Research on the effects of heating and cooling processes on the mechanical properties of yellow rust granite

Geological hazards caused by high-temperature rocks cooling down after encountering water are closely related to underground mining and tunneling projects. To fully understand the impact of temperature changes on the mechanical properties of rocks, yellow rust granite samples were subjected to heating-natural cooling and heating-water cooling cycles to experimentally study the effects of these processes on the mechanical properties of the samples. The mechanism of the heating-cooling process on the macromechanical properties of the rock was discussed. Based on the Drucker-Prager criterion and Weibull distribution function, a damage variable correction factor was introduced to reflect the post-peak strain softening characteristics, and a thermo-mechanical coupled damage constitutive model of the granite was established. The results showed that in the natural cooling mode, the mechanical properties deteriorate significantly when the temperature exceeded 600 ​°C, and the failure mode changed from brittle failure to ductile failure. In the water cooling mode, the peak strength and deformation modulus increased at temperatures below 400 ​°C with an increase in the cycle number, while at 600 ​°C, the peak strength and elastic modulus notably decreased. The peak strain increased with the increase of the cycle number and temperature at all temperatures, and the failure mode of the granite tended to change from tensile failure mode to shear failure mode. The experimental results were used to validate the damage constitutive model. The shape parameter r and scale parameter S in the Weibull distribution function of the model were used as indicators to reflect the brittleness degree and peak strength. This study helps to understand the behavior of rocks in high-temperature environments, in order to prevent and mitigate potential geological hazards.