Abstract:Rock is a typical brittle non-uniform material that is rich in various internal defects (cracks, pores, joints fissures), which make the rock damage and failure mechanism very complex. Theoretical and laboratory experimental studies indicate that energy plays an important role during rock deformation and failure and abrupt energy release causes rock failure. Under certain conditions, this energy release can constitute an energy dissipation catastrophe. From the thermodynamics perspective, the process of rock damage is irreversible and energy release, the essential characteristic of rock deformation and failure, reflects the process of the propagation of internal defects and decreasing strength. The process of rock damage is one of constant energy evolution, so rock deformation and fracture can be well described from the energy viewpoint. Based on previous studies of rock damage, we know that the elastic modulus decreases while plastic strain emerges in the loading process. Based on the above analyses, we can define the damage variable with respect to energy. By relating the effective and total stress in the unloading stage of the stress-stain curve, we can determine a method for calculating the damage modulus. We conducted a statistical analysis of the damage parameters of rock under uniaxial and triaxial states to calculate and contrast the damage moduli. The results show the damage modulus to have a gradual decreasing trend with increasing confining pressure, whereby the damage modulus first decreases and then tends to stabilize. In addition, our method for calculating the damage modulus takes full account of the influence of the confining pressure. Building on the studies mentioned above, the analysis results of this paper promote further understanding of rock damage and failure.
