竖井开挖的不稳定性和岩爆的力学机制

基于稳定性理论和弹塑性厚壁筒的解析解，研究了竖井开挖过程的平衡路径，并将屈服后的井壁压力--位移平衡路径曲线应用到围岩的稳定性分析.研究表明，竖井围岩的不稳定及其岩爆的发生不仅取决于岩石材料应力应变全过程曲线的峰后特性，还取决于竖井开挖过程对应的平衡路径曲线的类型.平衡路径曲线能够描述围岩结构加载屈服后的力学行为.平衡路径的曲线形状只可能有两种类型，一种曲线上的点都处于稳定的平衡状态，虽有塑性变形的累积，但不会失稳崩落；另一种曲线则发生极值点型井壁失稳并伴有位移突跳.竖井开挖过程的平衡路径曲线是判定围岩岩爆发生的关键因素.极值点型失稳和位移突跳是均质围岩中岩爆可能发生的一种力学机制. 

INSTABILITY OF SHAFT EXCAVATION AND MECHANISM OF ROCKBURST

On the basis of stability theory and the analytical solutions of thick-walled cylinder of elasto-plastic material, the post-yield equibrium path of shaft excavation is tracked and adopted to stability analysis of the surrounding rock. The results show that the instability of surrounding rock and the occurrence of rockburst depend not only on the post-peak property of stress-strain total curve of rock material, but also on the type of equilibrium path curves during excavation of shaft. The equilibrium path curve describes the post-yield behaviour of the structure of surrounding rock, and can only be classified into two types. A point on the curve of one type is corresponding to a stable stage of the equilibrium, which accumulates plastic deformation but the instability not occurs. The other type is related to limit-point-type instability and displacement snap-through. The equilibrium path curve of shaft excavation is a key factor of inducing rockbursts of surrounding rock. The limit-point-type instability and displacement snap-through are possible mechanism of rockbursts in homogeneous rock.