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.

This paper analyzed the influence of the inherent anisotropy of sand on active and passive arching by simulating the trapdoor emplying the discrete element method (DEM). The inherent anisotropy is reflected by the bedding plane angle alpha of particles. The granular material constitutive responses are captured on representative volume elements (RVEs). A new modeling method is employed to prepare particle specimens, aiming to obtain a more uniform soil model. The results indicate that the discrete element method can simulate the influence of the inherent anisotropy of granular material on the evolution of soil arching. An asymmetric arching evolution phenomena is observed in the alpha other than 0 degrees or 90 degrees cases, which leads to obvious asymmetric deformation and stress distribution in the soil. As the filling height increases, this phenomenon becomes more and more obvious. From a microscopic perspective, the reorientation of the contact normal fabric caused by particle rotation is the main reason for the differences in soil arching evolution with different alpha. This study provides a theoretical basis for predicting ground deformation failure caused by underground engineering activities and changes in surrounding environmental conditions.

This study examines the behavior of anisotropically consolidated granular assemblies under undrained cyclic true triaxial loading paths. To achieve this, the Discrete Element Method (DEM) is conjugated with the Coupled Fluid Method (CFM) to account for fluid-solid interaction in undrained conditions. The examined loading paths include two phases: anisotropic consolidation and undrained cyclic true triaxial loading. During consolidation, samples are sheared at various Lode angles to reach a spectrum of initial static shear stress levels. In the second stage, undrained cyclic loading is applied with constant shear stress amplitudes at various Lode angle values. The results indicated that the monotonic and cyclic Lode angle, initial static shear stress, and amplitude of deviatoric stress have pronounced effects on the secant shear modulus degradation and the rate of excess pore water pressure generation of granular assemblies. In tandem with macro-scale observations, the evolution of the microstructure within assemblies is analyzed using the coordination number, redundancy index, inter-particle contact fabric tensor, and particle orientation fabric tensor. The micro-scale findings confirm that the anisotropy induced by changes in the loading direction significantly impacts the shear strength of the assemblies. Additionally, the fabric of assemblies aligns along the preferential direction corresponding to the major principal stress, influencing the dilative response.

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.

The aim of this study is to reveal the influence of frozen soil anisotropy and thermal-hydraulic-mechanical coupling effects on the frost heave deformation behavior of sheet pile walls (SPWS) through numerical simulation and experimental verification. In this research, a thermal-hydraulic-mechanical (THM) model of frozen soils is improved by integrating the anisotropic frost deformation firstly. Then, considering the shear characteristics of soil-structure interface, a finite element analysis of SPWS during freezing is conducted based on the proposed THM model. The simulation results are then validated by a small-scale simulation test. The results shown that, the pile is subjected to large bending moments and normal stress at the junction between the embedded and the cantilever section. Embedment depth of pile is suggested to set be 1/3 to 1 time the overall lenth, which having a greater effect on antiing the frost deformation. Numerical simulation considering the anisotropic of frozen soil is closer to the experimental results than traditional calculation methods. The THM numerical method can well characterize the directional relationship between temperature gradient and pile deformation. In seasonal frozen soil areas, deformation numerical simulation that can be further developed by considering the effects of multiple freeze-thaw cycles in subsequent research.

Accurate determination of potassium ion (K+) concentration in fingertip blood, soil pore water, pipette solution, and sweat is crucial for performing biological analysis, evaluating soil nutrients levels, ensuring experimental precision, and monitoring electrolyte balance. However, current electrochemical K+ sensors often require large sample volumes and oversized reference electrodes, which limits their applicability for the aforementioned small-volume samples. In this paper, a K+ sensor integrated with a glass capillary and a spiral reference electrode was proposed for detecting K+ concentrations in small-volume samples. A K+-selective membrane (K+-ISM)/ reduced graphene oxide-coated acupuncture needle (working electrode) was spirally wrapped with a chitosangraphene/AgCl-modified Ag wire (reference electrode). This assembly was then inserted into a glass capillary, forming an anisotropic diffusion region of an annular cylindrical gap with width 410 mu m and height 20 mm. It was found that the capillary action of the glass capillary results in a raised liquid level of the sample inside it compared to that in the container, which promotes efficient contact between the small-volume sample and the K+ sensor. Besides, the formed anisotropic diffusion region limits the K+ diffusion from the bulk solution to the K+ISM, which leads to a larger potentiometric response of the K+-ISM. The glass capillary-assembled K+ sensor displays high performance, including a sensitivity 58.3 mV/dec, a linear range 10_ 5-10_ 1 M, and a detection limit 1.26 x 10_6 M. Moreover, it reliably determines K+ concentrations in artificial sweat of microliter volume. These results facilitate accurate detection of K+ concentration in fingertip blood, soil pore water, and pipette solution.

Soft clay is the primary soil type encountered in engineering construction in the eastern coastal regions of China. The deformation characteristics of soft clay are closely related to its inherent stiffness. Under the action of long-term geostatic stress and external load, the dynamic behavior and characteristics of soil in vertical and horizontal directions are different, i.e., anisotropy. In this study, the dynamic parameters of saturated soft clay samples were investigated through bidirectional dynamic step-amplitude cyclic triaxial experiments. The anisotropic stiffness evolution of soft clay over a wide strain range was analyzed, and the effects of different consolidation states on the development of dynamic shear modulus and damping ratio were also examined. Under the same confining pressure, the soft clay samples subjected to axial step-amplitude cyclic loading exhibited higher ultimate dynamic stress values in backbone curves compared to those under radial step-amplitude cyclic loading, while the obtained shear modulus showed the opposite trend. The anisotropic stiffness ratio of soft clay samples tended to increase with increasing confining pressure, with an average value of 1.25 in the range of 100-300 kPa. The shear modulus of the samples increased with increasing confining pressure and consolidation stress ratio but decreased with increasing overconsolidation ratio (OCR).

This study provides a comprehensive analysis of the undrained failure envelope for spudcan foundations in anisotropic clays using the AUS failure criterion as the soil strength model. The influence of embedment depth (L/D) and anisotropic strength (re) on spudcan behaviour under combined loading conditions is investigated. Failure envelopes are derived through three-dimensional finite element limit analysis (3D FELA) in both (H/ suTCA, M/suTCAD) and (V/Vult, H/suTCA, M/suTCAD) spaces. The study also illustrates spudcan foundation failure mechanisms, providing valuable insights for designing footings in anisotropic clays under combined loads (V, H, M). Additionally, an innovative soft-computing approach is introduced: a machine learning model that integrates categorical boosting (CatBoost) with the flower pollination algorithm (FPA) for optimized predictions of the spudcan failure envelope. The proposed FPA-CatBoost model is validated against numerical FELA results, demonstrating a strong correlation and offering engineers a reliable tool for determining spudcan foundation failure envelopes under varied loading conditions.

Waterfront and submarine retaining structures are normally exposed to catastrophic seepage conditions under the effect of tidal and occasionally heavy rainfall effect, resulting in a decreased passive earth thrust and thus the higher risk of instability of retaining structures. To examine the effect of seepage flow on the magnitude and distribution of passive earth thrust, this paper assumes a composite curved-planar failure surface and presents a modified method of passive earth pressure considering the seepage flow effect. The flow field and pore pressure are firstly solved by the two-dimensional (2D) Laplace equation using the Fourier series expansion. The effective reaction force acting on the composite failure surface is then obtained using a modified K & ouml;tter equation. Compared to conventional methods based on limit equilibrium, the present method facilitates a straightforward assessment of both the magnitude and distribution of passive earth thrust without the prior assumption of the application point. The outcomes highlight that the passive earth thrust decreases with the ratios of permeability coefficients. The greater effective friction angle and a smaller ratio of permeability coefficients result in the lower application point of the passive earth thrust.

The study presents a comprehensive study on the assessment of the bearing capacity of closely spaced strip footings on c-& oslash; soil, considering spatial variability in soil properties. A linear elastic model is employed for footings and elastic-perfect plastic soil behaviour via the Mohr-Coulomb yield criterion. Soil properties obtained from extensive field investigations of Taranto Blue Clay (TBC) in Italy are modelled as stationary random fields (RFs) generated using the Fourier series method. The cohesion and friction angle RFs are integrated with the Z-soil FE code. The final results are obtained according to the random finite element method (RFEM). The study investigates the influence of spacing distances between footings and spatial correlation lengths of soil parameters on the bearing capacity. Results show how spacing distance affects bearing capacity. Moreover, it indicates that neighbouring footing bearing capacity is strongly correlated with investigated parameters. In the case of small spatial correlation lengths, the patterns were obtained as non-symmetrical, transitioning to more symmetrical patterns at larger lengths. The manuscript concludes by presenting reliability-based design considerations for the ultimate bearing capacity, considering the horizontal spatial scale of fluctuation (SOF). The findings emphasize the importance of evaluating allowable design bearing capacity for proximity structures using RFEM and provide valuable insights into the interplay between spacing distances and spatial variability in soil properties. To this end, the study underscores the critical interplay between spacing distance, spatial correlation lengths, and random soil properties in assessing neighbouring footing-bearing capacities.