An improved equivalent constitutive model for layered rock mass considering layer structure and the effect of asymptotic deterioration of deformation and strength

As a kind of widely exposed engineering rock mass, layered rock mass exhibits extremely anisotropy and significant asymptotic deterioration effect in both deformation and strength. Its mechanical characteristics, excavation and support theory are of great significance to the guidance for engineering construction. In this paper, an equivalent constitutive model for layered rock mass considering layer structure and the effect of asymptotic deterioration of deformation and strength is proposed. The secondary development of equivalent constitutive model is realized by C++ program. In this model, layered rock mass is regarded as a transversely isotropic body before failure takes place. The controlling role of layer structure on mechanical behavior of rock mass during the damage failure process is highlighted. And the transformation relationship among deformation parameters under global coordinate system, local coordinate system and principal stress spatial coordinate system is established. The three mechanical parameters, namely elastic modulus(E), cohesion(c) and internal friction angle (phi) are regarded as function of equivalent plastic strain. Then the applied range and limitations of the equivalent constitutive model are briefly discussed. Preliminary validation of the equivalent constitutive model are carried out by the comparison of theoretical solutions, analysis of numerical test results, comparison of laboratory test results and simulation of excavation of circular tunnel, which indicate that the equivalent constitutive model has a good application prospect in analyzing deformation and failure mechanism of underground caverns related to layered rock mass.