卸荷条件下岩爆机理的试验研究

岩体卸荷和加荷条件下的力学特性有本质区别，高地应力地区地下工程开挖过程中发生的岩爆是一种典型的开挖卸荷现象。对粉砂岩试样进行了保持轴向变形不变的卸围压试验，在试验结果分析研究的基础上，对卸荷导致的岩爆进行了研究。研究表明。处于三轴应力状态下的岩体，如果某一方向的应力突然降低造成的岩石在较低应力水平下破坏，那么原岩储存的弹性应变能会对外释放，释放的能量将转换为破裂岩块的动能，进而町能引起岩爆。采用提前钻孔释放能量的方法。将工作面前方围岩中的能量提前释放，在即将开挖的围岩四周形成一个低应力的保护壳，能够减缓或降低岩爆的发生。

STUDY ON THE EXPERIMENT OF ROCK BURST UNDER UNLOADING CONDITION

The behavior of rock deformation and its failure characteristics under loading and unloading conditions are substantially different. Rock burst during excavation of underground engineering in areas of high geostress is a typical failure phenomenon due to unloading. Triaxial unloading tests are conducted in this paper. Rock specimens are firstly compressed in a triaxial cell and then the confining pressure is reduced progressively while keeping the axial deformation constant. Experiment results show that specimens absorb energy during axial compression loading and release energy during failure at confining reduction. Strain energy stored in rock is sufficiently large to cause failure when it is released. To prevent rock burst, one of the basic methods is to release the strain energy in rock before excavation. Pre-boring has been successfully used to release the strain energy and to prevent the rock burst in mines. Rock burst could also be controlled or released by adjusting the speed of excavation.