Discrete Element Modelling (DEM), employing the replacement method, has been extensively utilized to investigate the micro and macroscopic behavior of soil with particle breakage. Despite numerous breakage criteria proposed in the literature, an agreement on the most appropriate criterion remains unclear. In this study, three-dimensional DEM analyses were conducted using Particle Flow Code (PFC3D) to assess stress distribution and identify potential locations of particle crushing during direct shear tests for coarse sand subjected to different high normal stresses. The investigation focused on employing a breakage criterion featuring Weibull distribution of particle strengths and considers the effect of particle size on average strength to predict the occurrence of fractures. Various breakage criteria, including major principal stress, mean stress, octahedral shear stress within a particle, and stress calculated from the maximum contact force on a particle, were each examined. The findings indicate that potential crushable particles were predominantly situated near diagonal shear band. Notably, results demonstrate that criteria based on octahedral shear stress and maximum contact force prove more effective in accurately reproducing the concentration of crushed particles near the shear band.

This paper explores the effect of particle breakage on the mechanical behavior of coarse sand through 3D Discrete Element Method (DEM) simulations of direct shear tests (DST). The objective is to gain insights into the macro- and micro-mechanical behaviors of crushable coarse sand, with a particular focus on the stress–strain relationship, volumetric deformation, and evolution of grain crushing. The simulations involve a comparison between non-crushable and crushable particle models, where the crushable particles are implemented in the shear zone of the DST subjected to different high normal stresses. The findings indicate that the crushable particles experience partial crushing at peak shear stress, with further particle crushing leading to the production of finer particles at the shearing plane during shearing at the critical state. The migration of these finer particles under pressure and gravity generates their accumulation predominantly in the lower section of the simulation box. Importantly, the presence of crushing in the DST induces a decrease in the shear stress and an increase in the volumetric strain leading to contractive behavior instead of dilation, which gradually stabilizes the volumetric deformation at higher normal stresses.

In this paper, numerical computations using PLAXIS 2D and 3D have been conducted to optimize a row of piles in cohesive-frictional slope stabilization. First, 2D parametric studies were performed to identify both the optimal location and length of the pile as well as the effect of pile head conditions. Next, more rigorous parametric studies taking account of the exact geometry was carried out using 3D analyses. According to the obtained results, the fixed pile head located at the slope middle better improves the stability and reduces the optimal length of the pile. Piles with free head contribute marginally to the increased factor of safety of cohesive-frictional slope. In 3D analyses, it is shown that spacing ratio beyond S/D = 4 (S: pile spacing, D: diameter of the pile), the soil will flow between piles leading to a total vanish of the arching effect when S/D exceeds 12. Comparing the results, the limitation of 2D analysis for piled cohesive-frictional slope is highlighted.