International Journal of Geomechanics

A buried bucket foundation combined with a vertical truss is a new foundation system for photovoltaic farms in marine tidal flat (MTF) areas with deep soft soil. This paper employs numerical methods to study the response of the new buried bucket foundations in MTF clay under combined loading conditions. The ultimate limit states under combined static loads in the operation phase are presented as failure envelopes expressed in terms of geometric variations of foundation length and overburden soil depth, soil properties of MTF clay, and applied loads. A parametric study was carried out, and a soil failure mechanism was found from numerical studies for the newly proposed bucket foundations in MTF clay under general loading. A design method was established, which can be used for preliminary assessment of the bearing capacities of buried bucket foundations under combined loading conditions.

Helical anchors are receiving more attention these days due to their economic and environmental advantages. However, the behavior of these structures requires further investigation. One of the critical areas requiring further attention is their failure mechanism under monotonic loading conditions. This study presents the results of centrifuge testing of half-models of helical anchors behind a Perspex window, performed to visualize the failure mechanism of screw anchors using particle image velocimetry analysis. The density change that is a result of installation disturbance was simulated by a novel technique. The results showed that embedment depth had a great influence on the failure mechanism of the anchors. The critical embedment depth ratio determined was H/D = 4–5 that separated the shallow and deep behavior of the anchors. Soil was mobilized as a reverse truncated cone in the shallow mode, while a flow-around mechanism was formed in the deep mode. The inclination of the mobilized zone on both sides of the helix was close to the critical state friction angle (29°) in shallow mode. The inclination of the failure surface was related to the dilation angle of the sand in the deep mode. A minimum distance of 3D was recommended to minimize the interaction of adjacent helical plates in a multihelix anchor. In addition, a distance of 4D was suggested to minimize the interaction of adjacent helical anchors in a group.

Understanding the shear strength and failure mechanism of a rock joint is essential in rock engineering. This study performed a series of direct shear tests and discrete element modelings on artificial joint specimens to investigate the effect of roughness [randomly generated joint profiles with joint roughness coefficient (JRC) = 20, 19.6, and 10] on the joint strength. The results of the numerical simulation were consistent in the peak shear strength with the laboratory tests and Barton’s equation. From a microscopic viewpoint, the rock joint’s peak and residual shear strength were mainly mobilized from the friction property of such a joint profile. The contribution of friction to the shear strength at the residual stage was reduced because of dilation behavior and decreasing contact area along the joint surface. Therefore, the mobilized friction angle decreased from the initial basic friction angle to a certain value depending on the initial JRC value. The mobilized JRC of a rock joint was found to be related to the initial JRC, the unconfined compressive strength (UCS) of joint material, and the applying normal stress. The surface of joint models with high UCS is less damaged than that with low UCS. Finally, a new model for predicting the residual shear strength of a rock joint was also proposed, which can be applied for the joint using both randomly generated profiles and Barton’s standard profiles.

In the absence of high-quality soils, the rigid inclusion reinforcement technique has been extensively used in geotechnical engineering practice to meet the serviceability requirements of construction projects. This article aims to investigate the behavior of a single footing placed on soft soil reinforced by four rigid inclusions using three-dimensional (3D) finite difference modeling (FDM). A set of full-scale experimental tests are used as references for the development of the numerical approach. The concurrence of the numerical and experimental data allows us to assess the load transfer platform thickness influence on the system under centered and eccentric loading conditions. Some preliminary insights can thus be obtained based on this analysis for the soft soil improvement using rigid inclusions at the design stage.

Deep mixing method has been widely used to improve soft soils by increasing bearing capacity, reducing total and differential settlements, and enhancing stability. Experimental and numerical studies have demonstrated that the inclusion of deep-mixed (DM) columns in soft soils (e.g., clays and silts) could accelerate the consolidation of soft soils. Existing theoretical solutions for calculating the consolidation degree of DM column-improved soft soils are mostly complicated and not easy to use for practical applications. Therefore, a simple analytical solution is needed to calculate the consolidation degree of DM column-improved soft soils. In this study, a unit cell concept was used to develop a simplified method for calculating the consolidation degree of DM column-improved soft soils under a rigid footing. The simplified method considers the stress transfer between columns and their surrounding soil under elastic conditions and the vertical drainage of columns and their surrounding soils. The proposed simplified method is verified after compared with the numerical analysis considering four key influence factors on the consolidation degree of DM column-improved soft soils. The key influence factors include the soil thickness to unit-cell diameter ratio, the area replacement ratio, the modulus ratio of DM columns to soil, and the permeability ratio of DM columns to soil. The proposed simplified solution also captures the characteristics of the consolidation behavior of DM column-improved soft soils by considering stress transfer between columns and soil during consolidation and is easy to use in practice. Three existing analytical solutions are used for the comparisons with the proposed method. Among these methods, the proposed method has the best estimation of the consolidation degree for the DM column-improved soft soils under most conditions. It is recommended that the proposed method should be used for the condition where column permeability is close to soil permeability.

This study evaluates the unconfined compressive strength (UCS) behavior of biopolymer-modified cohesive soil exposed to natural field conditions. Two biopolymers, xanthan gum (G₁) and guar gum (G₂), at dosages of 0.5, 1, 2, and 4%, are considered for the study. The performance of biopolymers under natural curing simulates the field conditions better. To assess the stability of biopolymer-modified soil, UCS specimens were subjected to daily variations in temperature and relative humidity, for curing periods of 7, 14, 28, 45, and 60 days. UCS test results indicate that the dehydration caused due to natural curing resulted in a significant increase in UCS, owing to the crosslinking of individual soil particles with hardened biopolymer for both G₁ and G₂. The effects of dosages of G₁ and G₂, as well as curing period, on UCS are represented by multivariate regression equations based on experimental data collected after the employed curing periods. The influence of the curing period on UCS of untreated cohesive soils is also provided using nonlinear regression equations. The dosages of G₁ and G₂ required to stabilize the cohesive soils for curing periods of 7 and 28 days for the construction of embankments are computed using deterministic design and target reliability-based design optimization (TRBDO). The results obtained using these approaches reveal that the factor of safety and reliability index against UCS failure of embankment increases significantly with the increase in G₁ content from 0.5% to 4%. On the contrary, when the cohesive soils are blended with G₂ with a dosage of 0.5% to 2.9%, the factor of safety and reliability index continued to increase significantly. However, the addition of G₂ beyond 2.9% reduces the factor of safety and reliability index considerably. The results indicate that the optimum dosage of G₂ is 2.9%. The TRBDO provides a reasonable and systematic procedure for the optimum design of embankments for biopolymer-blended cohesive soils.

Even though the mechanical behavior of granular soil–rubber mixtures has attracted significant attention and promising applications in geotechnical engineering, less attention has been paid to the influence of creep and long-term response of these composites. The present study examined the compression behavior of two types of sands mixed with recycled granulated rubber with emphasis on the influence of rubber percentage and sand grain type, providing in this way some new insights with emphasis on creep influences. One natural material is composed of Leighton Buzzard quartz sand of noncrushable grains, and the second material is composed of completely decomposed granite of crushable grains (note that the terms crushable and noncrushable refer to the range of maximum overburden pressures applied in the study that ranged from 0.3 to 6.7 MPa). The influence of creep on the compression behavior of the samples was associated with the location (or not) of the pure sand and their mixtures on the normal compression line (NCL) when creep deformations were evaluated. In specific, the rate of creep deformation was found to be independent of the stress level as long as the sample had reached its NCL during compression. Even though for LBS–rubber, there was a clear decrease of the stiffness of the mixtures expressed with the constrained modulus, this was not the case for the CDG–rubber mixtures, and within the scatter of the data, the ratio of creep index to compression index fell in a relatively narrow range (0.005–0.05), suggesting that the creep deformations could be predicted based on conventional oedometer tests with short-term measurements of the applied normal stress.

The simulation of granular soil using advanced soil models relies on the precise determination of model parameters from laboratory or field experiments, or both. Although it is well known that sample reconstitution influences the stress–strain response of granular soil, the effect of different reconstitution methods on the calibration of advanced soil models has not been previously comprehensively addressed. In the present study, a hypoplastic model was calibrated from geotechnical laboratory tests on Cuxhaven sand samples. Triaxial tests were performed on samples having been reconstituted by three different methods: moist tamping, vacuum pluviation, and horizontal vibration. The influence of different reconstitution methods on the simulation performance of the hypoplastic model was quantified through three scenarios of increasing complexity: (1) stress–strain behavior in representative element volume (REV), that is, triaxial tests; (2) in situ plate load test (PLT); and (3) laboratory cone penetration test (CPT). The latter two are typical examples of boundary value problems with different strains and stiffnesses. The adopted reconstitution methods significantly affected the REV simulation at high relative density of both peak friction angles and peak dilation angles. The reconstitution methods have a limited effect on boundary value problem simulations, being moderate for PLTs and small for CPTs. The influence of stiffness (intergranular strain) parameters on simulation results increased from REVs (no influence detected), over boundary value problems with low strain and stiffness (PLTs) to boundary value problems with high strain and stiffness (CPTs).

It is very important to accurately calculate the frost heave force for the frost resistance design of tunnels in cold regions. A computational model will divide the lining and surrounding rock into eight parts, such as the support zone, the frozen zone (e.g., isothermal Rings I, II, III, IV, V, and VI), and the unfrozen surrounding rock Zone VII. The model will consider the influence of the inhomogeneity of the mechanical parameters of the frozen surrounding rocks that are caused by the temperature field on the calculation results for the frost heave force. Based on the case analysis, the elastoplastic analytical solution of the stress and deformation of the surrounding rock in a cold region tunnel will be obtained. The results show that: (1) if the basic physical and mechanical parameters of the frozen surrounding rock are taken as constants, the calculation results of frost heave force, plastic radius (r_p), and circumferential stress (${\sigma }_{\theta }$) at the excavation radius will be smaller than that of the model proposed in this paper, and the freezing resistance design of the tunnel lining in cold regions based on the uniform parameter model might lead to lining damage due to insufficient support strength in the later stage; (2) the results of variance analysis show that the inner radius of the lining (r_a) and radius of Zone 7 (r₇) had a significant effect on the frost heave force in all cases, and the elastic modulus of the lining (E₀) was significant. The influence of the elastic modulus of Zone 7 (E₇) and in situ stress (p₀) on the frost heaving force was not significant; and (3) the influence law of the displacement release coefficient (η), E₀, and p₀ on the force that acted on the lining will be analyzed. The model to calculate the frost heave force and the related conclusions could have guiding significance for the frost resistance design and numerical simulation of tunnels in cold regions.

The objective of this paper is to investigate the behavior of strip shell footings subjected to axial and eccentric loads resting on a cylindrical steel rods assembly that simulates granular soil. An image processing analysis called particle image velocimetry (PIV) is used to obtain the displacement field around the footings. The bearing capacity and ultimate settlements of the footings are presented that show a linear variation with respect to the footing peak angle. The efficiency of eccentrically loaded shell footings is also discussed using settlement and rotation factors. Shell footings are proven to demonstrate better performance under eccentric loading in terms of settlement compared with axial loading cases, while a better performance is found at low eccentricities in terms of rotation. The PIV analysis provided the opportunity for a deeper comprehension of ground wedges beneath the footing and a comparison of results with analytical methods that validated the experimental results. Eventually, an eccentricity factor is proposed for the upper-bound solution to make it applicable for nonaxial loading cases.

Shear strength (τ) analysis has received considerable attention, because of its importance when designing various geotechnical structures, such as tunnels, retaining walls, shallow foundations, and slopes. Predicting the unsaturated τ from water retention curves (WRCs) is an existing method. The validity of this method for the prediction of unsaturated τ over a wide suction (ψ) range has been discussed by several researchers. However, the existing method ignores the influence of void ratio (e), which plays a strong part in the water holding capacity and the τ analysis of unsaturated soils. Therefore, according to an existing WRC equation that distinguishes capillary water and adsorbed water, a new WRC equation was proposed to consider the effect of e on the water holding capacity. In addition, using the e dependent WRC, a new method that predicted the τ of unsaturated silts or silty clays at various e over a wide ψ range (that included the residual zone) was proposed. The prediction of τ by the proposed method produced better predictions for experimental data than that of the existing method.

In this work, the influence of different types of fine materials on the shear-induced instability of sand–fines mixtures was studied from various aspects. For this purpose, clean sand was mixed with three kinds of fines with different plasticity indices (PIs)––silt (PI =15), clay (PI =21), and diatomaceous silt (PI =70). A new fines classification system was used that suggested that the high PI of diatomaceous silt is not due to electrochemical forces, but to the porous skeletons of diatoms producing high Atterberg limits. Multiple series of undrained triaxial tests were performed in order to evaluate the collapsibility potential of the mixtures. The equivalent intergranular void ratio, as a state variable, was used to evaluate the behavior of the mixtures. It was found that the equivalent intergranular void ratio can reduce the influence of fines and provide a strong correlation bearing several aspects of the mechanical behavior of coarse-grained–fines mixtures.

Seismic stability of geotechnical structures is an essential issue in earthquake geotechnical engineering. The pseudostatic method is the most common method for seismic stability analysis of geotechnical structures. The pseudodynamic method was developed, considering the phase differences and time effects; however, it does not satisfy the zero stress boundary conditions at the surface. A modified pseudodynamic method was proposed according to the zero stress boundary conditions for harmonic base motion. In the formulation of the modified pseudodynamic method, the ground motion of an earthquake with its frequency content is not considered. Also, the imaginary part of the response related to the damping effect is removed, making it more difficult to develop than expected. The pseudostatic and pseudodynamic methods are overestimated because the failure wedge is determined similar to the static method. This study aims to propose a new pseudodynamic method for seismic analysis of geotechnical structures considering the earthquake ground motion and both the real and the imaginary parts of the response. New transfer functions are introduced to obtain inertial forces and seismic active pressure based on the input motion. Furthermore, according to the experimental observations and momentum theory, a new method is proposed to determine the critical failure surface accurately. A comparison with a few experimental and analytical results in the literature is also presented. The results of the proposed method are in good agreement with the experimental and analytical results. Finally, an example is provided to illustrate the application of the proposed method. The effects of shear wave velocity and wall height on the seismic active pressure during an earthquake are investigated.

The quantification of the moistening deformation for wetting-sensitive unsaturated loess is of direct interest in regions implementing geotechnical engineering. Many constitutive models are available for describing the stress–strain behavior of unsaturated soils. However, few constitutive models directly describe moistening deformation. In this study, two types of triaxial tests were carried out on undisturbed loess. A triaxial compression test was conducted to determine the shear strength boundary of a specimen, and a triaxial moistening test with different stress ratios was used to study the moistening deformation law. The volumetric strain caused by moistening was used as the hardening parameter. A humidity variable was defined as the moisture level, and this parameter could reflect the moistening degree. The experimental rule and plastic theory were combined to establish the constitutive model. The model could directly calculate the deformation amount caused by moistening under different stress states. The model is applicable to the loess in the Guanzhong area in the Chinese Loess Plateau.

Fissures inside expansive soils play a crucial role in triggering the failure of a slope. However, few methods have been developed to model such irregularly inclined fissures in slope stability analysis. This study will propose a simple but efficient advanced approach to quantify the fissure structures that is based on the random field theory, in which the spatial heterogeneity of soil strength can be represented together. The stability analysis of expansive soil slopes that contain fissure surfaces (FSs) under various inclinations will be performed using the random finite-element method. For each scenario, the factors of safety (FoS) that are obtained by conducting Monte Carlo simulations (MCSs) will be statistically analyzed. The slope failure mechanism for several typical scenarios will be discussed in detail. The findings demonstrate that an expansive soil slope might become vulnerable when the slope angle is close to the inclination of FSs. The FoS that results from a uniform soil slope gives an overestimation of slope stability compared with that obtained from a slope model that contains FSs. In addition, the failure mode evolution of a fissured soil slope is strongly related to the fissure inclination, because the irregularly inclined FSs might directly form part of the potential sliding surface. Except for this effect, slope instability will probably develop along those local regions of weaker soil strength. These results could offer practical suggestions for the design or reinforcement of soil slopes with developed FSs, which could serve as sustainable smart and green life cycle solutions for geotechnical slope systems.

In this paper, the discrete element method (DEM) is coupled with the Lattice Boltzmann method (LBM) to model the cone penetration test (CPT) of a saturated granular media. The coupled numerical model was calibrated using one-dimensional (1D) consolidation theory. The results obtained from the 1D consolidation test simulation showed good agreement with the analytical equation that was proposed by Terzaghi. A series of LBM–DEM simulations were carried out to understand the effect of the penetration rate on the behavior of saturated granular materials during the CPT. The model has predicted a significant influence on the excess pore fluid pressure (Δu) and an insignificant influence on the cone resistance responses (q_t) and has qualitatively captured the effect of penetration rate, which was consistent with the experimental data. The simulation results showed that Δu increased with an increase in the penetration rate. The particle displacement and fluid velocity (U) contours have provided insights into the particle behavior and fluid pressure fluctuations during CPTs. The increase in Δu was attributed to the fluid pressure gradients that were created by the cone in the fluid system based on the penetration rate. The pore pressure distribution plots have shown a maximum pore fluid pressure below the cone region and over the cone shoulder position. A consistent evolution pattern of fabric anisotropy has been observed throughout the depth (z) under all the penetration rate conditions. The fabric components $({\mathrm{\varnothing }}_{22})$ and $({\mathrm{\varnothing }}_{11})$ have dominated around the cone area and at the boundary region, respectively. This indicates the preferential orientation of contacts in the vertical direction at the cone region and the horizontal direction at the boundary region. The simulation results have demonstrated that the LBM–DEM model can efficiently simulate the CPT and associated pore fluid pressure, which included the cone–particle–fluid interactions during CPTs.

The stability of rock engineering in cold regions is deteriorated by the day–night and seasonal freeze–thaw environments. Therefore, it is crucial to develop a damage constitutive model that can effectively describe the damage evolution and deformation characteristics of rock under freeze–thaw cycles. In this work, a series of laboratory tests were performed to acquire the physical and mechanical evolution characteristics of anhydrite rock subjected to freeze–thaw processes. Experimental results show that as the number of freeze–thaw cycles increases, the triaxial compression strength and elastic modulus of anhydrite rock decrease exponentially, but the mass variation, ductility deformation characteristics, and micropores’ area increase. A new statistical constitutive damage model for anhydrite rock under freeze–thaw cycles considering the residual strength and postpeak stress dropping rate was proposed based on the theory of continuous damage mechanics and Lemaitre’s strain-equivalent principle. The physical meaning of the model parameters m, f₀, and n represent the brittleness, ductility, and postpeak stress dropping rate of rock, respectively. Compared with the reference model, the proposed model can effectively reflect the postpeak stress dropping rate and the residual strength of the stress–strain behavior for rock with a minor error. Moreover, it is proved that the proposed model is applicable for other types of rocks with similar damage mechanisms.

The safety evaluation of three-dimensional rock or soil slopes strongly depends on the factor of safety based on the potential direction of sliding body. In fact, considering the objectivity of sliding, there should be a fixed main sliding direction for a potential landslide mass. However, in the past, there was no reasonable explanation for defining the main direction of sliding and it used to be considered as a variable to be optimized. In this paper, a refined finite-element limit-equilibrium method is proposed in couple with a fixed main direction of sliding to evaluate the safety of the three-dimensional slope. In this approach, the potential main direction of sliding can be directly determined as the projection direction of the resultant sliding force of the landslide on the horizontal plane once the stress field of sliding body was achieved. Theoretical derivations and several classical examples are performed for verification. The factor of safety of a sliding body in relation with the main direction of sliding are calculated and the results are comparable and consistent with the theoretical solutions. It is proven that the proposed slope stability analysis method based on the main direction of sliding could provide an alternative and convenient tool for engineering on design and reinforcement for rock or soil slope.

This paper proposes a progressive approach to assess the properties of large-scale roughness at dam–rock interfaces and the implementation of their effects into practical dam stability analyses. The analysis steps, ranked per increasing degree of complexity, consist of studying a gravity dam monolith using, first, the gravity method (GM), second, the finite element (FE) method (FEM) with a simplified horizontal planar dam–rock interface, and, third, the FEM with a detailed irregular geometry of the dam–rock interface. In the first two steps, the simplification of the rock foundation geometry is paired with the implementation of apparent cohesion and friction angle into the models. These apparent parameters are evaluated based on nonlinear shear strength criteria combined with an interface roughness coefficient (IRC) introduced to characterize the roughness of a dam–rock joint extending along the whole dam footprint. This coefficient is approximated herein numerically based on FE models. The inputs and steps of the progressive approach are illustrated through several examples of typical dam–rock systems and rock profiles based on bathymetric and LiDAR surveys. The results mainly show that the effects of rock foundation roughness on dam sliding stability can be efficiently represented with apparent cohesion and friction angles. The effectiveness of the simplified models coupled with the conservatism of the results they provide are likely to favor their adoption by practicing engineers.

The uncertainty rock mechanical parameters (i.e., deformation and strength parameters) is an important factor in the safety estimation and support design of underground engineering. Ignoring this uncertainty could allow potential risks to the structure. To address this challenge, this paper develops and verifies a Bayesian approach for a rock’s mechanical parameters estimation by integrating limited site data and prior knowledge, and the integrated knowledge is then transformed into a large number of equivalent samples of the rock’s parameters. The experimental data of marble from triaxial compression tests are first used to verify this method, and the results show that this method can effectively estimate the distribution of the marble’s deformation and strength parameters under the condition of small samples. Further, the probability distribution of rock mass parameters is obtained with the help of Hoek–Brown criterion. Then, the random field of the rock mass with a large cavern is constructed according to the obtained parameter distribution, the influence of different autocorrelation distances is discussed, and the excavation-induced deformation’s statistical analysis is carried out. Finally, the failure of the surrounding rock is characterized probabilistically, which can be a reference to the reliability design of rock support in underground engineering.

This paper presents a detailed investigation on quantifying the changes in the penetration resistance and undrained shear strength of clayey soil due to the installation of floating stone compaction columns. The columns were of 100-mm diameter, provided at 300-mm center-to-center spacing up to a depth of 5.0 m, and constructed using 6-mm broken stones. A total number of 12 locations were selected for the study considering various aspects. Standard Penetration Test and Static Cone Penetration Tests were conducted in the field and the penetration resistance of virgin soil and soil after stone column installation was investigated. The study was extended up to 2 years after installation to understand the behavior due to dissipation of pore water and consolidation settlement. A considerable increase in penetration resistance and hence an improvement in shear strength was observed due to the installation of floating stone compaction columns/piles (FSCPs). Empirical relations are proposed for predicting SPT N value after installation, and effective angle of internal friction for granular material and soil after installation.

Well integrity in composite well systems is an important safety issue in supercritical carbon sequestration. Although many studies have been devoted to evaluating the failure risks associated with composite well systems, time-varying cement properties have typically been ignored in numerical modeling despite a significant amount of experimental evidence demonstrating that material degradation occurs in CO₂-enriched environments. In this study, thermal–mechanical modeling with time-varying cement parameters is performed to evaluate the impact of cement degradation on stress distribution due to casing pressure and/or changes in temperature. A coupled thermal–mechanical problem was solved using the finite-element method. The model was verified by comparing the results to previous studies that did not consider material degradation. Then, the impact of cement degradation was explored. The results demonstrated that tensile hoop stress is sensitive to cement degradation due to a decrease in the elastic modulus and an increase in the Poisson’s ratio. There were also significant differences found in terms of radial stress when cement degradation was considered as compared to when it was not. Therefore, time-varying material properties should be considered when evaluating the integrity of cement sheaths in supercritical CO₂ sequestration environments.

The design of mechanically stabilized earth (MSE) walls depends greatly on the maximum tensile loads developed in the reinforcement layers. In practice, it has been found that the measured tensile loads significantly differ from the predicted values, and it is quantified by a bias value named load bias. It is defined as the ratio of the measured to the predicted maximum tensile load. Further, to evaluate the load bias, prediction of the maximum tensile load in reinforcements needs to be assessed properly for wall safety. Therefore, in this paper, a new artificial neural network (ANN)-based response surface method has been proposed to predict the maximum tensile load developed in reinforcements of MSE walls reinforced with steel strips. Both tensile strength and pullout limit states have been considered in this study. The sensitivity of the proposed load model on the design outcome (reliability index or probability of failure) has been assessed and compared with the existing response surface-based load model. One practical example problem has been considered, and the feasibility of the proposed model in predicting the reliability index (or probability of failure) is examined for different values of coefficient of variation of the nominal load and resistance. Design charts in terms of the failure probability of the wall over depth are presented throughout this study for both tensile strength and pullout limit states, and results reveal that the satisfactory performance of the proposed load model is achieved in predicting the reliability of the wall.

To better predict the response of laterally loaded caissons and the displacement distribution around the foundations, three different beam theories [Timoshenko beam theory with vertical (z) displacement in soil, Timoshenko beam theory without z displacement, and rigid beam theory with z displacement] were compared in the energy-based variationally method, and two caissons from real projects under the initial loading state were studied. The results from the three methods are compared with measured data from field tests and three-dimensional differential analysis. From the study, the method of the Timoshenko beam theory that considers z displacement in the soil domain produces the most accurate results. The rigid beam theory produced the worst prediction when estimating caisson displacement, rotation, and bending moment. Therefore, for the structure–soil interaction of a laterally loaded caisson, the suggested structure is a Timoshenko beam, and the vertical soil movement around the beam should be considered.

Low-permeability sandstone generally exists in oil and gas reservoirs. During oil and gas exploitation, reservoir pressure depletion causes significant plastic deformation and damage evolution. In reservoir history matching, it is vital to study the mechanical behaviors of sandstone considering both the coupled elastoplastic damage and permeability evolution. In this paper, a series of triaxial compression tests were performed to study the coupled elastoplastic damage mechanical behaviors of low-permeability sandstone. The permeability changes during the tests were obtained by using gas as a permeability-measuring medium. The results showed that due to the coupled effects of plastic deformation and damage evolution, the stress–strain presented obvious nonlinear and softening characteristics. A coupled elastoplastic damage model was first proposed to study the elastoplastic behaviors and damage evolution of low-permeability sandstone. Furthermore, a coupled elastoplastic damage mechanical model of low-permeability sandstone considering permeability evolution was put forward. The model can effectively describe the mechanical behaviors of low-permeability sandstone, which are in good agreement with the experimental results.

Within the framework of second-order cone programming optimized micropolar continuum finite-element method (CosFEM-SOCP), the geotechnical strain localization can be adequately modeled. In most existing literatures, however, the constant internal characteristic length l_c has been adopted and less attention has been paid to the evolution of l_c. To more accurately predict the strain localization, response, and stability of a geotechnical system, one relationship for evolving l_v that relies on the equivalent plastic strain is implemented and investigated. Based on one homogeneous slope example and one rigid strip footing example, it was found that geotechnical stability may not be significantly affected by evolving l_v, indicating that constant l_c can be simply applied to geotechnical stability analysis. For the rigid strip footing problem, nevertheless, the effects of evolving l_v on the pressure–displacement response curves should not be ignored, and the influence range of the shear band predicted by CosFEM-SOCP with evolving l_v is generally smaller than that predicted by CosFEM-SOCP with constant l_c. Consequently, in order to more accurately predict the pressure–displacement response curves and the failure zone, the evolving l_v will be adequately assessed and modeled.

Tunneling in soft clay requires accurate estimation of the inner support pressure to prevent undesired ground settlement and maintain the overall soil stability. Previous researchers have shown that the stability factor approach, which is analogous to Terzaghi’s bearing capacity factors [critical stability number (N_c), N_s, and N_γ)], is effective and efficient to determine the limit loads of many geotechnical stability problems. Therefore, this paper aims to study the stability factors of four various tunnel shapes in undrained clay: the two-dimensional (2D) tunnels of circular, square, and heading in plane strain, and the three-dimensional (3D) circular tunnel heading. Using the advanced finite-element limit analysis (FELA), rigorous upper-bound (UB) solutions of the undrained stability factors (F_c, F_s and F_γ) will be produced for various tunnel depth ratios (C/D). Numerical UB results are compared with lower bound (LB) solutions. Comprehensive design charts, tables, and equations will be presented for practitioners to estimate the critical tunnel support pressure at collapse.

In this study, limit equilibrium-based semianalytical solution has been developed to compute the distribution of active pressure and the magnitude and point of application of the total active thrust resulting from unsaturated backfills against inclined walls. Unlike earlier studies, the coupled effects of saturation-dependent suction stress and unit weight of the unsaturated soil mass above the water table has been considered to provide a realistic solution. Two separate analyses have been carried out to examine the potential impact of steady infiltration flow rates for the no-seismic case and for pseudostatic horizontal seismic forces for the no-flow case on the active pressure of unsaturated backfills. The results of the present analyses clearly reveal the potential effects of different parameters and tensile stress on the wall resulting from cohesion and suction stress components of unsaturated soil mass. It was noted that the nature of the variation of the active soil pressure distribution is highly dependent upon the hydraulic and mechanical properties of the unsaturated soils. This paper presents a simple, yet valuable, method for assessing the service state stability and performing forensic analyses of earth retention structures with unsaturated soil backfills.

Tests were conducted on bentonite–silica fume mixtures (BSFMs) to determine how particle size affects the volumetric shrinkage of bentonite–sand mixtures (BSMs) used as hydraulic barriers in waste disposal facilities. Free desiccation tests, liquid limit tests, plastic limit tests, and direct shear tests were conducted to compare the soil shrinkage characteristic curves, shrinkage limits, plasticity, and shear strength of BSFMs to that of the commonly used bentonite–standard sand mixtures (BSSMs) at 30% sand percentage. BSFMs exhibited higher air entry values (up to 55.9% higher), shrinkage limits (up to 14.6% higher), final void ratio (up to 43.6% higher), peak shear strength (up to 115% higher), and a smaller percentage of volumetric shrinkage (10.8%) than BSSMs due to the particle contact and constrained particle movement. The liquid and plastic limits of BSFMs, in contrast, were also higher (up to 99.2% and 27.1%) than that of BSSMs. Particle size plays a critical role in controlling the shrinkage limits of BSMs compared to clay fractions.

This paper will present stability analyses and charts to estimate the factor of safety (FS) for partially submerged undrained slopes with linearly increasing strength with depth and unlimited foundation depth. The problem has been tackled previously by ignoring the free standing water when the soil below and above the external water level, buoyant (γ′), and saturated unit weight (γ_sat), respectively, were assigned. This could then be combined with a simple unit weight averaging formula. In this paper, an analytical method that is based on optimization analyses will be proposed and charts will be presented that deliver an equivalent homogeneous unit weight as a function of slope angle (β), water depth (d_w), and γ_sat. This equivalent unit weight (γ_equiv) will then be assigned to the entire slope and used in conjunction with the stability charts Hunter and Schuster proposed in 1968. The analyses will use an optimization approach that assumes circular failure mechanisms, which will be validated using finite-element (FE) strength reduction. In almost all cases, the charts that are presented in this paper led to a lower and more conservative FS than those obtained that used the simple weighted average approach. Some cases where the charts might lead to unconservative solutions when compared with FE solutions will be identified and discussed.