Discrete Element Simulation of Axially Compressed Energy Constitutive Relations in Defective Sandstone

In order to investigate the energy evolution and mechanical behavior of defective sandstone under uniaxial compression, the discrete element method (DEM) is employed. Effects of different rock bridge inclination angles and distances on the mechanical behavior of defective sandstone are systematically studied by DEM, and established a damage constitutive equation based on energy dissipation. The results indicate that the rock bridge inclination angle and distance significantly affect the mechanical response and failure modes of defective sandstone. Large inclination angles (60°, 90°) facilitate crack propagation along the direction of maximum principal stress, while small inclination angles (0°, 30°) increase the proportion of shear cracks, leading to different failure patterns. Additionally, the elastic modulus and compressive strength exhibit a “U” -shaped nonlinear characteristic with the variation of inclination angle and distance. Moreover, the energy evolution pattern depends on the rock bridge inclination angle. The total energy and dissipated energy first decrease and then increase with increasing rock bridge inclination angle, and peaking at 90°. The influence of rock bridge distance on energy varies with inclination angle. For angles less than 45°, the two types of energy decrease with increasing distance. For angles greater than 45°, the two types of energy first increase and then decrease. The three-stage characteristic of the elastic energy dissipation ratio can serve as a predictive indicator of the instability of defective sandstone. Furthermore, the energy dissipation damage constitutive model constructed based on dissipated energy can accurately describe the deformation and failure behavior of defective sandstone under different rock bridge parameters. This model has significant application potential in practical engineering, but it needs to be adjusted according to specific stress conditions to optimize prediction accuracy. The research results can provide theoretical references for disaster prevention in geotechnical engineering.