Study on the geometric characteristics effect of contact area on fracture seepage

Abstract

Seepage in rock fractures is influenced by the geometry of the contact area. A parallel model with two circular cylindrical contact areas is studied by numerical simulation. The variation of the seepage field in the fracture model is analyzed by changing the size (radius r) and location (mutual distance s and upstream angle θ) of the two contact areas. Changing r, s, and θ is essentially changing the width and angle of the flow channel on both sides of the contact area. The contact area compresses the flow channel so that there is an obvious pressure drop around the contact area, and the reduced pressure potential energy is mainly converted into the kinetic energy of flow around the contact area and the water flow obtains a larger velocity. The resulting inertial effect controls the generation and development of the low-velocity region and eddy behind the contact area. θ is about 30°, which is the critical point of eddy current generation behind the contact area, the changing trend of −∇ P and s and −∇ P and sin θ. Two conceptual models are proposed that there is a quadratic function relationship between −∇ P and s, and an exponential function relationship between −∇ P and sin θ. The parameter N is proposed to represent the joint action of two kinds of the flow channels (the flow channel between contact area and contact area and the flow channel between contact area and lateral wall) and the relationship between −∇ P and N is a quadratic function.