The foundation soil below the structure usually bears the combined action of initial static and cyclic shear loading. This experimental investigation focused on the cyclic properties of saturated soft clay in the initial static shear stress state. A range of constant volume cyclic simple shear tests were performed on Shanghai soft clay at different initial static shear stress ratios (SSR) and cyclic shear stress ratios (CSR). The cyclic behavior of soft clay with SSR was compared with that without SSR. An empirical model for predicting cyclic strength of soft clay under various SSR and CSR combinations was proposed and validated. Research results indicated that an increase of shear loading level, including SSR and CSR, results in a larger magnitude of shear strain. The response of pore water pressure is simultaneously dominated by the amplitude and the duration of shear loading. The maximum pore water pressure induced by smaller loading over a long duration may be greater than that under larger loading over a short duration. The initial static shear stress does not necessarily have a negative impact on cyclic strength. At least, compared to cases without SSR, the low-level SSR can improve the deformation resistance of soft clay under the cyclic loading. For the higher SSR level, the cyclic strength decreases with the increase of SSR.

The structural characteristics of soil-rock mixture (SRM) slopes, including the content, shape, size, and spatial distribution of rock blocks, can significantly influence their failure mechanisms and factor of safety (FOS). Defining the structural characteristics of SRM slopes for stability analysis remains challenging. This study proposes a method for establishing random models and evaluating the statistical properties of the FOS values of SRM slopes. Accordingly, the SRM slope models were constructed by considering the random properties of the shape, size, and spatial distribution of rock blocks in the slope domain. A slope failure criterion based on energy changes and the combined subroutines of USDFLD and URDFIL was implemented in the ABAQUS finite element software to determine the FOS values of the SRM slopes. Monte Carlo simulations were performed to assess the statistical properties of the FOS for random SRM slopes varying rock block properties. The results indicated that when the rock block content was greater than 30%, the stability of SRM slopes considerably increased. For a rock block content of 40%, the effect of rock block size on the SRM slope stability followed two different trends: the mean FOS value tended to decline and subsequently increased as rock block size increased. However, this trend was not observed on SRM slopes with a 30% rock block content. Besides, the dispersion of the FOS values gradually increased with increasing rock content and rock block size. Furthermore, the soil-rock interface strength affected the stability and failure mechanism of SRM slopes. These findings enhance comprehension of the SRM slope stability assessment and demonstrate improved accuracy in predicting and mitigating damage.

A series of true triaxial unloading tests are conducted on sandstone specimens with a single structural plane to investigate their mechanical behaviors and failure characteristics under different in situ stress states. The experimental results indicate that the dip angle of structural plane (B) and the intermediate principal stress (o2) have an important influence on the peak strength, cracking mode, and rockburst severity. The peak strength exhibits a first increase and then decrease as a function of o2 for a constant B. However, when o2 is constant, the maximum peak strength is obtained at B of 90 degrees, and the minimum peak strength is obtained at B of 30 degrees or 45 degrees. For the case of an inclined structural plane, the crack type at the tips of structural plane transforms from a mix of wing and anti-wing cracks to wing cracks with an increase in o2, while the crack type around the tips of structural plane is always anti-wing cracks for the vertical structural plane, accompanied by a series of tensile cracks besides. The specimens with structural plane do not undergo slabbing failure regardless of B, and always exhibit composite tensile-shear failure whatever the o2 value is. With an increase in o2 and B, the intensity of the rockburst is consistent with the tendency of the peak strength. By analyzing the relationship between the cohesion (c), internal friction angle (4), and B in sandstone specimens, we incorporate B into the true triaxial unloading strength criterion, and propose a modified linear Mogi-Coulomb criterion. Moreover, the crack propagation mechanism at the tips of structural plane, and closure degree of the structural plane under true triaxial unloading conditions are also discussed and summarized. This study provides theoretical guidance for stability assessment of surrounding rocks containing geological structures in deep complex stress environments. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

We present an assumed enhanced strain finite element framework for the simulation of tensile fracturing processes in transversely isotropic rocks. Fractures along the weak bedding planes and through the anisotropic rock matrix are treated with distinct enrichment, and a recently proposed dualmechanism tensile failure criterion for transversely isotropic rocks is adopted to determine crack initiation for the two failure modes. The cohesive crack model is adopted to characterize the response of embedded cracks. As for the numerical implementation of the proposed framework, both algorithms for the update of local history variables at Gauss points and of the global finite element system are derived. Four boundary-value problem simulations are carried out with the proposed framework, including uniaxial tension tests of Argillite, pre-notched square loaded in tension, three-point bending tests on Longmaxi shale, and simulations of tensile cracks induced by a strip load around a tunnel in transversely isotropic rocks. Simulation results reveal that the proposed framework can properly capture the tensile strength anisotropy and the anisotropic evolution of tensile cracks in transversely isotropic rocks. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Energy dissipation can macroscopically synthesize the evolutions in the microstructure of the marine clay during cyclic loading. Hence an energy-based method was employed to investigate the failure criterion and cyclic resistance of marine clay. A series of constant-volume cyclic direct simple shear tests was conducted on undisturbed saturated marine clay from the Yangtze Estuary considering the effects of the plasticity index (IP) and cyclic stress ratio (CSR). The results indicated that a threshold CSR (CSRth) exhibiting a power function relationship with IP exists in marine clay, which divides the cyclic response into non-failure and failure states. For failed specimens, the development of energy dissipation per cycle (Wi) with the number of cycles (N) exhibited an inflection point owing to the onset of serious damage to the soil structure. In this regard, the energy-based failure criterion was proposed by considering the inflection point as the failure point. Consequently, a model was proposed to quantify the relationships between failure energy dissipation per cycle (Wf) [or failure accumulative energy dissipation (Waf)], initial vertical effective stress, IP, and the number of cycles to failure (Nf,E). An evaluation model capturing the correlation among CSR, IP, and Nf,E was then established to predict the cyclic resistance, and its applicability was verified. Compared with the strain-based cyclic failure criterion, the energybased failure criterion provides a more robust and rational approach. Finally, a failure double-amplitude shear strain (gamma DA,f) evaluation method applicable to marine clay in different seas was presented for use in practical geotechnical engineering.

In order to consider the effect of fabric anisotropy in the analysis of geotechnical boundary value problems, this study proposes a modified model based on a fabric-based modified Cam-clay model, which can account for the anisotropic response of soil. The major modification of the original model aims to simplify the equations for numerical implementation by replacing the SMP strength criterion with the Lade's strength criterion. This model comprehensively considers the inherent anisotropy, induced anisotropy, and three-dimensional strength characteristics of soil. The model is first numerically implemented using the elastic trial-plastic correction method, and then it is encapsulated into the FLAC(3D )6.0 software, and tested through conventional triaxial, embankment loading, and tunnel excavation experiments. Numerical simulation results indicate that considering anisotropy and three-dimensional strength in geotechnical engineering analysis is necessary. By accounting for the interaction between microstructure and macroscopic anisotropy, the model can more accurately represent soil behavior, providing significant advantages for geotechnical analysis.

The rock-based sea area has great prospect of development and construction of offshore wind farms (OWFs), and the mainstream construction sites of OWFs in China have shifted from the soil-based seabed to the rock-based seabed area. Previous studies about mechanical properties of seabed materials and bearing characteristics of pile foundation in OWF mainly focus on the submarine soil-based seabed, resulting in lack of direct reference for the construction of offshore wind power in the rock seabed. Therefore, the study concentrates on the investigation of failure criterion of submarine completely weathered granite (CWG) of offshore wind farms in rockbased sea area under cyclic loads. Firstly, dynamic triaxial tests are carried out, and two unique development modes of CWG are revealed under different cyclic loads. The experiments analyze insight stiffness attenuation law and establish the prediction model of stiffness attenuation based on the logarithm formula. More critical, a unique development law of damping ratio of submarine seabed materials is discovered and discussed, and two cyclic failure criteria based on cumulative strain and dissipated energy are put forward to divide the critical CSR under cyclic loads, which gives helpful reference for the construction of offshore wind farms in rock-based sea area.

This work introduces a theoretical framework for determining the active non-limit earth pressure of cohesive soil on a base-rotating rigid wall. The framework incorporates the nonlinear Mohr-Coulomb failure criterion, the Duncan-Chang hyperbolic stress-strain relationship, the log-spiral potential failure surface in retained soil, and a horizontal slice method for the earth pressure evaluation. The proposed method allows quantitative determination of displacement-dependent earth pressure and its distribution along the wall back. Practical wall movement in the at-rest state is considered, and the tension crack depth near the soil surface is calculated based on the soil tensile strength cut-off. Analysis results highlight the nonlinear variation of the mobilized soil shear strength vertically, influenced by the nonlinear Mohr-Coulomb failure criterion. As the wall rotation increases, the earth pressure follows a convex parabolic distribution with a tension failure zone near the soil surface and no pressure at the wall base. The resultant of the earth pressure reduces and its application point descends while the tension crack depth expands, though always remaining less than the Rankine's earth pressure. A practical example shows that the at-rest earth pressure can be up to 1.3 times greater than the active earth pressure, with the resultant application point approximately 5% higher. Parameter study exhibits that the active non-limit earth pressure correlates nonlinearly with the soil ultimate tensile stress and nonlinear coefficient, particularly as wall movement increases. Active non-limit earth pressures vary within 86% across different soil cohesions, and up to 50% under varying ultimate tensile stresses and nonlinear coefficients. Overturning safety factors of the wall in the active non-limit state differ significantly from those in the at-rest state, especially under varying soil cohesions.

Among various available methods for slope analysis, the limit equilibrium method is very popular because of its simple concepts. The limit analysis method and the finite element method (FEM) also can perform stability analysis of a slope. Increasing computing power and the easy accessibility of inexpensive numerical modeling codes have made the finite element method a very attractive tool for the practical assessment of slope stability. The present study reports the results of slope stability analysis of a few problems analyzed using a developed program utilizing FEM. This program employs a strength reduction technique based on FEM. Mohr-Coulomb strength criterion of soil is used for predicting the stress state, while the viscoplastic algorithm is used for stress redistribution. Non-convergence of the algorithm to achieve the desired equilibrium of all forces in the system is adopted as a marker of slope failure. Further, to put the proposed method to the test, a few examples from the literature are analyzed using the developed program. The example problems cover a homogenous slope with water loading, an inclined layered slope, and a staged embankment subjected to different forms of loading including earthquake forces, pore water pressure, external water pressure, etc. The results of each analysis are compared with other researchers work, and it is found that the obtained results are in good agreement. Deformed mesh, equivalent viscoplastic strain contour plots, and failure function contour plots are used for illustrating the failure state.

To understand the strengths of rocks under complex stress states, a generalized nonlinear three-dimensional (3D) Hoek-Brown failure (NGHB) criterion was proposed in this study. This criterion shares the same parameters with the generalized HB (GHB) criterion and inherits the parameter advantages of GHB. Two new parameters, b, and n, were introduced into the NGHB criterion that primarily controls the deviatoric plane shape of the NGHB criterion under triaxial tension and compression, respectively. The NGHB criterion can consider the influence of intermediate principal stress (IPS), where the deviatoric plane shape satisfies the smoothness requirements, while the HB criterion not. This criterion can degenerate into the two modified 3D HB criteria, the Priest criterion under triaxial compression condition and the HB criterion under triaxial compression and tension condition. This criterion was verified using true triaxial test data for different parameters, six types of rocks, and two kinds of in situ rock masses. For comparison, three existing 3D HB criteria were selected for performance comparison research. The result showed that the NGHB criterion gave better prediction performance than other criteria. The prediction errors of the strength of six types of rocks and two kinds of in situ rock masses were in the range of 2.0724%-3.5091% and 1.0144%-3.2321%, respectively. The proposed criterion lays a preliminary theoretical foundation for prediction of engineering rock mass strength under complex in situ stress conditions. (c) 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V.