高温后花岗岩岩爆的真三轴试验研究

True triaxial tests on rockburst of granite after high temperatures

利用自主研发的真三轴岩爆试验系统,以200℃~700℃不同高温冷却后和常温25℃下的红色粗晶花岗岩作为岩样,进行岩爆弹射破坏过程模拟物理的试验。在借助高速摄像系统和声发射系统监测岩爆过程的基础上,分析了不同高温作用后岩样的岩爆弹射过程、破坏形态特征、峰值强度、声发射特性、碎块特征以及弹射动能的变化规律。研究结果表明：随着温度的升高,岩样从出现小颗粒弹射到整体弹射破坏的时间间隔逐渐减少;300℃为该类花岗岩高温后单面临空真三轴强度的阀值温度,小于等于300℃时,岩样的峰值强度变化不大,岩样脆性随温度的升高而增大,大于300℃时,岩样的峰值强度呈明显下降趋势,岩样的脆性随温度升高而降低;在岩样压密阶段,声发射撞击数随温度升高而增大,大于300℃时,岩爆发生前夕声发射撞击数显著下降的“平静期”持续时间随温度升高呈增大趋势;25℃-300℃温度范围内,岩爆弹射动能随温度升高明显增大,300℃-700℃高温后,岩爆弹射动能随温度升高显著减小。

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＂C 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 fi＇om 300~C to 700＂C. The roekburst 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.