Temperature effect of rockburst in granite caverns: insights from reduced-scale model true-triaxial test

Abstract

AbstractTo investigate the influence of thermal treatment on the rockburst in granite caverns, true-triaxial compression tests were conducted on pre-heated granite cubic samples containing a circular through-hole using a true-triaxial test system, and the micro camera was used to monitor and record the rockburst process in realtime. Test results show that the uniaxial compressive strength and elastic modulus first increase and then decrease as the temperature increases, which reach the maximums at 200 °C and sharply decrease at temperatures from 400 to 600 °C. The density and P-wave velocity decrease and the peak strain increases with increasing temperature. The main failure mode is X-shaped shear-tension failure at 25 and 200 °C, and single-slope shear failure at 400 and 600 °C. Thermal treatment exhibits slight effect on the rockburst incubation process in granite caverns. The stress required for rockburst decreases when the temperature increases or decreases from 200 °C. The higher the temperature, the lower the required stress. At 25 and 200 °C, rockburst is violent, and fine particles and large slabs are mainly produced; at 400 and 600 °C, the intensity of rockburst is relatively weak, and fine particles are mainly generated. Thermal treatment exhibits double effects on rockburst. The mechanism of thermal treatment on granite rockburst is the strengthening effect caused by water loss and the weakening effect caused by thermal expansion cracking. This study can provide theoretical guidance for the stability analysis and rockburst prevention of temperature-affected granite caverns.