Bedrock-soil layer slopes (BSLSs) are widely distributed in nature. The existence of the interface between bedrock and soil layer (IBSL) affects the failure modes of the BSLSs, and the seismic action makes the failure modes more complex. In order to accurately evaluate the safety and its corresponding main failure modes of BSLSs under seismic action, a system reliability method combined with the upper bound limit analysis method and Monte Carlo simulation (MCS) is proposed. Four types of failure modes and their corresponding factors of safety (Fs) were calculated by MATLAB program coding and validated with case in existing literature. The results show that overburden layer soil's strength, the IBSL's strength and geometric characteristic, and seismic action have significant effects on BSLSs' system reliability, failure modes and failure ranges. In addition, as the cohesion of the inclination angle of the IBSL and the horizontal seismic action increase, the failure range of the BSLS gradually approaches the IBSL, which means that the damage range becomes larger. However, with the increase of overburden layer soil's friction angle, IBSL's depth and strength, and vertical seismic actions, the failure range gradually approaches the surface of the BSLS, which means that the failure range becomes smaller.

Earthquakes contribute to the failure of anti-dip bedding rock slopes (ABRSs) in seismically active regions. The pseudo-static method is commonly employed to assess the ABRSs stability. However, simplifying seismic effects as static loads often underestimates rock slope stability. The development of a practical stability analysis approach for ABRSs, particularly in slope engineering design, is imperative. This study proposes a stability evaluation model for ABRSs, incorporating the viscoelastic properties of rock, to quantitatively assess the safety factor and failure surface under seismic conditions. The mathematical description of the pseudo-dynamic method, derived in this study, accounts for the viscoelastic properties of ABRSs and integrates the Hoek-Brown failure criterion with the Kelvin-Voigt stress-strain relationship of rocks. Furthermore, to address concurrent translation-rotation failure in ABRSs, upper bound limit analysis is utilized to quantify the safety factor. Through a comparison with existing literature, the proposed method considers the effect of harmonic vibration on the stability of ABRSs. The obtained safety factor is lower than that of the quasi-static method, with the resulting percentage change exceeding 5%. The critical failure surface demonstrates superior positional accuracy compared to the Aydan and Adhikary basal planes, with minimal error observed between the physical model test and the numerical simulation test. The parameter sensitivity analysis reveals that the inclination of ABRSs exhibits the highest sensitivity (Sk) value across the three levels of horizontal seismic coefficient (kh). The study aims to devise an expeditious calculation approach for assessing the stability of ABRSs during seismic events, intending to offer theoretical guidance for their stability analysis. (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/).

Slope stability analysis in 2D ranges from the classical and conventional limit equilibrium method to the robust and computationally demanding finite element (FE) analysis. Discontinuity layout optimisation (DLO) is an interesting intermediate method that applies an upper bound limit analysis with the assumption of rigid-perfectly plastic soil behaviour. Here, the whole soil mass is discretized using a set of potential slip-lines and optimisation is used to identify the critical mechanism that can be formed from a subset of these lines that dissipates the least energy. This method has only been used for isotropic soil models, except for rare studies that included an anisotropic model. This paper introduces the use of an anisotropic failure criterion in DLO, based on the total stress-based NGI-ADP model. The performance of DLO with this simplified NGI-ADP model is compared with respect to failure mechanism and safety factor determined by corresponding FE analysis. The results show good agreement between the two methods and highlight the use of DLO as a powerful method with straightforward input parameters and low computational time for slope stability assessment.

The focus of the study is to examine the undrained behavior of twin circular tunnels in anisotropic and nonhomogeneous clays. To consider the effect of anisotropic soil, the popular anisotropic undrained shear (AUS) failure criteria are adopted in the study while the nonhomogeneous behavior is represented by linearly increasing strength with depth. Using Broms and Bennermarks' stability number, this study investigates the dependence of the undrained stability number N on four dimensionless input parameters, namely the isotropic ratio (re), the undrained shear strength gradient (rho D/suTC0), the cover depth ratio (C/D), and the spacing ratio (S/D). The effects of these four design parameters on the failure mechanism are also examined graphically. After being verified with previously published works, the comprehensive 1080 numerical results are then utilized as the dataset to create several machine learning models, including artificial neural network (ANN), support vector machine (SVM), and multivariate adaptive regression splines (MARS). The evaluating process by optimizing hyper-parameters reveals that the MARS model is a top competitor, providing considerable regression accuracy with a simple predictive function. The sensitivity analysis has also uncovered that both rho D/suTC0 and C/D have significant influences on the undrained stability number N, while comparing to re and S/D. The present study would provide many practical insights to the problem of twin circular tunnels in anisotropic and nonhomogeneous clays.

This study investigated active and passive lateral earth pressure in the presence of anisotropic seepage conditions. The soil was assumed to be granular and fully saturated. Three methods were used to solve the problem: (1) the upper bound limit analysis method (UBM); (2) upper and lower bound solutions of finite-element limit analysis (FELA); and (3) the stress characteristic method (SCM). The proposed analytical solution for the UBM employed the logarithmic spiral slip surface. The lateral earth pressure coefficients for the active and passive cases were calculated and presented, considering variations in the vertical-to-horizontal hydraulic conductivity ratio, friction angle, and soil-wall interface friction angle. The obtained results for the active and passive cases agree with those of previous studies. The results of the SCM showed that in the presence of seepage, the distribution of stress on the soil-wall interface is nonlinear. In addition, the failure zone obtained from different methods was compared and examined. The failure patterns obtained from the SCM and FELA were almost identical.

Conducting soil stability assessments around tunnels has always been a concern. However, most existing studies have regarded soil as an isotropic and homogeneous material. To overcome this limitation, within the framework of upper bound theory, this paper proposes a novel rotational-translational failure mechanism where the velocity discontinuity surfaces are derived numerically. This theoretical mechanism includes two cases according to the positions of the velocity discontinuity surfaces. An analytical solution for pore water pressure is obtained using the conformal mapping method, which involves solving the two-dimensional (2D) Laplace equation and considering the soil and shotcrete permeability. Then, upper bound expressions for the limit supporting pressure are derived by computing work equations with and without pore water pressure. Comparisons with previous work and numerical results illustrate that the presented approach offers improvements and could be applicable for stability analyses of shallow rectangular tunnels in anisotropic and nonhomogeneous soils. Finally, this paper discusses the effects of the anisotropy and nonhomogeneity of soil properties on the normalized limit supporting pressure and the collapsing domains of rectangular tunnels with different geometric shapes. In addition, the impact of pore water pressure on the changed water levels is assessed. The results demonstrate that for rectangular tunnels that are excavated in water-bearing zones, the width-to-height ratio plays a significant role in the stability of the surrounding soils.

Vegetation plays an important role in improving slope stability. It is crucial to develop simple and effective methods for assessing the stability of vegetated slopes. Based on upper bound limit analysis, a method was proposed to analyse the stability of a two-dimensional vegetated slope with uniform root architectures under steady transpiration state. The effects of water absorption and reinforcement by vegetation roots on slope stability were considered using this method. Parametric studies were performed to investigate the effects of the soil type, root depth, plant transpiration rate, root tensile strength, slope angle and internal friction angle on slope stability. Several generic stability plots were provided. The results showed that roots significantly improved soil cohesion but slightly affected the internal friction angle. Root systems could provide additional soil cohesion. Horizontally and vertically distributed roots imposed the best mechanical reinforcement effect on the soil. The shear strength increases by 1.78 times. Compared with that of plain soils, the critical state line (CSL) of the root-soil composite moved upwards. The soil type strongly influences the pore water pressure. With increasing plant transpiration rate, root tensile strength and root depth, vegetated slope stability can increase by 58 %. The slope stability decreases by 50 % with increasing slope angle. The stability number (Ns) decreases with increasing internal friction angle. The effects of water absorption and reinforcement by roots on slope stability decrease with increasing desaturation coefficient and saturated permeability coefficient. Compared with that of loess and sand slopes, the reinforcement effect of vegetation roots is more significant for the stability of clay slopes.

Assessing possible permafrost degradation related to engineering projects, climate change and land use change is of critical importance for protecting the environment and in developing sustainable designs for vital infrastructure in cold regions. A major challenge in modelling the future degradation of permafrost is finding ways to constrain changes in the upper thermal boundary condition over time and space at appropriate scales. Here, we report on an approach designed to predict time series of air, ground surface and shallow ground temperatures at a spatial scale on the order of 102?m2 for engineering design of a railway or highway project. The approach uses a regional-scale atmospheric model to downscale global climate model output, and then stepwise multiple regression to develop an equation that provides a best-fit prediction of site-specific observational data using bilinearly interpolated output from the atmospheric model. This approach bridges the scale difference between atmospheric climate models and permafrost thermal models, and allows for a wider range of factors to be used in predicting the thermal boundary condition. For a research site located in Beiluhe, China, close to the Qinghai-Tibet Railway, a comparison of model predictions with observational data not used in the construction of the model shows that this method can be used with a high degree of accuracy to determine the upper boundary condition for a permafrost thermal model. Once a model is constructed, it can be used to predict future changes in boundary condition parameters under different greenhouse emission scenarios for climate change. Copyright (c) 2012 John Wiley & Sons, Ltd.