A Unified Deterioration Model for Elastic Modulus of Rocks with Coupling Influence of Plastic Shear Strain and Confining Stress

A reasonable prediction of the elastic modulus of rock and rock mass can provide sound basis for the design in tunnels and underground caverns. It is observed from the laboratory results that the elastic modulus not only depends on the confining pressure but also indicates certain sensitivity to the failure degree during the loading-fracturing process. This paper deduces a unified expression for the elastic modulus with the coupling effects of the plastic strain and confining stress, and fits the soft, moderate, hard rocks with different quality. In this paper, a method to determine the elastic modulus from the laboratory results is proposed. Through the method, the variation of the elastic modulus versus the plastic strain and confining stress for the soft, moderate, hard rocks is analysed. A unified deterioration model for the elastic modulus is developed by the nonlinear fitting regression method. This deterioration model can be employed in the analytical and numerical analysis of the tunnels and underground caverns, which enables to present a more realistic mechanical behaviour of rock mass.