Experimental Study and Modeling of Fracture Aperture Evolution Under Confining Pressure Loading-Unloading

Fracture is the main seepage channel of rock mass, and its aperture is an important factor affecting the permeability of rock mass. Fracture aperture changes with the surrounding load, which results in changes in rock permeability. In order to find out the evolution characteristics of fracture aperture, the confining pressure loading and unloading tests were carried out on the intact specimens and the fractured specimens; Through test data analyzing and processing, the relationship curve between confining pressure and fracture aperture was obtained; based on the definition of joint stiffness, the normal stress-aperture relationship model is derived. The results show that the deformation of rock matrix is mainly linear elastic, and the fracture deformation is irreversible plastic deformation. With the increase of pressure, the fracture aperture decreases. The reduction is severe at the beginning of loading, and slows down with the increase of confining pressure. When the confining pressure reaches the closure pressure, the fracture aperture tends to zero. The normal stress-fracture opening relationship model based on joint stiffness can better reflect the relationship between fracture aperture and confining pressure measured in actual tests. The research results can provide reference for prediction and evaluation of permeability characteristics and evolution behavior of fractured rock mass.