Permeability Evolution and Gouge Formation During Fracture Shearing

Hydro‐mechanical processes are crucial in shear‐controlled geoscientific applications such as enhanced geothermal systems and often result in stress‐dependent permeability changes. The present study aims to investigate shear‐induced permeability evolution of a natural sandstone fracture using a novel modeling approach. Combining a mechanical discrete element model and a hydraulic finite element model, three normal stress‐related hydro‐mechanical regimes can be identified. Under low normal stress conditions (<4.0 MPa), permeability is enhanced during shearing due to dilation on intact asperities. With increasing normal stress, asperities break and gouge is formed, leading to a normal stress‐related transition where permeability tends to decrease during shearing. In our study, this transition occurs when normal stress equals the rock's ultimate tensile strength (4.0 MPa). For normal stresses >4.0 MPa, permeability decreases during shearing due to intense fracture surface damage.