Creep energy damage model of rock graded loading

A triaxial creep test of the surrounding rocks in the Fuxin Hengda coal mine was performed using an MTS815.02 rock mechanics testing system. The damage variable of the rocks was deduced on the basis of the energy conservation law and minimum energy consumption theory. A nonlinear creep damage model was established. Results indicated that the internal porosity of the rocks is completely opened at the initial moment. The rocks demonstrated a certain amount of instantaneous deformation during the loading of pore compression closure. In addition, rock cracks developed and expanded with the complete closure of pores and an increase in stress. The axial and radial deformations of the rocks also increased dramatically. The established nonlinear creep model of rock damage can clearly reflect the law of stress and strain changes. Energy dissipation was also observed in damaged rocks. The new model can compensate for the shortcomings of traditional models that are difficult to describe in the accelerated creep phase. The final test and fitting curves presented high degrees of fitting. Thus, the reflection of the deformation law of the entire rock creep process by deriving the energy of the damage evolution equation is suitable and feasible.