Influence of Inclination of En‐Echelon Joints on Shearing Behavior of Crystalline Rock

Abstract

Stability of rock masses in rock slope is significantly threatened by the presence of en‐echelon joints. Most previous studies focus on artificially jointed rock mass, and lonely a limited research has been conducted on the shearing performance of crystalline rock possessing en‐echelon joints. In this study, a modified grain‐based model (GBM), which considers the shape of feldspar in real rock, is used to investigate the effect of en‐echelon joint angle on the strength behavior and the associated micro‐cracking evolution of crystalline rock under different normal stresses. The simulation results indicate that peak shear strength and the principal direction of anisotropy generally reach their maximum values at en‐echelon joint angle of −15°. Micro‐cracks typically initiate at the tips of en‐echelon joints, and the connecting pattern between these joints is notably affected by joint angle. The results reveal that, despite exhibiting a high microscopic damage ratio, the shear strength of the rock specimen with negative en‐echelon joint angle increases due to enhanced inter‐particle friction and mechanical interlocking under compression. On the other hand, positive joint angle induces disc separation and rotational failure, which reduces shear resistance. In addition, an increase in normal stress amplifies the damage ratio among all joint angles. By analyzing the disc displacement field using fracture mechanics, this study reveals how joint angle and normal stress affect the propagation of wing cracks and secondary penetration cracks between en‐echelon rock joints. The research provides valuable insights into understanding the failure mechanism of rock with en‐echelon joints.