Macro‐Meso Characteristics and Evolution Mechanism of Strain Localization Behavior in Soil Based on the Finite and Discrete Element Methods

The macro‐ and meso‐mechanical behaviors associated with strain localization in soils were thoroughly investigated using the finite element method (FEM) and the discrete element method (DEM), respectively. First, an elasto‐plastic constitutive model based on micropolar theory was developed, highlighting the influence of internal length parameters on the width of the shear band. Additionally, an algorithm was proposed for identifying and calculating the orientation and width of the shear band using the DEM. On this basis, the linear parallel bond model in the PFC (Particle Flow Code) software was used to analyze the effect of particle diameter on the shear bands. The research summarized the potential relationships among particle diameter, internal length scale, element size, and shear band width. It also addressed how the aspect ratio (height‐to‐width ratio) and boundary conditions of the specimen in the biaxial compression test impact the formation of shear bands. Findings indicated that the shear band width ranged from 6 to 15 times the particle diameter or internal length scale, and that the element size should not exceed five times the internal length scale to ensure mesh‐independent results. Different boundary conditions were shown to result in varying shear band modes, including single inclined types, “X” types, or diffuse types. Furthermore, a calibration framework for the meso‐parameters was established and validated, providing a crucial link between macro‐ and meso‐material models.