Mechanical behavior and damage constitutive model of granodiorite in a deep buried tunnel

It is of great theoretical and practical significance to study the mechanical properties of deep rock for the construction of deep rock engineering. There have been few studies on the relationship between the macromechanics and microdamage of deep hard rock and few reports on damage constitutive models of rock with full consideration of residual strength. The macroscopic mechanical behavior of granodiorite in a deep tunnel in western China was studied by uniaxial and triaxial compression tests in the laboratory. On this basis, the damage nature of the rock is fully analyzed and a microdamage constitutive model of the rock considering the residual strength characteristics is established by coupling the macromechanical behavior with the microdamage mechanism. Finally, the damage evolution process of the rock is analyzed. The results show that the confining pressure has a significant effect on the deformation failure characteristics and damage mechanism of the rock. With increasing confining pressure, the damage of the rock is restrained, and the failure mode of the rock transforms from tensile failure and tensile-shear failure to shear failure. The proposed damage constitutive model with definite physical meaning can fully reflect the whole deformation and failure process of the rock, including residual strength characteristics, and the results are in good agreement with the test results. The damage evolution process of the rock can be divided into an undamaged stage, a damage acceleration stage, a damage deceleration stage, and a complete damage stage. The analytical method of combining macro- and micromechanics mechanisms in this paper is reasonable, and the research results provide a theoretical reference for the construction of deep rock engineering.