STUDY OF CONSTITUTIVE MODEL FOR ROCK INTERFACES AND JOINTS UNDER CYCLIC SHEAR LOADING

The tests and numerical models of rock interfaces and joints under cyclic shear loading are reviewed, and a new constitutive model is developed. When the contact state is stick, the joint loading follows conventional hyperbolic response, and unloading follows linear response. When the contact state changes from stick to slide, the friction degree falls from pick to residual in terms of hyperbolic function. The dilation relation, which causes coupling of the normal and shear responses, is described by dilation degree, and the contact stiffness matrix is established. The dilation curve is composed of subsections of parabolic curves, which are calculated from initial and residual dilation degree. The wear of the contact surface in cyclic loading influences the friction and dilation character of the interfaces and joints, new friction degree and dilation degree after surface damage are calculated according to each exponential function of shear plastic work. This model describes the physical significance of rock interfaces and joints under cyclic shear loading. The prediction agrees with test responses.