Anisotropic soils exhibit complex mechanical behaviours under various loadsing conditions, e.g., reversible dilatancy, three-dimensional failure strength, fabric anisotropy, small-strain stiffness, cyclic mobility, making it difficult to comprehensively capture these characteristics within a single constitutive model. Failure to capture anisotropic soil behavious may result in poor predictions in geotechnical engineering. Hence, to provide a unified prediction for the mechanical responses of anisotropic sand and clay under both monotonic and cyclic loading conditions, a fabric-based anisotropic constitutive model, i.e., the CASM-CF, is developed within the framework of the standard Clay and Sand Model (CASM) in this paper. Effects of small-strain stiffness and anisotropic elasticity are incorporated into the stiffness matrix to capture the stiffness variation over a wide strain range and reversible dilation. The fabric tensor defined by particle orientation and its evolution law are integrated into the CASM-CF model through the Anisotropic Transformed Stress (ATS) method. The plastic modulus is modified by considering cyclic loading history and stress reverse to better predict the mechanical responses of soils when subjected to cyclic loadings. The newly proposed model is employed to predict the mechanical behaviours of clay and sand under various strain scales and stress paths, including monotonic, cyclic, proportional, and non-proportional loading conditions, in the literature. Conclusions can be drawn that the model performs satisfactorily under various stress paths, and it has the potential to be used in the analysis of practical geotechnical applications of wide range.

The subject of the current paper is the dynamic behaviour of anisotropic half-plane with surface relief containing a flexible or rigid foundation and two buried lined or unlined tunnels under time-harmonic waves radiated via embedded line source. The aim is to anticipate the influence of different model key factors such as (a) the soil topography; (b) the soil anisotropy; and (c) the soil-tunnels and soil-foundation-tunnels interaction. The computational tool is the direct boundary element method (BEM) based on the frequency-dependent fundamental solution for 2D general anisotropic solid derived by the Radon transform. The lined tunnels are implemented in the numerical model by the sub-structuring approach, which allows an efficient numerical processing of integrals along the interface boundaries. Numerical scheme verification and parametric studies are performed, and respective concluding remarks are summarized. The obtained results clearly illustrate the dynamic response sensitivity to the soil anisotropy, the soil topography and the complex soil-foundation-tunnels interaction.

An improved method tailored for anisotropic soft soils is presented, integrating theoretical models and field data to calculate the grouting quantity required for tunnel foundations. Given the complexities of soil interactions, particularly under variable geological conditions, this approach incorporates nonlinear behaviors and empirical field data to improve accuracy. Our findings reveal that integrating these theoretical frameworks significantly enhances the understanding of stress-strain behavior during grouting, enabling precise calculations of both axial and vertical expansion. Validation against numerical simulations demonstrates the model's reliability, highlighting the influence of soil types and grouting depths on expansion dynamics. This method not only helps mitigate risks in tunnel construction but also enhances foundation reinforcement strategies, driving progress in geotechnical engineering. It is particularly valuable for urban tunnel projects in complex geological conditions, where ensuring ground stability and safety is crucial.

Fabric anisotropy significantly influences the mechanical behavior of sandy soils, potentially resulting in diverse failure patterns during shield tunneling owing to insufficient support pressure. In this paper, a set of specimens with bedding angles (alpha\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\alpha$$\end{document}) and an isotropic specimen are well generated to simulate active failure at the tunnel face using DEM. The evolving failure of the soil in distinct alpha\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\alpha$$\end{document} are scrutinized, and ground settlement is further explored. Furthermore, microscopic information is juxtaposed to systematically elucidate the influence of alpha\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\alpha$$\end{document} on failure patterns at a microscopic level. Macroscopic findings reveal that, aside from specimens with alpha\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\alpha$$\end{document} = 0 degrees and 90 degrees, particle displacement experiences deflection as it extends toward the ground surface in other specimens. However, this deflection behavior is only noticeable under conditions of large deformation. Additionally, across all specimens, the maximum displacement of the ground surface is observed in those with alpha\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\alpha$$\end{document} = 90 degrees, while the minimum value is noted in specimens with alpha\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\alpha$$\end{document} = 45 degrees. Notably, considerable particle rotation occurs within the shear face. However, the deflection behavior has not been found in specimens with alpha\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\alpha$$\end{document} = 0 degrees and 90 degrees. Similarly, in specimens with these two specimens, there is no noteworthy deflection observed in the principal direction of contact normal.

PurposeThis study aims to use regression Least-Square Support Vector Machine (LS-SVM) as a probabilistic model to determine the factor of safety (FS) and probability of failure (PF) of anisotropic soil slopes.Design/methodology/approachThis research uses machine learning (ML) techniques to predict soil slope failure. Due to the lack of analytical solutions for measuring FS and PF, it is more convenient to use surrogate models like probabilistic modeling, which is suitable for performing repetitive calculations to compute the effect of uncertainty on the anisotropic soil slope stability. The study first uses the Limit Equilibrium Method (LEM) based on a probabilistic evaluation over the Latin Hypercube Sampling (LHS) technique for two anisotropic soil slope profiles to assess FS and PF. Then, using one of the supervised methods of ML named LS-SVM, the outcomes (FS and PF) were compared to evaluate the efficiency of the LS-SVM method in predicting the stability of such complex soil slope profiles.FindingsThis method increases the computational performance of low-probability analysis significantly. The compared results by FS-PF plots show that the proposed method is valuable for analyzing complex slopes under different probabilistic distributions. Accordingly, to obtain a precise estimate of slope stability, all layers must be included in the probabilistic modeling in the LS-SVM method.Originality/valueCombining LS-SVM and LEM offers a unique and innovative approach to address the anisotropic behavior of soil slope stability analysis. The initiative part of this paper is to evaluate the stability of an anisotropic soil slope based on one ML method, the Least-Square Support Vector Machine (LS-SVM). The soil slope is defined as complex because there are uncertainties in the slope profile characteristics transformed to LS-SVM. Consequently, several input parameters are effective in finding FS and PF as output parameters.

The aim of this paper is to propose a two-stage theory-based analytical method for the dynamic performance of pile groups in layered poroelastic saturated cross-anisotropic soils induced by moving loadings. Among them, the free-field vibrational analysis of saturated soils is performed by the analytical element-layer approach (ALEA) and Fourier transformation. Based on the free-field response, the boundary element (BE) solution for the soil resistance at the soil-pile interface is derived utilizing the two-stage theory. Simultaneously, the finite element (FE) solutions for the pile shaft resistance and deformation of pile groups are derived based on the Timoshenko beam theory. Finally, the FE-BE coupled dynamic equation for deformations and internal loadings of the soil-pile system is obtained. Thereafter, the reliability of the proposed method is validated by comparing with existing solutions and FE data from ABAQUS. Based on the derived solutions, a comprehensive parametric study is performed to examine the effects of loading amplitude, force speed, soft soil-layer stiffness, soil anisotropy, and pile length on the dynamic responses of pile groups.

The current paper investigates wave propagation from time-harmonic embedded point source in a semi-infinite anisotropic medium containing underground structure by applying three different computational techniques. Firstly, direct BEM for 2D elastodynamics is applied using the fundamental solution derived by the Radon transform for general anisotropic continua. The second numerical technique is a computationally efficient two-and-a-half dimensional FEM, used to calculate the 3D wave field in the soil. At the boundaries of the mesh perfectly matched layers are instated to prevent spurious wave reflections. The FEM solutions realized by the built-in options in ANSYS are finally utilized with two types of absorbing boundary conditions. The results obtained by the three adopted modelling techniques are properly compared and respective insights regarding their applications are provided.