Mechanisms of Fracture Propagation and Permeability Evolution in Brittle Rock Under Unloading: A Coupled Discrete Element–Porous Finite Volume Numerical Framework

ABSTRACT This study presents an innovative approach to simulating brittle rock behavior under unloading conditions using an improved discrete element method (DEM) that incorporates the particle interlocking effect. By expanding the interaction range between particles, the model enhances the pressure ratio and internal friction angle of the rock, overcoming the limitations of traditional DEM models in simulating the nonlinear failure envelope of brittle rock. A weighted Delaunay triangulation technique is employed to discretize the rock medium, enabling a more refined mesoscopic‐scale representation. A coupled discrete element method–porous finite volume (DEM–PFV) solid–fluid interaction model is then developed to simulate the fluid flow through fractured rock, offering a more accurate depiction of solid–fluid interactions at the microscopic scale. The study explores the effects of different initial axial pressures, confining pressures, water pressures, and fracture angles on the deformation, strength, fracture, and propagation of brittle rock under unloading conditions. Additionally, it investigates the flow and damage mechanisms of fractured rock under high‐stress and high‐water‐pressure conditions, revealing the complex interplay between fluid dynamics and fracture propagation in deep fractured rock. The results provide valuable insights into the failure mechanisms and fracture penetration of fractured rock, with potential implications for geological engineering, resource extraction, underground fluid management, and disaster prevention in deep rock environments.