A true triaxial creep constitutive model of rock considering the coupled thermo-mechanical damage

Abstract

The main emphasis in contemporary mineral resource extraction has shifted towards deep Earth resources to address economic development requirements. The influence of temperature has emerged as an undeniable factor as engineering projects delve deeper into the Earth. The definition of a damage variable, which considers the coupled thermo-mechanical damage, has been proposed within the framework of damage mechanics. This definition aims to accurately describe the different stages of rock creep behavior in high-temperature environments. Furthermore, a constitutive model has been developed to describe the creep behavior of rocks under the combined influence of temperature and true triaxial stress. This model considers the series connection of the elastic body, nonlinear Kelvin body, Heard body, and visco-elastic-plastic body. The model has been parameterized and validated using available creep test data, and the equation for the yield surface of rocks under true triaxial stress has been derived through data fitting. The findings suggest that the developed constitutive model is capable of accurately describing the properties of rock creep behavior at different stages in high-temperature conditions, thus confirming its rationality and precision.