-volume ratio (A/V), while the y-axis represents volume (V). This space facilitates a holistic characterization of the four-particle geometry features, that is, shape (β) and size (D) as well as surface area (A) and volume (V). Three distinct paths (abrasion, breakage, and equally occurring abrasion and breakage processes), three limit lines (breakage line, sphere line, and average shape-conserving line), and five different zones are defined in the particle geometry space. Consequently, this approach enables us to systematically relate the extent of co-occurring abrasion and breakage to the particle geometry evolution.

This paper presents the results of a site-specific study correlating Becker penetration test blow counts to that of the standard penetration test. The study was conducted as part of the Woodfibre LNG export facility project. The project site is located near Squamish, British Columbia. Site investigation for the project included standard penetration tests, Becker penetration tests, and instrumented Becker penetration tests. The blow count values from the three different test methods needed to be converted to equivalent standard penetration test values for use in seismic analyses and design of the various LNG infrastructure types. Four different methods and correlations were evaluated. Comparison of the equivalent blow-count data obtained from adjacent boreholes with different test methods shows wide differences in the resultant equivalent standard penetration test values obtained using currently available conversions methods. We propose site-specific conversion factor to correlate blow-count data from the different test methods for sand and gravel soil types. This paper also presents a framework to correlate the bounce chamber pressure and hammer energy measurements, which can be used to convert the blow counts from Becker penetration tests to equivalent standard penetration test values.

The NorSand critical state constitutive model is a simple material model, which is popular in the analysis of the static liquefaction problem in tailings. In this paper, NorSand’s historical development and applications to geotechnical engineering practice are discussed, and single element simulations of NorSand are compared to laboratory test results to display to what extent the model is or is not capable of capturing the essential aspects of behavior under common loading modes and their boundary conditions within the framework of NorSand’s constitutive relations. To explore to what extent the material behavior can be captured, the critical state line for Toyoura Sand is adjusted to better capture the behavior of loose undrained tests on soil. NorSand is found to accurately predict drained triaxial material behavior and the behavior of dense soils, but struggle with accurately predicting the behavior of loose soils when zero total strain boundary conditions are applied.

Amsterdam, the capital of the Netherlands, has just started a comprehensive canal quay wall renovation in order to cope with deterioration and sporadic but increasing failure of their extensive canal system. The pressed-in pipe pile quay wall was built as a pilot quay wall renovation project to prove the method’s speedy, economic, and environmental advantages after it was selected out of various alternative construction methods. The project installed 272 508-mm diameter pipe piles by rotating and simultaneously pressing them into the existing quay wall structure. The toe of each new pipe pile was equipped with a cutting shoe to be able to cut through the existing structures and the ground. The piling machine and the other auxiliary equipment, except a conventional support crane, were electrically powered for the goal of less emissions of carbon dioxide. Along the canal was a narrow roadway with a line of tall trees and densely built mid-rise residential/commercial buildings which required careful construction planning and execution.

Geotechnical designs of mine waste rock (WR) piles require the critical friction angle (ϕ_cr) of the coarse crushed rock. For this purpose, grading scalping techniques must be used to accommodate the minimum recommended sample aspect ratio α = D/d_max into experimental shear devices (where D is the size of the sample and d_max is the maximum particle size). Nevertheless, international standards do not agree on the minimum α for a representative sample, and its effects are poorly understood. This paper aims to investigate the effects of grading scalping and α on ϕ_cr of WR samples. Drained triaxial tests were conducted on medium and large cylindrical samples of D = 150 and 300 mm, respectively, using α varying from 4 to 30. The results show stable ϕ_cr for α ≥ 12, advocating that the recommendation of α = 6 given by the standard ASTM D7181 might be too low and should be revisited after comprehensive testing.

Tailings dams are constructed as a means of containing the byproducts of mining operations. They are often built using the coarser fraction of the tailings referred to as the tailings underflow or tailings sand. Due to the expected high overburden pressure, grain crushing may occur at the base of tall tailings dams. This may result in reduced hydraulic conductivity or drainage capability, thus undermining the long-term performance of the dam. To accurately evaluate the safety margin when designing tall tailings dams, it is important to understand the evolution of the hydromechanical behavior of the tailings sand. In this paper, laboratory-scale high-stress compression tests were conducted, and hydraulic conductivity measurements were taken using a specially designed oedometer cell. The experimental results were then analyzed using an enhanced continuum breakage mechanics model. The results indicate that an increase in stress from 5 to 40 MPa can result in an increase in fines content (mass percentage of particles smaller than 0.075 mm) from 11% to 17% and a corresponding decrease in hydraulic conductivity of up to one order of magnitude for the tested materials. We also report the preliminary results of a three-month creep test on tailings sand subjected to 3 MPa confining pressure to study the time effect associated with grain crushing.

An approach is presented for quantifying surface heterogeneity of granular layers based on digital analysis of images taken using low-cost, widely available equipment. The method enables rapid survey of large surface areas with high spatial discretization. Inputs to the analysis routine are RGB pictures of the aggregate surface, while key outputs are approximate size distributions and a descriptor termed “median feature size” (MFS). The routine is comprised of four main stages: contrast enhancement, noise reduction, segmentation, and data analysis/visualization. The paper discusses the application of the method for characterizing aggregate layers built at four sites. MFS data effectively capture spatial variability of the aggregate surface coarseness, providing a means to quantify material heterogeneity produced by segregation processes. Statistical analyses demonstrate a correlation between MFS and in situ hydraulic conductivity, and support the notion that the MFS is an indicator of local heterogeneities driving variability of hydraulic conductivity at the local scale.

This paper presents the results of a numerical investigation into the combined influence of static shear bias and post-peak strength loss on the cyclic behavior of plastic silts and clays at the element and system level. Numerical analyses were performed using the finite difference program FLAC 8.1 with the PM4Silt constitutive model. The element-level impact was investigated using stress-ratio controlled, undrained, cyclic direct simple shear loading simulations with different magnitudes of initial static shear stress and uniform cyclic stress cycles. System-level impacts were investigated with nonlinear dynamic analyses of a levee using a ground motion recording from the 1999 Kocaeli earthquake. Six PM4Silt calibrations were considered to represent a range of clay soil properties. Study findings show that strength loss did not significantly influence the cyclic behavior at the element level; however, strength loss had substantial impact on the overall performance of the levee system, particularly regarding crest deformations and accelerations. The implications of the results on practice and future research needs are discussed.

Direct simple shear (DSS) tests are widely used to capture the shearing behavior of soils. A major concern with a DSS test is the non-uniform distributions of stress and strain on the horizontal platens of this device. A series of DSS simulations were carried out in this study using 3D discrete element analysis (DEM) to examine the effects of specimen size and boundary conditions. The gradation of a coarse sand was used to generate different sphere sizes, which were then uniformly spread throughout the model. While smooth lateral walls were used, the horizontal boundaries had a high coefficient of friction to minimize slippage. A constant-volume condition was imposed by controlling boundary displacements. Different specimen diameters were modeled to examine the effect of diameter-to-height ratio (D/H) on stress path, peak shear stress, and post peak behavior. Numerical simulations indicated that boundary effects became more prominent at higher consolidation stresses for a given D/H. Such boundary effects were, however, reduced by enlarging the sample diameter (i.e., raising D/H). Specimen boundary effects were minimized in specimens with a D/H ≥ 2.8, resulting in the same shearing behavior as those with larger D/H ratios.

Although the simplified method can be used to approximate the cyclic resistance of plastic soils, recent experience in the Pacific Northwest indicates that the SHANSEP-based framework implemented in this method can overestimate cyclic resistance for low plasticity silts. This paper presents a statistical model developed for the estimation of the cyclic strength ratio, τ_cyc/s_u,DSS, of silts for the number of uniform loading cycles, N, corresponding to cyclic shear strain failure criteria ranging from 1% to 10%. The database used for model development and statistical modeling procedure are described. The relative importance of overconsolidation ratio, OCR; plasticity index, PI; fines content, FC; and void ratio, e, on τ_cyc/s_u,DSS is evaluated, followed by nonlinear regression analysis to finalize fitted model parameters. OCR was excluded from the proposed model due to the strong correlation between OCR and undrained shear strength of silt. Strong correlation between e and PI lead to apparent multicollinearity and the need to consider just one of these two variables in the final statistical model. The τ_cyc/s_u,DSS estimates using the proposed model and those obtained from a previously developed cyclic resistance ratio-based model improve as the cyclic shear strain failure criterion increases. The statistical model returns τ_cyc/s_u,DSS increasing from 0.47 to 0.68 as the cyclic shear strain failure criterion increases from 1% to 10% for N = 30 and PI = 10, whereas for PI = 30, τ_cyc/s_u,DSS increases from 0.51 to 0.75. The proposed model may be used in a future performance-based earthquake engineering framework to link estimates of the strain-dependent τ_cyc/s_u,DSS to the consequences of cyclic failure.

This study aims to assess feasibility of microbial biopolymer application to enhance thermal dissipation efficiency of backfill soils surrounding underground electricity cable tunnels. In detail, microbial biopolymer, graphite, and fly ash were suggested as additional additives, and different combinations of additives were assessed through a laboratory thermal conductivity measurement system. The effects of additive content on soil-additive admixture and water content were evaluated. The soil-biopolymer mixture has 15.2% higher thermal conductivity at 20% water content than untreated soil, but is 11.3% lower at 10% water content, so the biopolymer itself does not significantly contribute to the improvement of soil thermal conductivity. However, in the case of the soil-biopolymer-graphite mixture, the thermal conductivity increased by up to 46.4% compared to the untreated soil at a water content of 20%, which was 16.9% higher than that of the soil-graphite mixture. This is due to the pore-clogging behavior of the microbial biopolymer.

Calcined clay (CC) is often used to stabilize problematic soils through its cementitious property. The mechanical behavior of CC might differ from that of raw clay due to calcination and the presence of calcite impurity. The safety and design of the infrastructure built on hilly and sloped clay terrains are influenced by the residual shear strength. Many studies have been done to understand the influence of stress history, strain rate, clay mineralogy, and normal stress on the residual shear strength of clay soils. However, available studies on the residual shear strength of CC are scarce, although it is essential for slope stability analysis. This study investigated the drained torsional shear and volume change response of compacted and slurry calcinated kaolin samples from the laboratory ring shear test under three different normal stresses. The anomalous peak shear response was observed under the volumetric contractive behaviour for calcined kaolin clay in normally consolidated (NC) conditions. Further, the clay particle associations were investigated at different stages of shearing in NC conditions using the field emission scanning electron microscopy (FESEM) technique. FESEM analysis indicated that the anomalous peak behavior was attributed to the cementation bond between the clay particles.

Natural rubber is a frequently utilized material for vibration isolation due to its remarkable energy absorption properties. A few recent studies reported the use of natural rubber, in the form of rubber tyre crumbs, for preparing geotechnical seismic isolation (GSI) layers. In this technique, the soil beneath the foundation is replaced with a layer of sand and rubber chips. However, it can only be used for newly planned constructions. The present study explores the feasibility of transforming a naturally occurring sand layer into a GSI layer by permeating it with natural rubber latex (NRL). The advantage of this treatment is that it is possible even beneath already-existing structures. For this purpose, a preliminary assessment of dynamic properties such as cyclic shear modulus and damping ratio of loose uniform fine sand permeated with NRL was conducted over a range of shear strains by performing cyclic triaxial tests and resonant column tests.

The magnitude of swelling pressures must be accurately estimated/predicted using appropriate methods for a safe design and performance of pertinent geotechnical infrastructure on expansive soils. This paper reviews various methods used by researchers in the past decades to quantify swelling pressure in different directions. Methods reported in literature for the determination of swelling pressure can be categorized into experimental, analytical, and numerical studies. Laboratory methods are affected by scaling and boundary effects, whereas fields tests are time consuming and expensive; however, numerical models with appropriate validation can predict swelling pressures efficiently. Various factors that affect swelling pressures are clay mineralogy, dry density, initial water content, boundary conditions, and matric suction. In the present critical review, it is observed that matric suction, a significant factor affecting the swelling behavior of unsaturated expansive soil, was considered in only a few studies.

Expansive soils pose significant challenges in geotechnical engineering due to their high swelling and shrinkage potential, damaging structures and infrastructure. While various methods have been employed to address these issues, nano-conditioning using nanoparticles presents a promising avenue. Nanoparticles, due to their small size and large specific surface area, can interact profoundly with soil, impacting its physical, mechanical, and hydraulic properties. Due to the limited information available on the effects of nano-conditioning on expansive soils, our research adopts an extensive literature review approach. This approach involves gathering data and studies related to the use of nano-conditioning for general soil treatment, with a focus on factors pertinent to expansive soils’ behavior. The results reveal the complex and context-dependent nature of nanoparticle-soil interactions. Nano-conditioning can enhance certain properties, like compressive strength and elastic modulus, while its impact on parameters such as plasticity index, cohesion, and friction angle varies depending on nanoparticle type and concentration.

Soil liquefaction is a phenomenon where soil loses its strength and stiffness during strong shaking or vibrations, which can lead to a change in the volume of the soil following liquefaction. This process can have significant consequences on infrastructure in earthquake-prone areas. To better understand the impact of soil liquefaction, many studies have focused on evaluating the post-liquefaction volumetric strain. However, there have been few studies that have isolated the effects of particle angularity on post-liquefaction volume changes. The objective of this study was to better understand the effect of particle angularity on post-liquefaction volumetric strain. To achieve this, the study compared two types of sands, one rounded (35-50 silica) and one sub-angular (#2 quartz). A cyclic simple shear device was used to perform the liquefaction and post-liquefaction tests, and the specimens were prepared in a loose state while achieving the same density and void ratio, ensuring consistency between the two different sands. The specimens were consolidated to a pressure of 100 kPa and were then subjected to cyclic shear at a constant volume. Cyclic stress ratios ranging from 0.05 to 0.3 were used to perform cyclic liquefaction tests. The results of the laboratory tests showed that sub-angular sand had approximately half of the volumetric strain after liquefaction compared to the rounded sand. Results were compared with existing relationships for post-liquefaction volumetric strain prediction, and it was found that the relationships overpredicted strains for the sub-angular sand. The findings of this study are important in providing a deeper understanding of the effects of particle angularity on soil liquefaction and post-liquefaction volumetric strain.

Damage to embankments containing slurry-deposited coal combustion product (CCP) can lead to static liquefaction or slope failure, resulting in the release of the contained material. Characterization of the mechanical and hydraulic properties of CCP deposits provides the fundamental basis for the design, operation, and closure of CCP facilities. In this study, centrifuge experiments were performed to evaluate the changes in the cone penetration test (CPT) tip resistance (q_c) due to differences in drainage conditions and the location of the water table within an initially dense fly ash deposit. To accomplish this, centrifuge equipment that enables dewatering and rewetting of CCP deposits in flight was built and commissioned. Test results show the dependency of the CPT q_c on the penetration rate, consisting of an increase in q_c as the penetration conditions transition from drained to undrained due to the dense state of the deposit that led to the generation of negative excess pore pressures during penetration. The changes in pore water pressure/suction, gravimetric water content, CPT q_c, and shear wave velocity during dewatering and rewetting were monitored to deduce changes in fly ash strength and stiffness. The finding can help develop or refine correlations between the CPT tip resistance and the in situ state of CCP deposits as well as relate properties measured in the laboratory to the in situ hydraulic response of CCPs.

Eastern Canadian clays are characterized by high sensitivity and compressibility and warrant the need for an appropriate estimation of the undrained shear strength for a safe geotechnical design. A multivariate geotechnical database consisting of natural water content, Atterberg limits, undrained shear strength, effective vertical stress, preconsolidation pressure, and overconsolidation ratio from 49 sites in Eastern Canada is compiled from literature for this purpose. The primary objective of this study is to analyse the dependence of undrained shear strength on the aforementioned parameters and propose a correlation that satisfies practical conditions through regression analysis. Bias and uncertainties of existing empirical correlations are assessed. A comparative study is also made with sensitive clays of Norway and Sweden. The results show the poor correlation of Eastern Canadian clays with index parameters and their strong dependence on the stress history of the soil.

Microbially induced carbonate precipitation (MICP) is a biogeochemical process that uses microbes to create favorable conditions in a porous medium for bio-cementation. The hydrolysis of urea and the resulting variation in pore-scale chemistry creates variations in MICP. Research is needed to characterize the spatial and temporal development of precipitation at the particle level that influences soil properties and mechanical behavior due to varying granular characteristics. Several researchers have used reactive transport modeling to predict precipitation distribution patterns over meter-length scales; however, this continuum approach is less applicable for assessing varying granular characteristics at the pore-scale. This study investigates agent-based modeling (ABM) as a new framework to simulate complex interactions at the micro-level to generate phenomena observed at the macro-scale. In this study, an ABM was developed to simulate urea hydrolysis by simplifying the complex biogeochemical interactions between the bacteria Sporosarcina pasteurii and an aqueous MICP environment, including the pH-dependent ammonium speciation. Results show that the ABM captures similar urea degradation trends compared to existing reactive transport models and experimental data. Additionally, insights from the ABM suggest that nutrient depletion zones emerge during ureolysis and are influenced by super-agent size and distribution. These findings indicate that ABM can provide additional insights into the MICP process that cannot be captured by reactive transport modeling.

This paper reviews recommendations regarding criteria and engineering procedures for evaluating undrained cyclic strengths of sand-like, clay-like, and intermediate soils. The need to distinguish between cyclic strength evaluation criteria and liquefaction susceptibility criteria is illustrated by reviewing two common procedures—one where these two criteria are coincident and one where they are not. Furthermore, a review of alternative liquefaction susceptibility criteria illustrates that their differences can reflect differences in terminology/definitions or intended purpose/application. A logic tree approach is used to illustrate that cyclic strength evaluation criteria, whether explicitly stated or implied, are an essential step in engineering evaluations of potential ground failure or deformations, whereas liquefaction susceptibility criteria that do not coincide with recommended cyclic strength evaluation procedures are not. Cyclic strength evaluation criteria and engineering procedures for evaluating undrained cyclic strengths of sand-like, clay-like, and intermediate soils are described and illustrated through example applications.

The US Army Corps of Engineers seeks to beneficially use 70% of sediment dredged by 2030, which equates to approximately 30 million cubic yards annually. One option to achieve this is the beneficial use of dredged material (BUDM) to supplement marsh elevation, bolstering the long-term stability of the natural infrastructure. In the BUDM design process, target elevation throughout the design life must be determined, which requires a holistic understanding of external factors such as tidal ranges, local hydrology, subsidence, accretion, and projected sea-level rise rates. However, determining a target elevation is only half the problem as one must also determine the magnitude and rate of consolidation. Hydraulically dredged sediment is deposited in a fluid state and will undergo large deformations. Engineering uncertainty is highly prevalent in coastal projects due to the difficulty in quantifying the engineering properties of soft deltaic soils. In 2020, the USACE Philadelphia District (NAP) began a multi-phase BUDM project to use sediment from a waterway maintenance event to supplement a back-bay island. The observational method was utilized to calibrate consolidation models against data collected during the first two placements to better predict elevations following a future placement. The comparison against elevation data showed that base models underpredicted the magnitude of consolidation which would have compounded to a 17% difference between the base and calibrated models following the third placement.

This paper presents the effects of penetration rate on peat penetration resistance measured with miniature full-flow penetrometers (T-bar and ball). The accuracy of the 20 mm/s standard penetration rate of penetration testing in peat is doubtful. The investigation is conducted by performing a series of miniature full-flow penetration tests in a pressure chamber using various penetration rates under different vertical effective stresses. The results show that the T-bar and ball penetrometers exhibit comparable penetration resistance values at the same penetration rates and effective stresses. The rate effect is interpreted in terms of a non-dimensional penetration rate with the aid of coefficient of consolidation values obtained from one-dimensional oedometer tests. The non-dimensional rate shows that the penetration resistance decreases with an increase in the penetration rate. A transition point from partially drained to undrained responses was determined from the interpretation. Finally, penetration rates for standard field testing were recommended.

Dynamic properties of soil, such as shear modulus and damping ratio, are necessary for analyzing the dynamic response of the soil in geostructures. This study investigates the effects of partially inherent anisotropy and stress-induced anisotropy on the shear stiffness of unsaturated soil through a series of dynamic hollow cylinder tests at medium strain levels. The different inherent anisotropy in tested sand specimens was introduced through different compaction water contents in the sample preparation stage while keeping the void ratio nearly constant. Moreover, the influences of the angle of maximum principal stress, α, and intermediate principal stress parameter, b = (σ₂ − σ₃)/(σ₁ − σ₃), as stress-induced anisotropy parameters are examined at the dynamic loading stage. The experimental results suggested that the b-parameter has no noticeable influence on shear modulus. On the contrary, shear modulus values showed a peak by changing the value of α from 15° to 75°, with symmetric trends with respect to α = 45°. The impact of compaction water content on the stiffness-α trend was negligible, whereas it affected the stiffness-b to some extent.

Pyroclastic sands derived from intermediary weathering of volcanic rocks and other volcanic deposits have a mineralogy dominated by minerals other than silica. This affects both particle crushability and roughness, which leads to differing intrinsic soil properties. Natural deposits of pyroclastic sands can be found in areas of active and paleo vulcanism, and a famous example is the Shirasu sand of the Japanese island of Kyushu. Specimens of pyroclastic pumice and scoria were milled to a consistent gradation and tested in undrained cyclic simple shear to study their undrained cyclic shear behavior. Mineralogy and elemental composition of the two pyroclastic sands is confirmed post-milling using X-ray fluorescence analysis (XRF). Experiments were conducted at a normal stress of 100 kPa, while applied cyclic shear stress ratios varied from 0.2 to 0.5. Using 3.75% double strain amplitude criteria for liquefaction, the number of cycles to liquefaction was observed for these two materials. Post-cyclic residual strength measurements were also performed. This experimental study furthers the growing evidence in the geotechnical literature that intrinsic soil properties such as critical state friction angle and Bolton’s Q and R parameters are fundamental drivers of undrained cyclic shear behaviors of liquefaction and cyclic softening.

Soil thermal conductivity k plays a crucial role in analysis and design of different systems that rely on thermal interaction with the ground. Research indicates a significant difference between k values estimated using transient-state and steady-state methods. Apart from the rate of soil temperature increment, soil composition also influences the difference between transient-state thermal conductivity k_tr and steady-state thermal conductivity k_st. Such a deviation of k_st from k_tr of sand-kaolin mixture is overlooked in the literature. This research focuses on the influence of fines percentage on thermal conductivity of sand-kaolin mixtures. A specially designed consolidometer, which is capable of measuring both k_st and k_tr from soil temperature profile derived from a single test, was used in this research. Results demonstrate that the percentage of fines filling the pore space significantly influences heat conduction, and thereby effective thermal conductivity of the mixture.

This study explores the elastoplastic response of Opalinus clay, a host rock for waste repositories, under thermo-mechanical loading. A fully coupled thermo-hydro-mechanical (THM) model is developed using a finite element model in COMSOL Multiphysics Software. The developed model is used to predict the THM response of a fully saturated sample of Opalinus clay in a hollow cylinder triaxial cell under different heating-cooling cycles in both drained and undrained conditions. The results demonstrate the importance of accounting for elastoplastic behavior and considering the effect of temperature on the THM properties of clay in predicting the stress-strain responses of claystone under THM loading. The role of drainage conditions is analyzed, and the results of pore pressure and volumetric strain are compared with experimental measurements, showing good agreement. A dilative behavior is seen in the heating phase until it reaches its highest experienced temperature and then a contraction behavior is observed, and the compression behavior is continued with the cooling phase in a naturally consolidated sample.

Seepage cut-off walls are common seepage mitigation measures in dikes to minimize seawater ingress. These cut-off walls are usually made of cement-bentonite (CB). The quality of this CB wall is critically important. Non-destructive testing would ensure quality control/assessment without damaging the wall’s integrity. One such non-destructive technique is the measurement of electrical resistivity. Correlations can be established between electrical resistivity, strength, and permeability of CB mixes. Continuous monitoring of electrical resistivity across the CB wall would enable early detection of its properties instead of waiting for coring of samples after 14, 28, or 91 days of curing, which would introduce discontinuities in the wall. For in situ electrical resistivity measurement, electrodes of finite size are buried in an infinite soil medium, where A_s, the area of soil mass is much larger than A_e, the area of electrode. This is very different from laboratory measurement, of which A_s = A_e. Thus, the effect of boundary on these two situations is very different, and the correlation between resistivity and unconfined compressive strength, as well as between resistivity and permeability, established in a laboratory setup may not be suitable for use in in situ measurement condition. Hence, this paper aims to systematically study the impact of boundary on the electrical resistivity of CB mix. Consistent CB mix placed in boxes of different heights and widths (thus different values of A_s) was designed to study the boundary effect, with area of electrodes (A_e) kept constant. It was found that the electrical resistivity value increases with reducing A_s/A_e value, and A_s/A_e has to be greater than 25 to negate the effects of boundary on electrical resistivity. In addition, there is an issue on the direction of resistivity measurement. The in situ resistivity measurements were more conveniently carried out horizontally in an infinite soil medium, while the laboratory cored samples were normally measured in vertical direction. Thus, there is a need to study the anisotropy effect on electrical resistivity value of CB mix.

High-resolution mapping of near surface soil moisture is important for the characterization of landslides. This study focuses on estimating the near surface soil moisture through UAV-enabled high-resolution topographic, visible, multispectral, and thermal remote sensing data collected over four acquisitions in a six-month period. The spatial distribution of surface soil moisture is estimated via remotely sensed parameters on an active, slowly moving landslide in the San Francisco Bay Area. Regression analysis shows statistically significant correlation between the diurnal temperature difference and measured in situ volumetric water content. Additional predictive features are also engineered from collected spectral and topographic data and used in multivariate regressions. The findings of this study show promise in the prediction of near surface moisture via remote sensing on a variety of surface types and diurnal heating conditions.

The physical and mechanical characterization of the subsurface under hillslopes is critical for understanding the distribution of mass wasting by landslides and debris flows, which are two significant processes that drive topographic change in steep environments. Hillslope environments are notoriously spatially complex. However, subsurface characterization is rarely performed on regional scales due to challenges in characterizing highly localized variations. Common methods for subsurface characterization involve costly site-specific sampling and testing leading to point measurements or regional remote sensing techniques. Currently, a gap in scale compatibility exists between site-specific analysis where characterization of the subsurface is robust but spatially limited and regional hazard analyses where characterization is limited to regionally broad categories based on lithology, slope, and/or vegetation. This research explores electromagnetic induction (EM) as a scalable approach to characterize relative differences in physico-mechanical properties of the subsurface in steep terrain where mass wasting is common. For this study, EM data was collected in different geologic units across southwest Puerto Rico (PR), then converted to apparent resistivity values. The apparent resistivity of lithologic groups and limestone subunits were statistically compared leveraging the large datasets collected. Two study areas are selected to examine spatial trends and the effects of topographic factors. The results indicate that EM can detect differences between and within geologic units/subunits and help estimate subsurface heterogeneity where detailed mapping is unavailable.

Due to its geographic location and geologic conditions, the southeast Texas (SETX) coast has been exposed to geological hazards, including land subsidence, floods, and coastal erosion. This study aims to assess recent subsidence areas and rates to understand their impact on flooding in SETX. The persistence scatterer interferometric synthetic aperture radar (PS-InSAR) method was applied in the study area using Sentinel-1 SAR satellite data with descending orbit observations from January 2020 to March 2023. The results show that subsidence areas were observed over northwestern Houston of up to 2 cm/year, consistent with GPS and groundwater-level data. The study highlights the significant temporal and spatial variations in subsidence rates, largely influenced by local groundwater extraction practices. By promoting the integration of InSAR, GPS, and groundwater measurements, this study seeks to contribute to mitigating subsidence and flood hazards in the SETX area.

Full waveform tomography offers an effective method by which to evaluate near-surface conditions and reconstruct a subsurface model in the presence of strong heterogeneities. Because full waveform inversion (FWI) of seismic waves directly inverts both the phase and amplitude information of all recorded waveforms in a dataset, the resolution capabilities are improved relative to other seismic methods that rely on first-arrival times or dispersion-based analyses. FWI proceeds by generating a forward model that numerically simulates wave propagation within the domain. A single-objective inverse problem is subsequently formulated and solved using deterministic optimization algorithms to minimize the misfit between the observed field and simulated model waveforms. However, FWI is highly sensitive to the initial model. Poor misfit between the initial model and the true subsurface conditions can lead to inaccurate results from the inversion converging to local minima or failing to converge at all. One approach to mitigate this ill-posedness is to carefully select an appropriate objective function to characterize the misfit between field and synthetic waveforms. The misfit function often represents a tradeoff between inversion ill-posedness and resolution of the reconstructed subsurface model. The most common FWI objective function characterizes the misfit using a least-squares approach (i.e., L2 norm). However, the L2 norm misfit function tends to trap in local minima and may fail to converge for models with strong heterogeneous subsurface features, particularly when a poor initial model is selected. In this study, the recently proposed optimal transport misfit function was explored when applied to a near-surface domain. This misfit function relies on optimal transport theory, which develops a more effective measure of distance between probability distributions and exhibits reduced non-convexity relative to the least-squares misfit function. Both misfit functions were applied to invert waveform data acquired from a model with a subsurface sinkhole feature. Performance of the two misfit functions was evaluated by comparing their subsequent inversion results obtained from different starting models. The optimal transport misfit function was found to be more robust than the least-squares misfit and exhibited fewer convergence issues when a poor initial model was used for the FWI.

Frozen soil displacement variations induced by seasonal factors present significant challenges to infrastructure stability in cold regions. This study employs interferometric synthetic aperture radar (InSAR) technique to track the seasonal ground heave and settlement of an airport runway situated in Qinghai Province, China. The analysis utilizes the StaMPS-InSAR method, incorporating 65 C-band SAR images obtained from the Sentinel-1 satellite. Through analysis, the persistent scatter (PS) locations are initially identified. Subsequently, the annual displacement rates of PS are mapped and integrated with a land use map. Lastly, time series displacement variations are assessed for PS on both the airport runway and shoulder to evaluate the annual maximum heave and settlement there. Based on the PS InSAR analysis, the mean seasonal heave and settlement for the runway area are 1.5 and 2 mm, respectively. In contrast, the shoulder area exhibits 2.8-mm mean seasonal heave and 2.5-mm mean seasonal settlement. These findings highlight a reduced magnitude of frost heave on the airport runway when compared to the shoulder, a trend consistent with general observations from the site. The work demonstrates the applicability of InSAR as a method for monitoring seasonal ground heave and settlement in cold regions.

There are many dams around the world where the cost of maintenance or renewal exceeds the expected future benefits. These dams may be considered for removal due to various reasons such as economics, dam safety, recreation, change in water stream direction, or ecosystem restoration to provide fish passage. Sediment management is one of the main challenges for dam removal projects, which can effectively control the budget and safety of the project for the next use of the river and dam site. The released sediments after dam removal can impact the stability or erosion of the riverbanks and increase water turbidity. Based on these concerns, it is critical to estimate the sediment volume and evaluate any associated issues before starting dam removal activities. In this study, a series of electrical resistivity tomography (ERT) survey lines were conducted perpendicular to the axis of the river to evaluate the depth of the fine grain and gravel soil deposited along with the bedrock depth for the project site to support river restoration planning. Each ERT survey line was composed of 56 electrodes starting from the east bank of the river and ending on the west bank including 14–20 underwater electrodes, depending on the width of the river at each cross-section location. Boring logs and field observations were implemented to validate the results of the ERT survey. Data are presented in 2D cross sections showing the electrical resistance of different soil layers. Based on the interpretation of the results, low resistivity near-surface layers are in close proximity to the riverbanks which mostly contain fine grain soils and could be sensitive to erosion and instability concerns following the removal of the dam. The depth of the soil layers resolved in the ERT cross sections agreed well with the boring logs, confirming the ERT method can be a useful tool for estimating the sediment depth in dam basins. This initial result can be used with supplemental field measurements for better sediment management for the project.

The potential of synthetic aperture radar (SAR) data to derive coastal soil types is discussed. SAR systems, which are all-weather satellites, can provide data during storm events and allow for the derivation of soil type in all conditions, regardless of cloud coverage. SAR images are composed of the energy that is returned after hitting the ground, known as the backscatter. This backscatter is impacted by both radar properties (wavelength of the transmitted signal, incidence angle, and polarization) and terrain characteristics (dielectric properties, surface roughness, and feature orientation). In this study, data from the publicly available C-band Sentinel-1A satellite was used to assess three distinct tidal flats (two fine-grained, one coarse) on the Great Bay Estuary in New Hampshire. Across two polarizations (VV and VH), lower backscatter returns were observed for the finer sites (−20.66 and −18.14 dB for VV polarization and −27.85 and −25.82 dB for VH polarization) and higher responses (−10.79 and −23.99 dB for VV and VH, respectively) were observed for the coarser sites. This demonstrates that there are distinct trends in backscatter response for different soil types, suggesting that tools such as machine learning may be able to derive the soil type.

A first-time application of 3D ambient noise tomography (3D ANT) method is presented for detection of deep voids. The method is based on the solution of 3D P-SV elastic wave equations and adjoint-state optimization to directly invert experimental cross-correlation functions (CCF) for extraction of S-wave velocity (Vs) structure. The main advantage of this approach is that it does not rely on assumptions of energy balance and far-field waves as required by methods using characteristics of Green’s function (GF). Instead, the source power-spectrum density is inverted to account for source distribution (location and energy), which allows to exploit full information content of all available CCFs from ambient noise recordings. The 3D ANT capability in detecting deep voids is investigated at a test site in southern Florida. For the field experiment, 72 vertical geophones of 4.5-Hz resonance were deployed in a 4 × 18 grid over 9.0 × 76.5 m area on the ground surface to record noise data for 34 min. The CCFs extracted from the noise recordings have good energy at 5–20 Hz and a consistent wave propagation pattern for the entire test area. The inverted result reveals that the 3D ANT was able to image a large deep void at 28- to 44-m depth, which is generally consistent with results from invasive SPTs.

Gravel and sand shoals may play a significant role for infrastructure impacts during flood events. This study uses high-resolution (30-cm panchromatic resolution at nadir) pan sharpened multispectral satellite images to map sand and gravel shoals near the Cinnabar Basin Bridge in Gardiner, Montana. While the bridge was not damaged during the flood event, erosion of the riverbanks and scour were observed with significant differences noticeable between both riverbanks, which may be related to the presence or evolution of shoals during the flooding. Toward analyzing the role of the shoals on local erosion and scour patterns, the goal of this study is to classify sediments based on soil type (sand, gravel, and cobbles) and color, using unsupervised K-means clustering and spectral information divergence (SID) with images taken in October 2022 and January 2023. The soil classifications from the K-means clustering and SID analysis are then compared to the pan sharped RGB images, drone images, and on-site observations and photos to assess the results from the classifications. The resulting classifications are compared for changes in the composition of the shoals over time from the October image to the January image, but also take advantage of receding water levels over the winter. Both the K-means clustering and SID analysis yield sediment classifications matching the site photos and drone images. Results show that unsupervised K-means clustering and SID can be used to classify sediments into different groups based on soil type and color, which may enable a deeper investigation of the impacts of sand and gravel shoals on infrastructure.

Flooding annually causes thousands of fatalities and billions of dollars in damage globally, while predicting future floods has become increasingly challenging due to changing urban environments and land surface conditions. Furthermore, due to climate change and associated shifts in rain patterns, severe floods are likely to increase. High-water marks collected post-flooding provide key information for advancing our understanding of flood impacts and developing mitigation strategies. However, collecting high-water marks after a flooding event can be complicated due to access issues related to destroyed infrastructure, and detecting high-water marks becomes increasingly difficult with time passing after a flood event. This leads to significant loss of data or risk to personnel entering these recently flooded areas. Here, we present initial data demonstrating the use of multispectral imagery in rapidly collecting and mapping high-water marks post-flooding for different commonly used building materials. This work builds on the exploratory deployment of multispectral imagery during the Geotechnical Extreme Event Association (GEER) response to the July 14, 2021, Western European flood. Additional images were collected in a controlled lab setting to test these initial observations and the potential to extract high-water marks using multispectral imagery of materials commonly used in building façades. These materials included clay bricks, plywood, maple and pine planks, concrete, and steel. Materials were soaked for 48 h after which images were collected at predetermined specific time intervals to establish if and how the signal associated with the high-water mark evolved. For all materials, with the exception of steel, the high-water mark was clearly expressed in the multispectral imagery. Specifically, the blue band (wavelength 465−485 nm) and red-edge band (wavelength 712−722 nm) show the clearest manifestation. Current research is focusing on how the high-water mark can be significantly enhanced and clearly identified through linear combinations of spectral bands. This will enable the development of material-specific indices for rapidly mapping spatially varying flood depths and extents in urban areas during post-disaster reconnaissance. Furthermore, follow-on testing will use sediment-laden water such that the influence of soil adhering to structure surfaces can be incorporated into identifying high-water marks on various structure and foundation surfaces.