Effect of Bedding Structure and Homogeneity on the Shale Failure: Insights From Weibull‐Based Discrete Element Method (DEM) Modeling

Shale, a sedimentary rock with significant heterogeneity and well‐developed bedding structures, exhibits complex mechanical behaviors and failure mechanisms. In this study, the Discrete Element Method (DEM) is employed to develop a Weibull distribution‐based parameter assignment approach for simulating heterogeneous shale specimens under uniaxial compression. The mechanical responses and fracture evolution are systematically analyzed, and a novel damage constitutive relation is proposed that accounts for both material heterogeneity and bedding structure effects. The results show that: (1) the stress‐strain curves consist of three stages: linear elasticity, nonlinear crack propagation, and brittle failure. The peak strength follows a power–law relationship with the homogeneity index ( m ), and at higher homogeneity levels ( m ≥ 8), enhanced stress uniformity delays post‐peak stress reduction. At a 90° bedding angle, the mechanical response transitions to bedding‐plane‐dominated ductile deformation, with reduced sensitivity to homogeneity. (2) The failure mechanisms are governed by dual control effects: at bedding‐dominated angles (60°–90°), tensile fracturing along bedding planes predominates and is weakly affected by homogeneity, while at co‐controlled angles (0°–45°), failure patterns evolve with increasing m , progressing through V‐shaped, inverted V‐shaped, and oblique L‐shaped fractures. (3) Stress‐strain curve fitting using the proposed damage constitutive relation demonstrates strong consistency with simulation results for m > 2. These findings provide a quantitative framework for assessing damage thresholds in shale with varying homogeneity and bedding angles, offering valuable guidance for shale‐related engineering projects.