Permeability Evolution in a Fracture in Granite During Isotropic Compression

The permeability evolution of fractures in geologic media plays a pivotal role in various geo-mechanical activities, ranging from energy resources recovery to the deep geologic disposal of hazardous materials. This paper presents both laboratory and computational investigations into the evolution of fracture permeability under the influence of varying confining stress levels in a crystalline granitic rock from the Canadian Shield. Steady state permeability experiments were conducted to assess variations in fracture permeability in areas where stress conditions may significantly change due to large-scale underground excavations. A high accuracy laser scanner was used to capture the geometric features of the fracture surface, enabling the numerical simulation analysis of stress-induced hydromechanical behavior. The fracture permeability evolution was systematically investigated under both isotropic stress and deviatoric stress conditions, including four loading–unloading sequences and a series of sequentially increased deviatoric stresses. Simulations of fracture closure under increasing confining pressure and corresponding fluid flow process were performed incorporating a model constructed from fracture elevation data obtained through scanning. The results demonstrate a reduction in permeability exceeding 50% as the triaxial confining stress increases from 5 to 40 MPa. Additionally, permeability hysteresis during stress relief was observed. These findings are relevant to deep geological construction activities where excavation leads to the development of an excavation damage zone and stress alterations, affecting overall fluid flow process.