Journal of Geotechnical and Geoenvironmental Engineering

Following the Cephalonia, Greece, 2014 earthquake sequence ($M_w=6.1$ and $M_w=6.0$), liquefaction of gravelly earthfill materials at the ports of Lixouri and Argostoli resulted in the manifestation of ground cracking and coarse-grained soil ejecta, and the quay walls in these ports exhibited lateral ground displacements ranging from 0.1 to 1.5 m. To evaluate the seismic performance of the port quay walls, numerical analyses using the finite-difference method were performed, and the results compared with the observed response. Three commonly used constitutive models (PM4Sand, UBCSand, and URS/ROTH) calibrated based on in situ site investigation data were considered in modeling the liquefiable earthfills. The results of the numerical analyses at both ports using the best-estimate parameters indicate that taller walls exhibit smaller lateral ground displacements than shorter walls, something that is in line with field observations. For the shorter walls, liquefaction-induced lateral spreading played an important role in the observed response, whereas for the taller walls, the seismic behavior is dominated predominantly by the dynamic response of the structural system. PM4Sand and UBCSand models seem to yield very similar deformational results, but the URS/ROTH model, which assigns residual shear strength parameters once liquefaction is triggered, resulted in horizontal displacements that are closer to the observations for short-wall geometries but overpredict the response when the effect of liquefaction on the overall displacements is small. Finally, the numerical analyses demonstrate the strong influence of the pulselike characteristics, as well as the polarization of the input motion on the seismic response of the Lixouri quay walls, indicating that forward directivity contributed significantly to the observed quay wall deformations.

Total soil water potential ${\psi }_{\mathrm{t}}$ is conventionally defined as the sum of matric potential ${\psi }_{\mathrm{m}}$ and osmotic potential ${\psi }_{\mathrm{o}}$, i.e., ${\psi }_{\mathrm{t}}={\psi }_{\mathrm{m}}+{\psi }_{\mathrm{o}}$, when gravitational potential is ignored. Soil water isotherm (SWI) is the constitutive relationship between ${\psi }_{\mathrm{t}}$ and soil water content $w$, i.e., ${\psi }_{\mathrm{t}}(w)={\psi }_{\mathrm{m}}(w)+{\psi }_{\mathrm{o}}$, where ${\psi }_{\mathrm{m}}(w)$ is called soil water retention curve (SWRC) or soil water characteristic curve. SWI and SWRC are arguably the two most important soil constitutive relationships because they govern virtually all phenomena in soil such as flow, stress and deformation, and biological activities. A closed-form SWI, recast from a generalized SWRC equation for adsorption and capillarity, is experimentally validated for its generality in representing SWI. Adsorption isotherms of 49 soils, covering all spectrum of soil types with plasticity index up to 185% and specific surface area up to ${600\mathrm{m}}^2/\mathrm{g}$, are used to validate the SWI equation. It is shown that the SWI equation can nearly perfectly represent the isotherms of these soils with almost all of the coefficients of determination $R^2\ge 0.99$, validating the generality of the SWI equation. Comparative analysis is also conducted by using two existing SWI equations, namely, the Brunauer–Emmett–Teller (BET) equation and the augmented BET (A-BET) equation. It is demonstrated that the SWI equation is superior to the BET and A-BET equations in representing soil–water interactions by adsorption and capillarity, and in the full relative humidity range.

Near-fault forward directivity (NFFD) ground motions cause significant potential damage to civil infrastructure. Buildings at soil sites at which NFFD motions are expected might need probabilistic seismic hazard analysis (PSHA) for soil sites considering the NFFD effect. In the analysis, ground motion amplification factors (GMAFs) considering the NFFD effect are required. Thus, investigating the characteristics of GMAFs due to the NFFD effect is important. To achieve this objective, this paper performs probabilistic ground response analyses for two typical soil sites subjected to three ground motion suites, that is, NFFD motions, far-fault motions, and near-fault motions without pulses. The results indicate that pulse periods of NFFD motions significantly affect the characteristics of GMAFs, rendering mean GMAFs remarkably lower or higher than those of ordinary ground motions. This study also reveals that standard deviations of GMAFs are insensitive to types of input motions. By further investigating the influences of soil deposit on pulse periods, this study observes that the pulse periods tend to approach 1.5 times the fundamental period of the soil deposit after pulselike ground motions propagate through the soil deposit. This observation provides a useful clue to pulselike ground motion selection for soil sites.

The use of supporting fluids to stabilize excavations is a common technique adopted in the construction industry. Rapid detection of incipient collapse for deep excavations and timely decision making are crucial to ensure safety during construction. This paper explores a hybrid framework for forecasting the collapse of fluid-supported circular excavations by combining physics-based and data-driven modeling. Finite-element limit analysis is first used to develop a numerical database of stability numbers for both unsupported and fluid-supported circular excavations. The parameters considered in the modeling include excavation geometry, soil strength profile, and support fluid properties. A data-driven algorithm is used to learn the numerical results to develop a fast surrogate amenable for integration within real-time monitoring systems. By way of example, the proposed forecasting strategy is retrospectively applied to a recent field monitoring case history where the observational method is used to update the input parameters of the data-driven surrogate.

Developing a reliable, cost-effective liquefaction triggering procedure for characterizing the liquefaction potential of gravelly soils based on in situ penetration testing has always been a great challenge for geotechnical engineers and researchers. Typical correlations based on the standard penetration test (SPT) and the cone penetration test (CPT) are affected by large-size gravel particles, which can lead to erroneous results. The Becker Penetration Test, well known for gravelly soil characterization, is cost-prohibitive for routine projects and is not available in most of the world. With a cone diameter of 74 mm the Chinese dynamic cone penetration test (DPT) is superior to smaller penetrometers and can be economically performed with conventional drilling equipment. DPT has previously been directly correlated to field performance data, and probabilistic liquefaction resistance curves were developed based on one earthquake and geologic environment in China; however, the use of these data in other tectonic and geologic environments was not validated. In this study, 137 data points from 10 different earthquakes and different depositional environments in seven countries have been used to develop probabilistic liquefaction resistance curves. The data set was expanded by performing DPT soundings at sites around the world where gravelly soil did or did not liquefy in past earthquakes. Based on the expanded DPT database, a new set of magnitude-dependent probabilistic triggering curves has been developed using logistic regression analysis. The new triggering curves are better constrained by data and the spread between the 85% and 15% probability curves is reduced. Liquefaction resistance is shifted upward at lower DPT values. A new magnitude scaling factor (MSF) curve has also been developed specifically for gravel liquefaction which was found to be consistent with previous curves for sand.

Nonlinear, effective stress finite-element analyses are used to model earthquake-induced displacements at lateral spread sites near a free face. The numerical analyses consist of 132 models with model geometries selected to isolate the influence of the height of the free face, the thickness of liquefiable layers, sloping ground behind the free face, and the presence of a topographic terrace on lateral spread displacement patterns. Each model is analyzed in the context of how the geometric factors influence the maximum horizontal displacement, the inland extent of displacements, and the shape of the displacement profile between the free face and the inland extent. For sites with flat ground behind the free face and with no terrace present, the dominant factor controlling the displacement pattern is the combined thickness of the free face and underlying liquefiable soil. Lateral spread displacements are significantly affected by the presence of sloping ground behind the free face, with the inland extent affected more significantly than the maximum displacement. The presence of a topographic terrace several hundred meters from a free face can increase appreciably the displacements in the area between the free face and terrace. A bilinear surface model is proposed as a framework for predicting displacement patterns at a free-face lateral spread site and used to model the displacements from the numerical simulations. The observations in this study are based only on a single input ground motion, but the framework can be extended with additional analyses utilizing a range of earthquake ground motions.

Tailing dams are constructed to impound the byproducts of mining operations and are often built using the coarser fraction of the tailings resulting from gravity separation processes. The high stresses anticipated at the bottom of tall tailings dams can lead to grain crushing, resulting in a reduction in the hydraulic conductivity and, ultimately, long-term performance issues if the water drains at a slower rate than required. Therefore, in order to accurately evaluate the margin of safety in designing tall tailings dams, understanding the evolution of the hydromechanical behavior of the tailings is important. This paper presents the results from a series of laboratory-scale high-stress compression tests combined with hydraulic conductivity measurements using a specially designed oedometer cell. The experimental results were subsequently interpreted by an enhanced continuum breakage mechanics model. The grain-size distributions predicted by the continuum breakage model were further combined with six commonly used hydraulic models to predict the reduction of hydraulic conductivity of tailings sand subjected to grain crushing. The results suggest that a stress increase from 5 to 40 MPa can cause an increase in fines content from 11% to 17%, respectively, and a corresponding reduction in hydraulic conductivity of up to one order of magnitude for the tested materials. The paper highlights that the breakage mechanics theory combined with proper hydraulic conductivity models can offer reliable predictions of the evolution of the hydromechanical behavior of tailings sands subjected to high stresses.

A set of experimental data on the time-dependent oedometric compression behavior of sands is presented. The investigation focuses on the behavior of a clean quartz sand with respect to creep, strain-rate response, stress relaxation, and strain and strain rate history. The influence of different fine contents up to 25% by weight on creep, strain rate response, and stress relaxation are studied. The tests were conducted under vertical effective stress levels up to 7,500 kPa with specimens of medium dense and very dense relative density. The tests show a stress and density dependent creep behavior regardless of the fine content. Creep of sands with more than 14% by weight fine content can be described by a constant $C_{\alpha }/C_c$ ratio, whereas clean sand shows varying ratios. The response of the soils upon sudden changes in loading strain rate changes from clean sand, which exhibits only a temporary response of the stress-strain behavior, to the sands with more than 14% by weight fine content, which have a permanent response of the stress-strain behavior with continued straining. Stress relaxation tests show decreasing normalized stress relaxation $\sigma /{\sigma }_0$ with increasing vertical effective stress. The behavior is independent of the density. It is described by the oedometric swelling index ${\kappa }^0$. The tests on the influence of strain rate history show that the creep behavior of the sands is not dependent on it in the time scales studied.

Tunneling can compromise the safety and serviceability of existing buried infrastructure because of settlements, crack openings, dislocations, and material strains. A continuum-based soil-structure interaction model, implementing an equivalent Timoshenko beam, is used to evaluate the excavation-induced settlements and longitudinal deformations of existing tunnels and pipelines. Both single and twin tunneling scenarios are examined. The shear flexibility of shield and sprayed concrete lining tunnels may be significant. This increases tunneling-induced settlements while it decreases tilt, curvature, and the associated bending moment, with implications for optimal monitoring installations. In this work, a new dimensionless shear factor is introduced, governing the relative importance of shear and bending deformations and accounting for the settlement trough width. This can be used to evaluate if a pure-bending, shear-dominated, or mixed deformation mode should be expected. Design charts to assess existing infrastructure affected by either single or twin tunnels are proposed.

Heat transfer from/to energy piles can cause plastic contraction of soft clay with a low overconsolidation ratio (OCR) during heating and cooling. This can lead to thermally induced excess pore water pressure and changes in the lateral stress acting on a pile. These thermally induced phenomena cause additional plastic settlement of the soil and pile. Irreversible settlement may cause serviceability or ultimate limit state problems for floating energy piles whose capacity is mainly derived from shaft resistance. Due to intended operational needs or by accident, cyclic nonsymmetrical thermal loads may be applied to floating energy pile groups and piled rafts. The thermomechanical interaction among nonsymmetrical loaded piles is not well understood. In this study, a series of cyclic nonsymmetrical thermally loaded centrifuge model tests were conducted on floating pile groups and piled rafts in soft kaolin clay with an OCR of 1.7 at the pile toe. The performance of floating $2\times 2$ elevated energy pile groups and energy piled rafts was investigated. Three piles in each group were subjected to 15 cycles of $\pm 14°\mathrm{C}$ in temperature change. The thermally induced irreversible settlement and tilting of the elevated pile groups exceeded serviceability and ultimate criteria. The piled rafts similarly settled but to a smaller extent than the elevated group. Their tilting, however, did not exceed the serviceability criterion. It is recommended that energy piled rafts be used in soft clay instead of elevated energy piles.

A major concern for urban construction projects involving deep excavations is the impact of excavation-related ground movements on adjacent buildings and utilities. Consequently, stiff excavation support systems are required to execute the work. The conventional approach for designing an excavation support system is to use a limit equilibrium approach to determine the required capacity and stiffness of the excavation support system. Although this approach may provide an adequate factor of safety against structural failure, it may yield excessive system deformations and subsequent ground movements, causing nearby structures to possibly sustain damage. Thus, it is critical that design methods for excavation support systems consider the potential of induced damage in adjacent infrastructure. Current methods that consider potential damage to adjacent structures in the excavation support system design compare predicted damage to acceptable damage at the end of the support system design process. These design methodologies involve iterations of the support system characteristics until the required stiffness of the system complies with the acceptable level of damage. Any variation in the ground or adjacent structure characteristics from a previous definition may cause a complete redefinition of the support system characteristics. This paper presents a new design methodology that directly designs an excavation support system by first considering an acceptable level of damage in the surrounding facilities and estimating the corresponding ground deformations. The wall and support elements of the support system are then designed such that the system yields the limiting ground deformations. The resulting excavation support system limits damage to adjacent structures below an acceptable level and automatically satisfies the structural stability requirements. More significantly, the design of the excavation support system does not require an iterative process.

The performance of geosynthetic layered systems during their service life in terms of interface shear behavior and strength properties is of major importance in certain geotechnical applications. The interfaces between geotextiles and geomembranes in landfill applications are subject to temperature changes. In this respect, interface shear behavior requires assessment of the engineering strength properties of the components, both independently and collectively, at different temperatures. To this end, an extensive research study was undertaken to investigate temperature effects on the interface shear behavior between needle-punched nonwoven (NPNW) polypropylene (PP) geotextiles and both smooth polyvinylchloride (PVC), as well as smooth and textured high-density polyethylene (HDPE) geomembranes. A temperature-controlled chamber (TCC) was utilized to simulate the field conditions at elevated temperatures and evaluate shear displacement and frictional response mobilized at different temperatures. The physical laboratory testing program consisted of interface shear tests between material combinations found in landfill applications under a range of normal stress levels from 10 to 400 kPa and at a range of ambient temperatures from 21°C to 50°C. An increase in temperature from the standard laboratory test temperature of 21°C to an equivalent in situ temperature of 50°C increases the peak and postpeak interface friction values by a minimum of 14%. For selected combinations of materials, the amount of increase can be in excess of 20% and as high as 22%. Consequently, interface shear behavior determined at room temperature yields interface friction values that are conservative at higher temperatures.

A thermodynamics-based constitutive model is developed for calcareous sand treated by microbially induced calcite precipitation (MICP) to describe the effects of biocementation and its degradation by cyclic shearing within the framework of nonequilibrium thermodynamics. The elastic potential function implemented within the constitutive model leads to a hyperelastic representation of stress-strain-strength with considerations of true cohesion and stress-density state dependency, yielding a theoretical stress state boundary surface for sands treated with different levels of MICP. In addition, the concepts of configuration entropy and locked energy are defined to describe energy dissipation and corresponding irreversible deformation accumulated during cyclic loading. The effects of MICP treatment on the cyclic behavior of sands can be well predicted through the definition of the MICP-induced increase in soil density and a bonding parameter that varies as a function of the reaction index, representing the concentration and volume of microbial reactant. Predictions of a series of undrained cyclic triaxial tests of sands with and without MICP are made to validate the model. It is shown that a two-stage degradation of the bonding between sand particles should be considered for better predictions of the cyclic behavior. In general, the model sufficiently captures the cyclic stress-strain hysteresis and excess pore pressure generation in MICP-treated sand and gives insights into the underlying mechanisms.

Particle breakage plays a relevant role on the stress-strain behavior of rockfills. As is widely recognized, the amount of particle breakage of coarse-grained soils depends on a combination of several factors, namely grain size, mineralogy, the shape of the particles, stress level, and degree of saturation and its variation. The results of monotonic triaxial tests carried out on a large apparatus on specimens of two types of rockfills and three different gradings highlighted the role of the coefficient of uniformity, grain tensile strength, and loading path on particle breakage and overall soil behavior. Starting from experimental evidence, a simplified conceptual model to predict the level of breakage during a generic stress path was developed. Experimental data supported the hypothesis of the influence of particle breakage on the position of the critical state lines (CSLs) in the compression plane. This implies that CSL parameters are state dependent, changing with current grading modifications, and are not intrinsic. A simplified procedure for predicting the position of the CSLs as a function of current particle breakage was, therefore, developed and calibrated against laboratory test results.

This study investigated the disadvantages of existing observational methods using theoretical (radial consolidation solution) and actual (radial consolidation test with 24-h duration) settlement data. Sampling ranges taken from actual settlement data significantly affected the predicted values of ultimate consolidation settlement ($S_{\mathrm{ult}}$) and consolidation coefficient ($c_h$), in an opposite result to those of the theoretical data. Thus, the modification of the Asaoka and exponential methods and a linear-rule method are proposed to resolve such a limitation and to apply short- and long-term measured settlement data. The applicability of the proposed methods was verified further by applying the methods to two field records and comparing the monitored and back-analyzed time–settlement curves. The three actual cases indicated that as the traces of the ultimate settlement versus sampling range inclined downward, the effects of sampling range and the proposed methods on the $S_{\mathrm{ult}}$ and $c_h$ values increased. Correlations between the measured and back-analyzed time–settlement curves varied according to the characteristics of actual curves and the newly proposed methods. Therefore, applying the three proposed methods to a set of measured data and then selecting one of the predicted values is recommended for practical applications.

The mechanical behavior (strength, stiffness, and volume change) of soils depends on the stress state, which for unsaturated soils is controlled by interparticle forces in addition to the skeletal forces. The interparticle forces for an uncemented soil (i.e., adsorptive and capillary forces) are functions of saturation that are unique for each soil. Previous studies have quantified the contribution of interparticle forces to soil shear strength using the suction stress characteristic curve (SSCC) and demonstrated the initial evidence of transitions between the interparticle force components. This study quantifies the stiffness of uncemented kaolinite over a wide range of saturation in dry of optimum conditions using resilient modulus and shear modulus tests. The stiffness-saturation curves show two unique inflection points that mark (1) the transition between an adsorption-dominated water uptake regime to a capillarity-dominated water uptake regime at $\sim 0.04–0.1$ saturation; and (2) the onset of a reduction in capillary forces at $\sim 0.45–0.55$ saturation. The shape of stiffness-saturation curves is compared with the adsorptive and capillary components of SSCC and SWRC. The results provide further evidence on water uptake mechanisms and corresponding evolution in interparticle force components in compacted kaolinite, enhancing our understanding of the stiffness behavior of unsaturated soils.

Coarse grains accumulate at granular flow fronts and must be considered when studying granular flows impacting barriers. Experimental studies often use instrumented barriers comprising a load transducer and load-bearing plate. However, it is not clear how to scale the mass of these composite barriers relative to coarse grains such that forces induced are properly captured by the load transducer. This study considers the impact force from grains on instrumented barriers using both a physical flume and a discrete element method (DEM) model. Results reveal two main scaling considerations for granular flows impacting load-measuring systems: (1) the design of the load-measuring system, and (2) the model size. Considerations relating to the design of the load-measuring system include (1) the relative mass of the grains and the load-measuring system; (2) the spring element stiffness of the load-measuring system; and (3) the grain impact velocity. These are captured using a newly proposed dimensionless number. Additionally, discrete impacts appear to reduce in importance as the sizes of the flow and channel are increased, relative to the final static load due to the flow piling up, within the framework of Hertzian impact mechanics. This implies that small-scale DEM simulations adopting low elastic moduli (reducing discrete impact loads) may unintentionally correctly represent larger-scale impact dynamics.

Rock coring is an essential method of geotechnical site characterization for foundations supported by rock, in which three possible phases of operation exist: inefficient, optimized, and destructive. When operating within the optimized phase, core recoveries and the rock quality designation reflect the strata encountered. However, the optimized phase is rarely achieved in practice, leading to deficiencies in strength assessment and geotechnical site characterization. This paper identifies the operational limits that separate each phase of rock coring by using measuring while drilling (MWD) and quantifies the increased energy that results from an inadequate depth of cut (Phase 1), the effects of breaking rock particles into smaller sizes, and the damage that occurs to core specimens from increased frictional resistance (Phase 3), as well as the effect rock strength and bit geometry have on mechanical efficiency. Drilling parameter interdependencies are discussed and detailed guidelines to assess rock strength in situ via MWD are provided. Finally, recommended coring guidelines are established through MWD which optimize the quantity and quality of strength assessments collected to improve geotechnical site characterization.

The effect of overconsolidation on the monotonic shearing resistance of three nonplastic soils (a clean sand, a clean sand and fine tailings mixture, and a fine tailings) was examined using laboratory $K_o$-consolidated constant volume direct simple shear (DSS) tests performed on contractive specimens. Two different overconsolidation methods were used. Isotopically consolidated undrained triaxial compression (CIU-TC) tests from the literature also are presented. The stress history and normalized soil engineering properties (SHANSEP) equation was used to interpret the relationship between strength ratios and overconsolidation ratio (OCR). The SHANSEP equation appears to capture the increases in strength ratios, at both the peak and the critical states, with OCR. However, only the increase in undrained critical state shear strength ratio, $s_u(\mathrm{critical})/{\sigma }_{vo}^{\prime }$, with OCR can be derived based on critical state soil mechanics concepts using the swelling index, $C_s$, compression index, $C_c$, and slope of the critical state line, ${\lambda }_{10}$. In addition, theoretical derivation showed that the strength ratio increase can be affected by the method of overconsolidation, especially when $C_c/{\lambda }_{10}$ is small. Overall, the SHANSEP equation parameter $m$ obtained from the constant volume DSS and CIU-TC tests was in good agreement with theoretical values.

The paper demonstrates load and resistance factor design (LRFD) calibration for tensile strength and pullout strength limit states for steel strip mechanically stabilized earth (MSE) walls using a reliability theory-based approach. The analyses adopt load models found in current North American LRFD specifications in combination with a coupled mechanical-corrosion model for the reinforcement tensile strength and pullout models found in design guidelines and in the research literature. Resistance factors for prescribed load factors and different load and resistance model combinations are compiled in tables. The limitations of the LRFD approach to generate resistance factors that are judged to be acceptable based on current practice are demonstrated. The challenges to generate consistent design outcomes with the same margin of safety expressed probabilistically are identified, and the link to reliability-based design is described. Example designs are provided to show the impact on steel reinforcement quantities and length when using different models in combination with proposed and current specified load and resistance factors. The calibration outcomes will be of value to code writers in Canada and the US for MSE wall design sections in the next editions of national geotechnical foundation LRFD codes.

Biocemented shale soils are composite materials, and their micromechanical properties are difficult to measure using common macromechanical tests. In this work, nanoindentation tests were conducted to study the effects of microstructures, crystal types of calcium carbonate, and locations of test points on the micromechanical properties of biocemented shale soils. The transformation process of crystal types of calcium carbonate during biogrouting was revealed using scanning electron microscopy and X-ray diffraction imaging techniques. The results showed that a significant amount of voids within the cementing body were generated due to the death of bacillus pasteurii. Vaterite and calcite were both detected in the same sample, where the vaterite gradually changed into calcite during the biogrouting process. The nanoindentation tests were carried out in locations with different surrounding conditions, and the micromechanical properties of biocemented soils were obtained through analysis of the load-displacement curves. The relationships between fracture toughness, elastic modulus, and hardness were found to be linear based on our test results. The established empirical relationships help understand the correlations between micromechanical properties and also provide a useful method for the characterization of fracture toughness of biocemented shale soils.

This study presents a coupled material point method (MPM) formulation for the analysis of cone penetration in clays. The formulation is based on the generalized interpolation material point method (GIMP) variant of MPM. A single material point is used to represent both the soil matrix and water. The governing equations are solved using an explicit scheme with the velocity of the soil matrix and the velocity of water as the primary variables. Incompressibility constraints in the soil matrix are resolved using the nonlinear B-bar method, and pore pressures are computed at element centers. The formulation is validated through problems for which analytical or numerical solutions are available. Cone penetration resistances measured at a Boston Blue Clay (BBC) test site are then computed using the coupled MPM formulation with the constitutive response of BBC captured using an advanced bounding surface model based on critical state soil mechanics. Based on the cone penetration simulation, the penetration resistances under undrained, partially drained, and drained conditions are computed by varying the hydraulic conductivity of the clay. The cone factor for undrained penetration is also calculated. Verification and validation exercises demonstrate the efficacy and robustness of the adopted formulation in the realistic simulation of cone penetration in clay.

The effect of the loading frequency on the volumetric strain accumulation, stiffness improvement, and damping ratio of silica sand during cyclic shearing of the silica sand was investigated by performing drained cyclic strain-controlled direct simple shear tests. Cyclic shear strain amplitudes (${\gamma }_c$) of 0.5% and 1.0%; vertical effective stresses (${\sigma }_{v0}^{\prime }$) of 100, 200, and 300 kPa; and loading frequencies ($f$) of 0.05, 0.1, 0.5, and 1 Hz were considered. Sand samples were prepared in the loose ($D_r=40\%$) and dense ($D_r=80\%$) states using dry Nakdong River sand. For loose sand tested at ${\sigma }_{v0}^{\prime }=100$ and 200 kPa, the test results showed that the rate of volumetric strain accumulation decreased with increasing $f$, and the decrease was independent of ${\sigma }_{v0}^{\prime }$ and more obvious at the higher ${\gamma }_c$ value. The maximum decrease in the volumetric strain accumulation was 60%, which corresponded to a 20-fold increase in $f$, from 0.05 to 1 Hz. For dense sand tested at ${\sigma }_{v0}^{\prime }=300\mathrm{kPa}$, the accumulated rate of volumetric strain was essentially identical, especially at ${\gamma }_c=1.0\%$. The shear modulus ratio always increased with the increase of $f$ for both loose and dense sand, but the difference between shear modulus ratios at different $f$ was reduced with the increase of ${\sigma }_{\mathit{v}0}^{\prime }$, when the samples were sheared at ${\gamma }_c=1.0\%$. The improvement parameter $t$, which is proposed in this study and which represents the increase in the rate of cyclic stiffness with the number of cycles ($N$), increased linearly with $f$. For loose sand, it increased by approximately 56% and 12% at ${\gamma }_c=0.5\%$ and 1.0%, regardless of ${\sigma }_{v0}^{\prime }$, respectively. The normalized damping ratio (${\lambda }_n$) was independent of $D_r$, ${\sigma }_{v0}^{\prime }$, $f$, and ${\gamma }_c$, and the relationship between ${\lambda }_n$ and $N$ was well expressed by a power function. The effect of the loading frequency on Nakdong River sand inferred from a drained test was similar to that indicated by an undrained test.

Geophysical data play a vital role in offshore site characterizations, especially during the planning phase of the geotechnical investigation, in order to define the scope to be performed at the site most effectively, but also to aid interpretation once geotechnical data are acquired. Although geophysical data are advantageous in imaging the subsurface conditions over large offshore areas and can reveal important information about seabed features and the sediment depositional history, the information obtained is usually qualitative from a geotechnical perspective. In today’s practice, the engineering properties of soils for design purposes are determined by established ground-truth methods (e.g., offshore sampling, seabed drilling, and in situ testing, among others) applied directly at locations of proposed infrastructure. However, recent advances in seismic acquisition and interpretation methods, machine learning algorithms as well as computational power, provide opportunities to fully integrate geophysical and geotechnical (G&G) data in a digital format to quantitatively assess the site variability and design parameters with limited geotechnical data. Therefore, the motivations of this paper are to advance the quantitative G&G integration to benefit the broader engineering community and to provide thoughts on improving this technique for industrial applications. The scope of the paper is to demonstrate a successful G&G integration workflow that mainly consists of acoustic impedance inversion on ultrahigh–frequency ($>\mathrm{2,000}\mathrm{Hz}$) geophysical data, and the integration with cone penetration test (CPT) data using artificial neural networks to create synthetic CPT profiles. The proposed workflow has been blindly tested and satisfactory results are achieved for predicting the CPT profiles when compared with the actual data.

A life-cycle sustainability assessment evaluated and compared the impacts of five ground improvement methods commonly implemented to mitigate liquefaction: compaction grouting, deep dynamic compaction, deep soil mixing, vibro compaction, and vibro replacement (i.e., stone columns). Using typical scopes of work provided by geotechnical contractors who specialize in ground improvement, this study developed sustainability benchmarks for the life-cycle impacts and costs of each method, quantified the consequences of the risk and uncertainty inherent in ground improvement projects, and examined impacts to land and soil resources that occur throughout the life cycle. Results showed that deep soil mixing and compaction grouting are the most impactful and costly methods due to the use of portland cement, an energy- and emissions-intensive material. Vibratory methods and deep dynamic compaction are more sustainable, despite the fact that their impacts and costs are more variable and uncertain. Although many factors influence ground improvement design selection (e.g., safety, performance criteria, feasibility, and cost), the results of this study may help inform decision making to realize more sustainable infrastructure.

Stress path tests in plane strain (PS) conditions with varying stress ratios have been carried out using a newly developed flexible boundary (FB) multiaxial testing device. It employs electro-pneumatic control and allows the application of independent principal stresses on each face of a 96-mm cubical soil specimen through a closed-loop feedback control system. Different stages of testing have been automated for both deformation and stress-controlled loading. It also has provisions for local deformation field estimation from the images acquired on the transparent rigid PS boundary. The friction angle for different stress paths in compression and extension mode is found to have minimal variation in PS conditions. The experimentally observed yield points match well with a simplified two-dimensional (2D) yield criterion resembling the shape of a “tear-drop.” Local shear strain profiles under FB-PS conditions imply nearly uniform material behavior, while the emergence of instabilities is found to be minimal and mostly at the specimen corners.

The Canterbury Earthquake Sequence produced a spatial pattern of liquefaction-induced surface ejecta at an open field along Palinurus Road in Christchurch, New Zealand, that would not be expected based on simplified liquefaction evaluation procedures. Half the site discharged sand boils and the other half did not. Two-dimensional fully-coupled nonlinear dynamic analyses (NDAs) were performed to examine why simplified one-dimensional liquefaction vulnerability indices (LVIs) overestimated liquefaction manifestations at this site for the 2010 Darfield and 2011 Christchurch earthquakes and did not distinguish between areas with and without surface ejecta. The NDAs use the PM4Sand and PM4Silt constitutive models for sand-like and clay-like portions of the subsurface, respectively, within the Fast Lagrangian Analysis of Continua (FLAC) finite-difference program. Material parameters are obtained from in situ geophysical and cone penetration test (CPT) data. A sensitivity study is performed to assess the influence of (1) representative soil property selections and the use of a CPT inverse filtering procedure to correct for thin-layer and transition zone effects, (2) ground motions developed by two distinct methods (i.e., recordings and physics-based simulations), and (3) model assumptions affecting diffusion during reconsolidation. Ground deformations and flow patterns during and after ground shaking are examined. The results provide insights on how stratigraphic details and other factors can affect the system response and dictate the degree and extent of liquefaction surface manifestations.

The application of geostatistical analyses of site investigation data for tunneling projects has gained significant attention in the literature. While the proposed techniques are useful for modeling the spatial variability and uncertainty in subsurface conditions, the extension of these techniques to the mitigation of critical tunneling risks in soils is limited. This paper demonstrates how a geostatistical approach can be used to characterize cutter tool wear and cutterhead clogging, two critical risks associated with mechanized tunneling in soils. A case study using data from the Seattle Northgate Link tunnel project is presented and validated by actual construction data reported. The results demonstrate that the proposed approach provides significantly more accurate prediction of the necessary mitigation measures than the conventional deterministic approach, providing significant estimated cost savings with a 40%–42% reduction in estimated tool replacements and a 17% reduction in estimated conditioning volume for this project.

Excess pore water pressure (EPWP) development and decay due to the installation and static loading tests of controlled modulus columns (CMC) in soft soil was measured with piezometers equipped with low air entry (LAE) filters and a piezocone (CPTU) equipped with a high air entry (HAE) filter. The HAE filter allows for detailed detection of EPWP in short time intervals during construction of CMC. The influence zone due to the installation of the CMC group extends up to 40D (D = column diameter) with significant installation effects and high EPWP within the zone of 7D. The influence zone during the static loading test is much narrower and does not exceed 2D. The presented research shows the applicability of using a CPTU in EPWP monitoring during CMC construction and clarifies some effects of CMC group installation.

Multidirectional cyclic shearing induced by earthquakes involves variations not only in amplitude but also in direction. To investigate the undrained cyclic shear responses of sand under this complex stress state, several series of simple shear tests were conducted on reconstituted Toyoura sand specimens prepared by water sedimentation and dry deposition methods, at the relative density of about 34% and initial vertical stress of 100 kPa, with the variable-direction dynamic cyclic simple shear system. By applying cyclic stresses in two mutually perpendicular horizontal directions with a certain phase difference, the multidirectional complex cyclic stress path was achieved. The cyclic unstable behavior, pore pressure response, and liquefaction resistance were analyzed with varying phase differences. Results indicate that the increase of phase difference delays the occurrence of unstable cyclic response. The development trend of normalized pore pressure is not affected by the phase difference or sample preparation method. A modified pore pressure generation model is developed to quantify the normalized pore pressure development of sand. Moreover, the effect of phase difference on liquefaction resistance is not monotonic. The liquefaction resistance of sand under multidirectional cyclic loading is approximately 70% of that under unidirectional cyclic loading. Also, the liquefaction resistance of specimens formed by dry deposition is less than that of specimens formed by water sedimentation.