Journal of Geotechnical and Geoenvironmental Engineering

Seismic piezocone data obtained from Banks Peninsula loess soil sites in the Port Hills south of Christchurch, New Zealand, are used with multiple linear regression to develop a new Banks Peninsula loess-specific $\mathrm{CPT}\text{-}{V}_s$ correlation for predicting shear wave velocity ($V_s$) from cone penetration test (CPT) measurements. The need for this new correlation is demonstrated through comparisons with existing $\mathrm{CPT}\text{-}{V}_s$ models, including a recently developed Christchurch-specific general soils model, with the loess $V_s$ measurements. It is shown that the existing general soil $\mathrm{CPT}\text{-}{V}_s$ models tend to systematically underpredict the loess $V_s$, and it is demonstrated that this underprediction is due to fundamental differences in how the properties of loess and general soil types affect both CPT measurements and shear-wave velocity, and that aging effects alone cannot account for the observed differences.

This paper reports a measure for easing spudcan-footprint interactions when a jack-up rig needs to be installed near existing jack-up footprints. Two novel spudcan shapes, a skirted spudcan with four rectangular holes and a skirted spudcan with six circular holes and sloped bottom profile, were investigated using 3D large deformation finite-element (LDFE) analyses. The LDFE analyses were performed using the coupled Eulerian-Lagrangian (CEL) approach in the commercial finite-element package ABAQUS. After displaying the validity of the analyses against existing LDFE results and centrifuge test data, the efficiencies of the novel spudcans were studied against a generic spudcan shape, including the effects of spudcan offset distance from the footprint and the footprint depth. Both soft and stiff seabed strength profiles were considered, with the undrained shear strength increasing with depth. The potential of the spudcan sliding toward the footprint center during installation was evaluated based on the resultant maximum horizontal force ($H_{\mathrm{ma}\mathrm{x}}$) and moment ($M_{\mathrm{ma}\mathrm{x}}$) acting on the different spudcans. It is found that, between the two novel spudcans, the spudcan with six holes and sloped bottom profile is more effective at reducing $H_{\mathrm{ma}\mathrm{x}}$ and $M_{\mathrm{ma}\mathrm{x}}$. Any reduction in the resultant horizontal force on the spudcan can generate a large reduction of the moment at the top of a long jack-up leg. The results from this study indicate that the novel spudcan with circular holes and sloped bottom profile has the potential to ease spudcan-footprint interactions without any additional mechanical operations.

Empirical design methods for stone-column foundations are often on single stone columns or as a homogeneous medium of soil and column. These methods underestimate the capacity of the composite system because they do not take into account the increased confining stress acting on the stone column or the increased stiffness of the soil. This study used PLAXIS 2D to study the effect of the installation method on the confining pressure and soil stiffness around a single column by assuming the installation of the column could be modeled as an expanding cavity followed by consolidation of the surrounding soil. The mean stress and stiffness generated during installation between two adjacent columns was used in PLAXIS 3D to compare the settlement of circular foundations on estuarine deposits reinforced by stone columns at a site in Santa Barbara, California. Good agreement was found between the predicted and actual settlement of the trial foundations on three column arrangements. The predictions gave a better estimate of the settlement compared with those using a unit cell or homogeneous medium, showing that improvements to the soil should be taken into account when assessing stone-column performance.

Waste glass is a solid residue widely available in the urban centers, where it is discarded after being used in the most diverse applications (container for distinct products, tableware, decorative objects, civil construction, and the automobile industry). Carbide lime is a by-product from the manufacture of acetylene gas. This study evaluates the potential of combining these two wastes, finely ground waste glass and carbide lime, as a possible hydraulic cement (substituting portland cement) to enhance soil behavior. Such blends, when compacted, have potential application in earthworks such as beds of pipelines and spread footings, as well as base/subbase of pavements. Pozzolanic reactions occur between silica in amorphous phases (in ground waste glass) and ${\mathrm{Ca}}^{++}$ (in carbide lime) in an alkaline environment. The impact of the ground glass and the carbide lime content, as well as the dry unit weight, on the properties (strength, stiffness, and durability) of compacted sandy soil–ground waste glass–carbide lime mixes is quantified, where two soils have been used, Osorio sand and a clayey sand, Botucatu residual sandstone (BRS). A novel parameter, named the porosity/binder index ($\eta /B_{iv}$), allows normalizing the behavior of the unconfined compressive strength ($q_u$), the shear modulus at small strains ($G_0$), and the accumulated loss of mass (ALM) (after wetting-drying cycles) of the sandy soil–ground waste glass–carbide lime mixes, considering ground glass plus carbide lime as binder. Results have shown similar trends among $q_u$, $G_0$, and ALM with $\eta /B_{iv}$ for the two studied sandy soils–ground glass–lime mixes, even though each was cured at an ambient temperature ($23\pm 2°\mathrm{C}$), but considering different curing periods (7 days for the former and 180 days for the latter).

Gabions are the most commonly adopted cushion layer for shielding rigid debris-resisting barriers against boulder impact. Despite the prevalent use of gabions, they comprise heavy rock fragments that are not easily transported up steep natural terrain. The advent of using light-weight cellular glass as an alternative cushion layer provides an innovative approach for absorbing impact energy. However, a lack of insight on their load attenuation characteristics has hindered its potential implementation. In this study, cellular glass was subjected to successive impacts to replicate the dynamic loading of boulders by using a large-scale pendulum setup. Results reveal that for a single impact at 70 kJ, crushing exhibited by cellular glass leads to 25% lower impact force compared to gabions, which rely predominantly on rock fragment rearrangement to absorb energy. However, gabions exhibit more effective load spreading, with a diffusion angle three times greater than cellular glass. To ensure robust designs for cellular glass, the Johnson’s damage number is proposed to quantify the plastic deformation and to improve estimates of the cushioning efficiency represented by the load-reduction factor ($K_{\mathrm{c}}$) used in current design.

This paper considers a hydrostatic–seasonal–time (HST) statistical model for predicting the settlement behavior of a concrete-faced rockfill dam (CFRD) during operation. The constituents of the model are innovatively related to viscoelastic–plastic material model components, with the novel addition of considering unloading–reloading behavior when determining the model parameters. The statistical model developed considers both load-related and time-related deformation behavior of rockfill and CFRDs. The discussion compares different functions from the literature describing time-dependent deformation of rockfill dams and CFRDs and emphasizes cautious selection of predictors to enhance any statistical model’s credibility. The model is applied to the case of the 200-m-high Kárahnjúkar CFRD. The aim of the statistical analysis is first to create a prediction model for short- and long-term settlements of the dam, and second to extract behavioral patterns for structural-health monitoring applications. This is important for the operational safety of large dams, and thus the resilience and sustainability of related civil infrastructure systems.

Undrained and drained triaxial compression tests were simulated using the discrete element method (DEM). It was found that the transition states between contractive and dilative behavior of dense specimens, that is, the characteristic (Ch) and phase transformation (PT) states for drained and undrained conditions, respectively, are the same state in terms of stress ratio and fabric quantity ($F_{vM}$). The transition was not due to the change in number of particle contacts, that is, coordination number ($CN$). A unique critical state (CS) line was obtained for a large range of mean effective stresses ($p^{\prime }$) for both drained and undrained simulations, which facilitates further analysis in term of the state parameter ($\psi$). Because PT, Ch states, and CS were representative of sand behavior, the SANISAND model was adopted to predict DEM simulations. Despite some limitations, the model can predict overall trends of shearing response and produce adequate qualitative behavior such CS, PT, or Ch states of DEM simulations.

Several emerging problems in geotechnical and geoenvironmental engineering pose multiphysics problems involving nonisothermal processes in unsaturated soils. Properly studying these problems requires the development of models for the soil water retention curve (SWRC) to describe the constitutive behavior of unsaturated soils under nonisothermal conditions. This study aims to develop analytical expressions of nonisothermal SWRCs. Closed-from expressions are presented to consider the effects of temperature on adsorption and matric suction in unsaturated soils. The formulation for the nonisothermal matric suction accounts for the effects of temperature on the surface tension, soil–water contact angle, and adsorption by the enthalpy of immersion per unit area. The formulations are then used to extend several existing isothermal SWRCs to nonisothermal conditions. The extended SWRC models are used in a parametric study to examine changes in adsorbed water, capillary water, and total water content versus matric suction for Ottawa sand and Wyoming bentonite subjected to several temperatures ranging from 25 to 100°C. The results show that temperature can have significant effects on SWRCs, depending upon the soil type and range of temperature. Further, the results obtained from the proposed formulations are compared against three independent laboratory test results and very good agreement is observed with the tests conducted on sand, silt, and clay under different temperatures. The proposed formulations can be readily incorporated into analytical solutions and numerical simulations of thermo-hydro-mechanical models of unsaturated soils. The findings of the study can facilitate using numerical models to simulate various nonisothermal applications involving geo-energy systems and soil-atmospheric interaction problems.

This paper presents an analytical solution for the effect of tunneling-induced ground displacements on buried pipelines within an elastic continuum. The greenfield ground displacement is decomposed into an infinite series of trigonometric functions. The response of the soil and the pipeline to these trigonometric functions is then established and used to derive a solution for the global pipeline response using the superposition principle. The approach is used first with the commonly used barrel load for interaction between the pipe and the soil, under the requirement for longitudinal soil–pipe compatibility. To avoid the a priori assumption of barrel load interaction forces, the solution is then extended to consider a more general interaction load pattern based on the requirement for cross-sectional compatibility (in addition to the longitudinal compatibility). This is achieved by an additional Fourier series expansion describing the load variation along the pipe cross section. The cross-sectional Fourier expansion is solved as a minimization problem to achieve the compatibility. Previous solutions of the elastic continuum problem involved discretization along the pipeline (or the use of shape functions) with compatibility requirements at specific points, without any requirements for exact longitudinal and cross-sectional compatibility, as in the present solution. The derived solutions are presented in a normalized manner and compared with previous solutions. Various aspects of the present and previous solutions are discussed and examined.

This paper presents results from an experimental study on the undrained behavior of sand–structure interfaces subjected to cyclic undrained torsional shearing. The goals of the study are to develop understanding of the response of sand subjected to cyclic torsional loading and to develop a theoretically sound and scale-sensitive framework for interpretation of results. The results characterize the effects of initial void ratio, confining stress, surface roughness, particle angularity, and imposed loading conditions (i.e., torsional versus axial shearing). The responses of all specimens subjected to torsional shear, including those prepared at high relative density, were dominated by contractive tendencies characterized by significant excess pore-water pressure generation. Mechanisms for excess pore-water pressure generation based on experimental evidence of local volume-change tendencies at various locations within the specimens are presented. Torsional interface shearing consistently generated pore-water pressures at faster rates than axial shearing, making the former more efficient for studying cyclic soil behavior. Implications of the results of this study on the deployment of a proposed soil characterization tool are discussed.

Based on a detailed investigation of decomposed volcanic soils from Hong Kong, an extensive analysis has been made of the best approaches for prediction and description of the behavior of the decomposed volcanic rocks, materials that are commonly encountered by practicing engineers worldwide. The parameters considered were compressibility, strength, and in situ specific volume, and the indices considered were plasticity, a grading descriptor (fines content), mineralogy (clay minerals and quartz), and chemical weathering indices. The sampling depth and chemical weathering indices are the most appropriate factors to predict the compressibility of the decomposed volcanic rocks. The strength will be satisfactorily predicted by fines content, clay minerals, plasticity, and chemical weathering indices, whereas the depth, plasticity, and chemical weathering indices are most appropriate for predicting the in situ specific volume. The various approaches (depth, fines, mineralogy, plasticity, and chemical weathering indices) are each suitable for different parameters and are therefore recommended for practicing engineers working on these geomaterials, depending on which properties are needed.

Dense granular columns are often used as a liquefaction mitigation measure to (1) enhance drainage; (2) provide shear reinforcement; and (3) densify and increase lateral stresses in the surrounding soil during installation. However, the independent influence and contribution of these mitigation mechanisms on the excess pore pressures, accelerations (or shear stresses), and lateral and vertical deformations are not sufficiently understood to facilitate a reliable design. This paper presents the results of a series of dynamic centrifuge tests to fundamentally evaluate the influence of dense granular columns on the seismic performance of level and gently sloped sites, including a liquefiable layer of clean sand. Specific consideration was given to the relative importance of enhanced drainage and shear reinforcement. Granular columns with greater area replacement ratios (${\mathrm{A}}_{\mathrm{r}}$), for example ${\mathrm{A}}_{\mathrm{r}}$ greater than about 20%, were shown to be highly effective in reducing the seismic settlement and lateral deformations in gentle slopes, owing primarily to the expedited dissipation of excess pore water pressures. The influence of granular columns on accelerations (and therefore, the shear stress demand) in the surrounding soil depended on the column’s ${\mathrm{A}}_{\mathrm{r}}$ and drainage capacity. Increasing ${\mathrm{A}}_{\mathrm{r}}$ from 0 to 10% was shown to reduce the accelerations across a range of frequencies in the surrounding soil due to the shear reinforcement effect alone. However, enhanced drainage simultaneously increased the rate of excess pore pressure dissipation, helping the surrounding soil regain more quickly its shear strength and stiffness. At short drainage distances or higher ${\mathrm{A}}_{\mathrm{r}}$ values (for example, 20%), this could notably amplify the acceleration and shear stress demand on soil, particularly at greater frequencies that influence PGA. The experimental insight presented in this paper aims to improve our understanding of the mechanics of liquefaction and lateral spreading mitigation with granular columns, and it may be used to validate the numerical models used in their design.

This paper presents an analytical framework for the stability analysis of unsaturated soil slopes under rainfall. The conventional log-spiral upper bound limit analysis for dry and saturated soil slopes is extended to unsaturated soil slopes by incorporating matric suction and rainfall infiltration. For an unsaturated soil slope under rainfall, shallow translational failure may be more critical than rotational failure. Hence, a translational failure mechanism in the context of upper bound plasticity theory is proposed, and its effectiveness is validated by finite-element analysis. Through the dimensionless stability charts developed by the upper bound limit analysis, the controlling factors on the failure mode of unsaturated soil slopes under rainfall are identified and investigated.

Internal erosion processes in earth structures and their foundations may increase the failure risk of such structures. Suffusion, one of the main internal erosion processes, selectively erodes the fine particles that move through the voids formed by the coarser particles. In literature, several suffusion susceptibility investigations were already published with various tested specimen sizes. However, the influence of the specimen size on suffusion susceptibility is not well established. The objective of this study is to investigate this influence by comparing results of suffusion tests performed on six different soils, with two different sized devices. First, this study highlights the complexity of the suffusion process, which is a combination of three processes: detachment, transport, and possible filtration of the finer fraction. The results also show a decrease of the critical hydraulic gradient with the size of the specimen. The proposed interpretative method is based on the energy expended by the seepage flow and the cumulative loss dry mass. This method permits one to obtain the same suffusion susceptibility classification for both specimen sizes.

Railway industries are placing greater emphasis on implementing fast and heavy haul corridors for bulk freight and commuter transport in order to deliver more efficient and cost-effective services. However, increasing dynamic stresses from the passage of trains progressively degrades and fouls the primary load-bearing ballast layer, which inevitably leads to excessive settlement and instability, damage to track elements, and more frequent maintenance. Ballasted tracks are subjected to even greater stresses and faster deterioration in sections where a reduced ballast thickness is used (e.g., bridge decks) or at locations where heavier concrete sleepers are used instead of lightweight timber sleepers. The inclusion of under sleeper pads (USPs) at the base of a concrete sleeper is one measure used to minimize dynamic stresses and subsequent track deterioration. In this study, cyclic loads from fast and heavy haul trains were simulated using a large-scale process simulation prismoidal triaxial apparatus (PSPTA) to investigate the performance of ballast improved by USPs. The laboratory results indicate that the inclusion of an elastic element at the harder interface of the concrete sleeper–ballast reduces the stresses transmitted to the ballast and the underlying layers and minimizes the amount of deformation and degradation of the ballast. A three-dimensional finite-element model was used to predict the behavior of ballast, and the influence of USPs on the stress–strain responses of ballast generally agree with the experimental findings.

This paper presents an analytical solution for the wave-induced dynamic response in a poroelastic seabed. The water waves are described by linear wave theory. The seabed was modeled using Biot theory, where the inertia effects and compressibility of solids and fluids are considered. Based on the appropriate boundary conditions, the closed-form solutions of displacements, effective stresses, and excess pore pressure were obtained for a seabed of finite/infinite thickness. The correctness and accuracy of the proposed method were verified by comparisons with the existing analytical solutions and experimental data. Using the solutions obtained, a parametric study was carried out to examine the effects of the properties of water waves and seabed on the dynamic response of seabed. The numerical results indicate that the seabed response is significantly affected by several pertinent parameters of water waves and seabed, including wave period, water depth, pore fluid compressibility, soil permeability, shear modulus, Poisson’s ratio, seabed thickness, and so on.

This paper presents the results of forced and free horizontal vibration tests conducted on 9.0-m long and 324-mm shaft diameter single and double-helix large-capacity helical piles as well as a driven steel pipe pile of the same geometrical properties. The soil static and dynamic properties were determined from field and laboratory testing. Forced vibrations involved excitation forces with varying amplitudes. The experimental results provided insights into the dynamic pile–soil interaction for large-capacity helical piles installed in structured clayey soils. The dynamic behavior of helical piles was essentially similar to that of the driven pile, with insignificant effect from helices. The piles exhibited slight to moderate nonlinear behavior. An equivalent-linear analytical model of the pile–soil system was developed incorporating an annular zone around the pile with reduced shear modulus and accounting for pile–soil separation. The results from the model agreed well with the measured responses.

Although thermal conductivity is a widely applied parameter in geotechnical engineering, the effect of soil gradation on the thermal conductivity is not well understood. Thermal needle tests were performed to analyze the influence of gradation on the thermal conductivity of carbonate sands. The thermal conductivity of carbonate sand specimens having different gradations prepared to three void ratios was observed to increase with uniformity coefficient or fractal dimension. Although an increase in void ratio leads to a decrease in thermal conductivity, the percent difference in thermal conductivity is independent of the initial void ratio. A maximum increase in thermal conductivity of 13.9% was observed for uniformity coefficients ranging from 2 to 20. Empirical equations using the uniformity coefficient are proposed to quantify the gradation-dependent thermal conductivity of carbonate sand for use in the design of insulating layers.