Influence of Aperture on Shear Behavior of Non-Persistent Joint: Insights from Grain-Based Modeling

In the field of geomechanics and geotechnical engineering, joint is crucial as a common structure or flaw in rock material. The shear deformation, strength, and failure behavior of rock are significantly influenced by the structural properties of joints, which include arrangement, persistency, dip angle, and length. The shear strength and deformation behavior, as well as the related micro-cracking process of a collection of 2D jointed rock masses with varying joint persistency and joint apertures under various normal stresses, are numerically investigated in this study using an improved grain-based model (GBM) considering feldspar shape. The results show that joint persistency and normal stress have a larger influence on the shear strength and micro-cracking behavior of rock when compared with joint aperture. In particular, the crack initiation stress (CIS) is not greatly affected by joint aperture, while the direct shear strength (DSS) and the shear modulus (G) slightly decrease with the increase of joint aperture. The developed micro-cracks initiate primarily at both ends and the center of the rock bridge at the initial loading stage. The results from quantitative analysis of vertical stress of the numerical model reveal that higher joint persistency and lower normal stress result in a more uniform stress distribution. The influence of joint aperture, joint persistency, and normal stress on shear mechanical behavior and the micro-cracking mechanism of rock is theoretically explained through macroscopic and microscopic force analysis.