Study on the slip characteristics of rock inhomogeneous friction interface

Abstract

Theory assumes that the friction along the discontinuous interface is uniform, and the selection of uniform distribution of friction resistance along the interface is a simplification of the actual physical process. This assumption leads to unsafe design. Therefore, the numerical simulation and experimental methods are used to study the slip of the discontinuous interface with non-uniform friction. This study used a numerical model comprised of two blocks with completely matching contact interfaces. The friction coefficient of one part of the contact surface differed from that of the other, resulting in a non-uniform friction interface. The model was simulated under biaxial compression. First, a normal load of 3 MPa was applied, followed by a shear load until the contact interface slipped. The initiation and propagation of slippage at the contact interface and the changes in the stress field at the slippage contact interface were monitored. The slip started from the area with low frictional strength and gradually expanded to the area with high frictional strength with increasing shear load. The transfer of the slip from an interface with a small friction coefficient to a high friction strength resulted in stress concentration at the interface of the non-uniform friction interface. Engraving using an engraving machine produces a discontinuous interface in which one part of the interface has high friction strength, whereas the other part has low friction strength. The shear load is applied using a shear instrument to cause the discontinuous interface to slip. At the same time, DIC monitored the displacement of the discontinuous interface. The comparison found that the rule of the experimental results is the same as that of the numerical simulation. Reinforcement measures (enhanced friction strength) for areas with low friction strength can effectively prevent slip damage. Based on the distribution of shear stiffness of the rock discontinuous interface, the friction properties of the entire fracture interface can be obtained to accurately identify areas with low frictional strength, and targeted reinforcement measures should be carried out to prevent slip damage.