Hardening–Softening Constitutive Model of Hard Brittle Rocks Considering Dilatant Effects and Safety Evaluation Index

Abstract

The damage and even failure of hard brittle rocks has been the most important challenge facing the safety of construction of deep engineering works, so the key to solving this problem is the recognition of the strength characteristics and description of the mechanical behavior of hard brittle rocks. Therefore, in view of this problem, in this study, we first analyzed the strength and mechanical response characteristics revealed in tests of, and site excavation in, hard brittle rocks. Second, by analyzing rock-strength envelopes on meridional and deviatoric planes, the generalized polyaxial strain energy (GPSE) strength criterion was applied. This allows description of the effects of the minimum principal stress, intermediate principal stress, hydrostatic pressure, and Lode’s angle of stress on the strength of hard rocks. By establishing evolutionary relationships of strength parameters and dilation parameters with plastic volumetric strain in rock failure, we established an elasto-plastic mechanical constitutive model for hard brittle rocks based on the GPSE criterion. In addition, through use of the failure approach index theory and the dilatancy safety factor, an evaluation index for degree of damage considering dilatant effects of rocks was proposed. Finally, the constitutive model established in this study and the proposed evaluation index were integrated into the numerical simulation method to simulate triaxial tests on rocks and numerical simulation of deformation and fracture of the rocks surrounding the deep-buried auxiliary tunnels in China’s Jinping II Hydropower Station. In this way, the reasonableness of the model and the index was verified. The strength theory and the constitutive model established in this research are applicable to the analysis of high-stress deformation and fracture of hard brittle rock masses, which supports the theoretical work related to deep engineering operations.