Exploration of continuous rheological model for rock under uniaxial compression based on phenomenological damage theory

The analysis of rock damage under the thermodynamic framework is a research method in continuum damage mechanics. In this method, the coupling relationship between energy and damage is proposed to establish the damage constitutive model of rock from the perspective of phenomenological damage theory. Based on this idea, under the constraint of the law of energy conservation, the evolution process of the damage variable of rock under external load is deduced. Based on the quasi-static damage model, the dynamic damage hypothesis combined with damage driving force theory is proposed to establish a continuous rheological model. The creep processes under uniaxial compression of Shanqing coal and sandstone are simulated, and the long-term strength can be predicted by the proposed model. Finally, the simulation of stress relaxation behavior is also explored in this work. The comparison results show that the proposed model could describe the time-varying behavior of rock under uniaxial compression.