Permeability evolution of fracture during slipping under normal stress condition
Fractures are the main pathway for fluids in the formation, which closely related to the oil and gas production, CO2 geological storage, enhanced geothermal system and nuclear waste disposal. Under the condition of stress, fractures will slipping along its axial, then hydraulic characteristics of that be changed and influences the flow behaviours of these projects. Therefore, the permeability evolution of a fracture is a key scientific problem for the hydraulic characteristic rock mass. To further understanding the permeability variation of a fracture during slipping under normal stress, the permeability of an artificial granite fracture during slipping was measured. The variation of permeability with shear displacement, and the relationship between shear stress/normal deformation and slipping displacement obtained by the shear-flow tests. Shear slipping affects significantly the permeability of the fracture, and the variation trend of permeability depends on the level of normal stress. In low normal stress, the fracture permeability is enlarged tens of times in the stage I and II, with a weak drop in the early. For the high normal stress, the fracture permeability is falling consistently. In the stage III, the fracture permeability is all significantly reducing. The high normal stress not only limits the dilatancy of the fracture but also enhances the formation of fault gouge. Therefore, the fracture permeability decreased by shearing under high normal stress.