True triaxial tests on rockburst of granite after high temperatures

The rockburst ejection process of coarse-grain granite after high temperature of 200℃~700℃ and normal temperature of 25℃ are studied by using the self-developed true triaxial rockburst test system. By monitoring the rockburst process with the high speed system and the acoustic emission system, the rockburst ejection process, damage morphology, peak stress, acoustic emission characteristics, fragments feature and kinetic ejection variation are analyzed. The test results show that with the increasing temperature, the time interval between particle ejection and final overall ejection declines. 300℃ is the threshold temperature for the strength of granite treated by different temperatures under true triaxial condition with one single face. Below this temperature, the peak strength changes slightly and the brittleness increases with the increasing temperature. Beyond the temperature, the peak strength declines apparently and the brittleness decreases with the increasing temperature. At the compaction stage, the acoustic emission hits number of rock specimens increases with the increasing temperature. The time of “quiet period”, caused by the acoustic emission impact number decreasing apparently before rockburst, declines with the increasing temperature ranging from 300℃ to 700℃. The rockburst kinetic energy of specimens under temperatures of 25℃~300℃ increases with the increasing temperature, and that of specimens after temperatures of 300℃ to 700℃ decreases with the increasing temperature.