As a new type of granular backfill material, calcareous sand is widely used in the construction of marine transportation infrastructure. And they are subjected to complex irregular long-term dynamic loading such as that from waves, traffic and even earthquakes. In this paper, 22 groups of undrained cyclic shear tests were performed with calcareous sand under various cyclic stress ratios and cyclic stress paths. The influence mechanism of stress path on the cyclic shear behavior of calcareous sand was investigated. The results show that the ultimate residual pore pressure at critical state was not affected by cyclic stress ratios and paths. But the cyclic shear behaviors of calcareous sand including failure pore water pressure and long-term deformation were changed significantly. Axial load plays a dominant role in each stress path. A stress path parameter omega was proposed to characterize the vertical shaking impact of cyclic stress paths with different initial orientation of the sigma 1 axis to vertical alpha sigma 0. And a power function of omega was used to describe the involvement level of soil skeleton in anti-liquefaction. This parameter performs well in representing cyclic stress paths with different orientation to the vertical. A series of formulas were proposed to predict the failure residual pore pressure and the long-term cumulative deformation behavior of calcareous sand. More accurate shakedown discriminant boundaries suitable for almost unbroken calcareous sand were proposed.

Microbially induced calcite precipitation (MICP) is a promising technology for soil improvement, where the treated soil can be regarded as the structural one. In this study, a micromechanics-based model is proposed to investigate the mechanical behaviors of inherently anisotropic MICP-cemented sand, which consists of a hexagonal close-packed (HCP) particle assembly (2D) composed of bonded elliptical particles with same size. A size-dependent bond failure criterion is adopted to define the microscopic mechanical reactions between the particles to model the nonlinear characteristics of the soil. Based on the homogenization theory and lattice model, the stress-strain relationship, strength criteria, and corresponding macroscopic mechanical parameters with respect to microscopic parameters for MICP-cemented sand are derived and verified by DEM simulation based on the regularly arranged particle assembly. The effects of key parameters, including cement content, initial void ratio, inherent anisotropy, and confining pressure, on the mechanical behaviors of MICP-cemented sand is investigated in detail, and the good agreement between the theoretical solution and laboratory test results validates the applicability of the theoretical solution for analyzing MICP-cemented sand.

Clay deposits typically exhibit significant degrees of heterogeneity and anisotropy in their strength and stiffness properties. Such non-monotonic responses can significantly impact the stability analysis and design of overlying shallow foundations. In this study, the undrained bearing capacity of shallow foundations resting on inhomogeneous and anisotropic clay layers subjected to oblique-eccentric combined loading is investigated through a comprehensive series of finite element limit analysis (FELA) based on the well-established lower-bound theorem and second-order cone programming (SOCP). The heterogeneity of normally consolidated (NC) clays is simulated by adopting a well-known general model of undrained shear strength increasing linearly with depth. In contrast, for overconsolidated (OC) clays, the variation of undrained shear strength with depth is considered to follow a bilinear trend. Furthermore, the inherent anisotropy is accounted for by adopting different values of undrained shear strength along different directions within the soil medium, employing an iterative-based algorithm. The results of numerical simulations are utilized to investigate the influences of natural soil heterogeneity and inherent anisotropy on the ultimate bearing capacity, failure envelope, and failure mechanism of shallow foundations subjected to the various combinations of vertical-horizontal (V-H) and vertical-moment (V-M) loads. (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/).

This article experimentally evaluates the influence of the sample preparation method on the undrained monotonic and cyclic response of a saturated Malaysian kaolin. Two different sample preparation methods were adopted: slurry consolidation and moist compaction. The results of undrained monotonic triaxial tests showed the same critical state friction angle regardless of the sample preparation method and overconsolidation ratio. Under undrained cyclic loading, the well-known reduction in the number of cycles required to reach failure conditions with increasing cyclic stress ratios was evident regardless of the sample preparation method. However, important qualitative differences were observed depending on the sample preparation method, such as the degree of inherent anisotropy manifested in terms of the inclination of the effective stress paths, and the asymmetric vertical strain accumulation in the stress-strain space. The reasons for the observed differences in behavior are analyzed and discussed in the manuscript.

Inherent (fabric) anisotropy is one of the most important properties of earthen materials that significantly influences their strength and stiffness characteristics. In this study, a comprehensive series of unconfined and constrained compression tests is performed on normally consolidated (NC) clay samples with different plasticity indices to examine the effect of inherent anisotropy on their mechanical characteristics. Accordingly, several cylindrical clay samples with different proportions of kaolinite and bentonite are reconstituted at a wide range of deposition angles, and then subjected to both unconfined and constrained compressive loadings. The experimental results reveal that, for a clay sample with a particular plasticity index, the highest and lowest values of unconfined compressive strength (UCS), secant modulus (E50), and constrained Young's modulus (Eoed) are associated with deposition angles of 0 degrees and 90 degrees, respectively. The results also show that at a certain bedding plane angle, the sample containing 30 % bentonite (PI = 110 %) exhibits the highest UCS, E50, and Eoed values. Several practical empirical correlations are developed to estimate the strength and stiffness properties of NC clays based on their plasticity indices and bedding plane directions. Furthermore, Scanning Electron Microscopy (SEM) analysis is conducted to explore the microstructure of samples containing varying percentages of kaolinite and bentonite.

This study aims to explore the significant impact of soil fabric anisotropy on the ultimate bearing capacity of eccentrically and obliquely loaded shallow foundations overlying a geosynthetic-reinforced granular deposit. For this purpose, the well-established lower bound theorems of limit analysis (LA) in conjunction with the finite elements (FE) formulations and second-order cone programming (SOCP) are exploited to perform the bearing capacity estimations. The consideration of the soil mass's inherently anisotropic response in the granular layer involves the utilization of distinct internal friction angles in various directions. The lower bound FELA framework adopted in this study incorporates both the pull-out and tensile mechanisms of failure in the reinforcement layer. The marked contribution of soil inherent anisotropy to the impacts of ultimate tensile strength (Tu) T u ) and embedment depth (u) u ) of the geosynthetic reinforcement on the failure mechanism, bearing capacity ratio (BCR), BCR ), and failure envelope of the overlying obliquely/eccentrically strip footing is rigorously examined and discussed. It is generally concluded that for a given embedment depth, failure envelopes of the surface footing in both V-H H and V-M M planes shrink appreciably with the increase in the soil anisotropy ratio as well as the decrease in the geosynthetic ultimate tensile strength. Moreover, the influence of soil inherent anisotropy on the overall bearing capacity of shallow foundations is more evident in the case of using strong reinforcement compared to the weak geosynthetic. The findings of this investigation demonstrate that overlooking the soil inherently anisotropic behaviour in the numerical analysis of shallow foundations would give rise to undesirable non-conservative and precarious designs.

This paper examines the impacts of deposition direction and density of granular soils on their large deformation behavior encapsulated by column collapse processes. We combine a critical state-based, anisotropic constitutive model for sand and material point method (MPM). The constitutive model includes state-and fabric-dependent dilatancy and hardening, thus accounting for the effects of density and deposition direction on the mechanical behavior of soils. The MPM model is first validated against experimental results. We then investigate the fundamental connections between local constitutive properties of soils (e.g., friction and dilation) and global column collapse response. Based on these correlations, this work further studies how material density and deposition direction influence collapse behavior, including run-out distance, residual height, and slope angle of the static region. Results indicate that run-out distance is relatively insensitive to initial soil density but can be significantly altered by the deposition direction of soils. Peak run-out distance is observed as the deposition direction is aligned with sliding band formed within the granular column. Moreover, a higher density or a smaller inclination of deposit direction leads to a greater residual height and a steeper slope of the static region. The mechanisms of above effects from soil properties perspectives are discussed.