With the acceleration of urbanization, the stability of the foundation is being more crucial to the performance and service of the superstructure. As our understanding of the factors influencing soil's physical and mechanical behavior deepens, it becomes increasingly challenging for traditional limit equilibrium and limit analysis methods to accurately consider the complex factors affecting foundation stability, such as initial fabric anisotropy caused by the particle morphology and geological deposition in sand. Although some scholars had used advanced constitutive models in the finite element method (FEM) to investigate the influence of initial fabric anisotropy on mechanical responses of foundations, this approach failed to reveal the microscopic information underlying the shear failure of sandy soil foundations. In this study, the influence of the initial fabric anisotropy of sandy soil on the ultimate bearing capacity and shear failure mode of shallow foundation is studied using the hierarchical FEM and discrete element method (DEM) coupling analysis method. Four representative volume elements (RVEs) with varying initial bedding plane angles are constructed in DEM for characterizing different initial fabric anisotropies, and the specific stress-strain information of DEM RVEs is directly passed into the corresponding Gauss points in FEM to replace the conventional constitutive model. Numerical results show that the initial fabric anisotropy affects the ultimate bearing capacity and shear failure mode of shallow foundations significantly, and the corresponding micromechanical behaviors at different local Gauss points have been explored, which advances our understanding of the micromechanisms underlying the progressive shear failure of sandy soil foundations significantly.

The tribological process between the tillage tools and the soil is quite complex. Wear on tillage tools changes depending on the material of the tool, opposing material (soil), environment (moisture, temperature), and dynamic factors (stress on sliding surface, sliding time, sliding speed, and sliding type). Chemical composition, microstructure, and mechanical properties of the material from which the tools are made; soil properties such as texture, structure, density, moisture, rock and gravel content; operating conditions such as tillage speed and depth; geometry and surface roughness of the tool, and impact angle with the soil are effective on wear. It is generally accepted that tillage tools go through low-tensioned and two-body abrasive wear. The ratio between the hardness of the tools (Hs) and the hardness of the abrasive soil particles (Ha) determines wear mechanisms. When this ratio is lower than 0.8, microcutting and microplowing mechanisms are dominant. Meanwhile, when the hardness value of the tool's surface is close to or higher than the hardness value of the soil particles, microcracks, fragmentation, and peel-off of the hard phases occur. Therefore, hardness alone may not be sufficient to ensure tribological performance, and hardness and toughness should be balanced since tillage tools are exposed to movements such as impacts.