A thermo-mechanical damage constitutive model for deep rock considering brittleness-ductility transition characteristics

This paper developed a statistical damage constitutive model for deep rock by considering the effects of external load and thermal treatment temperature based on the distortion energy. The model parameters were determined through the extremum features of stress - strain curve. Subsequently, the model predictions were compared with experimental results of marble samples. It is found that when the treatment temperature rises, the coupling damage evolution curve shows an S-shape and the slope of ascending branch gradually decreases during the coupling damage evolution process. At a constant temperature, confining pressure can suppress the expansion of micro-fractures. As the confining pressure increases the rock exhibits ductility characteristics, and the shape of coupling damage curve changes from an S-shape into a quasi-parabolic shape. This model can well characterize the influence of high temperature on the mechanical properties of deep rock and its brittleness-ductility transition characteristics under confining pressure. Also, it is suitable for sandstone and granite, especially in predicting the pre-peak stage and peak stress of stress - strain curve under the coupling action of confining pressure and high temperature. The relevant results can provide a reference for further research on the constitutive relationship of rock-like materials and their engineering applications.