Numerical simulation of complete stress–strain curves of brittle rocks using 3D FDEM

Parameter calibration in 3D finite–discrete element method (FDEM) simulations remains challenging due to complex micro–macro relationships and the limited consideration of post-peak behavior in existing approaches. This study presents a calibration method constrained by complete stress–strain curves through a systematic sensitivity analysis of key model parameters based on numerical simulations of uniaxial and conventional triaxial compression tests. The results indicate that element size and loading rate mainly affect numerical stability and curve smoothness; Mode I fracture energy release rate controls post-peak brittleness; Mode II fracture energy release rate governs peak strength, residual strength, and the overall curve shape; and penalty parameters directly control elastic response deviations and numerical stability, while also significantly affecting peak and residual strengths. Based on these findings, a calibration framework is established by prioritizing experimentally measurable parameters and iteratively adjusting key parameters, while constraining numerical parameters within reasonable ranges based on parameter–response relationships to ensure consistency between input experimental parameters and macroscopic responses. This allows the experimental parameters to be directly used and reduces the number of parameters requiring calibration. Validation using experimental results from different rock types demonstrates that the calibrated model can reliably reproduce complete stress–strain curves and failure mode evolution under various confining pressures. The results demonstrate that the proposed method provides an efficient and practical approach for parameter calibration in 3D FDEM simulations of brittle rock failure.