True Triaxial Experimental Study On Rockburst Of Granite After High Temperatures

Rockburst is a geological hazard phenomenon caused by the sudden release of rock elastic energycaused by the artificial excavation and external disturbance of the rock under the condition of high stress, which is a complex dynamic disaster. The occurrence of rockburst can result in the death of the personnel, the destruction of the equipment and the delay of the construction period, causing great economic losses. The ejection process of rockburst of coarse-grain granite treated with different high temperature is studied based on self-developed ture triaxial rockburst test system. Based on monitoring ejection process of rockburst with high speed system and acoustic emission system, the ejection process of rockburst, damage morphology, peak stress, acoustic emission characteristics, fragments feature and kinetic ejection variation are analyzed. The main conclusions are as follows:(1)After high temperature, the failure characteristics of the granite specimens changed significantly with the temperature of the specimen change. With the increase of temperature of the specimen, the interval from the emergence of small particles to the whole ejection failure is gradually reduced.300℃ is a threshold temperature for the strength of granite ireated with different temperatures under condition of true triaxiai with one single face. Below that temperature, the peak-strength changed slightly and the brittleness increases with the increasing temperature. Beyond that temperature, the peak-strength declines apparently and the brittleness decreases with the temperature increasing. With the increase of the maximum temperature, the breaking degree of the rock burst is increased. In the near rock burst, the impact decline sharply, there will be a period of quiet", The time of "quiet period" of acoustic emission impact number decreasing apparently before rockburst, and increase with the temperature increasing ranging from 300℃ to 700℃.(2)The energy accumulation, dissipation and release process of granite specimen after different temperature change remarkably with temperature increase, the pre-peak elastic strain energy of specimens increase with increasing temperature when heated from 25 ℃ to 300℃,and decrease when heated from after 300℃ to 700℃. the Pre-peak dissipated energy of specimens decrease with increasing temperature when heated from 25℃ to 300℃, and increase when heated from 300℃ to 700℃, the rockburst kinetic energy of specimens increase with increasing temperature when heated from 25℃ to 300℃, and decrease when heated 300℃ to 700℃.