Experimental Evaluation of Fluid Flow through Artificial Shear Fracture in Granite

Abstract

Direct shear tests were performed for intact granite samples to prepare specimens containing single shear fractures created under 20, 40, 60 MPa normal stress and 1, 3, 5 mm shear displacement conditions, for flow-through experiments. Shear fractures were successfully created on the constrained fracturing plane. Different normal stress and shear displacement conditions caused different roughness of fracture surfaces. Flow-through experiments were performed for the specimens containing shear fractures under 10-100 MPa confining pressure conditions. In the case of the shear fractures created under 20, 40 MPa normal stress and 1, 5 mm shear displacement conditions, no obvious differences were observed in permeability despite different normal stress and shear displacement conditions. Permeability decreased significantly under low confining pressure conditions (< 40-50 MPa), and then slightly decreased with increasing confining pressure. In the case of the shear fractures created under 60 MPa normal stress and 1, 3, 5 mm shear displacement conditions, on the other hand, permeability differed from the above case. It was observed that permeability decreased drastically under high confining pressure conditions (> 70 MPa). It was also observed that permeability increased clearly with increasing shear displacement condition.