Gouge Particle Evolution in a Rock Fracture Undergoing Shear: a Microscopic DEM Study

Abstract

The evolution of gouge materials in rock fractures or faults undergoing shear can change fracture properties in terms of shear strength and dilation, fluid transmissivity and retardation for contaminants. In order to conceptually understand gouge mechanical behaviors including movement, microcracking, abrasion and redistribution, particle mechanics models were used to simulate single- and multi-gouge particles in a rough fracture segment undergoing shear. The results show that gouge particles behave in two different ways under low and high normal stresses, respectively. Under low normal stress, gouge particles mainly roll with the moving fracture walls, with little surface damage and small dilation during the shear process. Under high normal stress, gouge particles can be crushed into a few major pieces and a large number of minor comminuted particles, accompanied by more severe damage (abrasion and microcracking) in fracture walls and continuous fracture closure. The modeling results were also compared with published experiments and used to explain the observed macroscopic behaviors of rock fracture undergoing shear. The effects of microparameters used in the particle mechanics models on the simulation of gouge behaviors were also investigated through sensitivity analysis.