圆形隧洞爆破荷载与瞬态卸荷作用围岩应变能效应研究

Strain energy characteristics of surrounding rock under blasting load and transient release of geostress during excavation of circular tunnel

深部岩体开挖过程中,能量的释放与耗散是导致围岩发生损伤破坏的重要诱因。针对深埋圆形隧洞爆破开挖,采用理论模型研究微差段间爆破荷载与地应力瞬态卸荷重复扰动及耦合作用下围岩应变能的变化规律,并基于弹性应变能判别准则计算围岩损伤范围。研究结果表明:在爆破荷载作用下,围岩应变能经历了先增大再减小最终趋于稳定的动态变化过程;在地应力的瞬态卸荷作用下,围岩应变能经历了先减小再增大最终趋于稳定的过程;二者耦合作用会进一步加剧围岩应变能动态调整过程,并且体现出更加明显的微差段间重复扰动效应,以开挖轮廓附近起爆的两圈崩落孔及周边孔最为明显。爆破荷载主要引起围岩张拉破坏,而地应力瞬态卸荷主要导致围岩压剪破坏,在二者耦合作用下地应力的存在会抑制爆破荷载引起的围岩张拉破坏,从而减小围岩的损伤范围。最后,采用锦屏二级水电站引水隧洞实测围岩损伤范围对理论计算方法的正确性进行了验证。

During the excavation of deep tunnel in rock mass, the energy release and dissipation are the important factors which lead to the damage of surrounding rock. The blasting excavation of deep circular tunnel was studied theoretically to investigate the variation of strain energy in surrounding rock under the blasting load with multi-micro-second delays, the repeated disturbance of transient release of geostress, and the coupling effect of these two dynamic loads. The damage range was calculated based on the elastic strain energy criterion. Results show that the strain energy in surrounding rock under the blasting load increases firstly, then decreases and stabilizes finally. The strain energy under the transient release of geostress decreases firstly, then increases and stabilizes finally. The dynamic adjustment of strain energy is greatly influenced by the coupled effect of blasting and geostress release. This effect is reflected most obviously in the two rings of stope holes and a ring holes near the excavation boundary. The blasting load causes mainly the tensile failure of the surrounding rock, while the transient release of geostress results mainly in the compression-shear failure. The existence of the geostress restrains the damage caused by blasting and reduces the damage range of surrounding rock. At last, the correctness of the theoretical method is verified by the measured damage range of diversion tunnels in Jinping II hydropower project.