Discrete Element Simulation on Mechanical Behavior and Fracture Evolution Mechanism of Regular Joint Rock Under Triaxial Compression

Abstract

To investigate the mechanical and failure characteristics of jointed rock masses under external loads, this study established a three-dimensional numerical model using the discrete element method PFC (particle flow code) based on conventional triaxial tests of jointed rock samples. A novel contact assignment method was employed to enhance computational efficiency, effectively reproducing the mechanical behavior of jointed specimens. The influences of confining pressure, joint roughness coefficient, and joint dip angle on the strength and deformation properties of the rock mass were systematically examined. By integrating force chain strength analysis with crack development, the post-failure particle displacement field and internal stress distribution patterns were revealed. The numerical simulation results accurately replicated the strength and deformation characteristics of jointed specimens under triaxial loading conditions, demonstrating a significant transition in failure mechanisms with varying joint dip angles: from matrix-dominated failure to shear slip failure along the joint surface. An increase in joint roughness was found to markedly enhance the integrity of the specimen, while force chains primarily aligned along the normal direction of the joint surface. High stress concentrations observed on the joint surfaces rendered them more susceptible to failure during loading. To account for the bonding characteristics between the upper and lower rock blocks in the specimens, this study extended the Ladanyi shear strength criterion, making it more suitable for strength characterization under such bonded joint conditions.