Characterization of shear-flow behaviors of rock fractures using a newly-developed shear-flow apparatus

Abstract To investigate the hydraulic characteristics of rock fractures during sliding, we designed and fabricated a novel apparatus for conducting shear-flow tests. The apparatus was mainly composed of a servo-controlled loading system, a specially-designed pressure vessel, confining pressure loading system, and fluid control system. It can apply a maximum confining pressure of 20 MPa and a fluid pressure of 10 MPa while achieving a maximum shear displacement of ∼10 mm. Specialized monitoring sensors enable direct measurement of the sample normal displacement. The test results revealed that the fluid flow in rough fractures in granite is highly nonlinear, and is affected by factors such as fracture roughness, dilatancy of fractures, and gouge production during shearing. In addition, the synchronous change in the normal displacement and fracture slip rate during the quasi–static slip stage of the hydro-shearing test demonstrates the dependency of the normal displacement on the slip rate, which is consistent with previous studies. The apparatus provides a reliable platform for future shear-flow tests on rock fractures under various operating and experimental conditions.