弱动力扰动对花岗岩圆形隧洞岩爆影响的试验研究

Experimental study on influence of weak dynamic disturbance on rockburst of granite in a circular tunnel

为探究弱动力扰动对岩爆的影响,利用高压伺服动真三轴试验机,对含预制圆形贯穿孔洞的红色中粗晶粒立方体花岗岩试样进行弱动力扰动荷载条件下的岩爆模型试验,模拟隧洞洞壁围岩的岩爆弹射破坏过程,并采用声发射系统和视频观测系统对其进行监测、记录。基于无扰动、高应力下开始施加扰动和低应力下开始施加扰动3种加载路径的试验数据,从岩爆弹射破坏、岩爆坑破坏形态、声发射信号特征及岩爆烈度4个方面,详细分析弱动力扰动条件下的岩爆特征。研究结果表明:弱动力扰动会降低洞壁围岩发生岩爆时所需要的应力水平,增大岩爆破坏发生的范围。高应力下开始施加的扰动荷载会促进最终岩爆快速发生;而在低应力下开始施加的扰动荷载,岩爆的发生过程较为缓慢。相比与静应力条件下的岩爆,高应力下开始施加扰动触发的岩爆更剧烈,低应力下开始施加扰动触发的岩爆剧烈程度较弱。这主要是因为在高应力下开始施加的扰动对能量释放起到了激发和放大的作用,低应力下开始施加的扰动对能量释放仅起到激发的作用。

In order to study the influence of weak dynamic disturbance on rockburst,test on cubic medium-coarse grained granite specimen with a circle hole was conducted to simulate the rockburst ejection process in circle tunnel subjected to weak dynamic disturbance.Three loading paths,namely,no disturbance,weak dynamic disturbance starting at high-stress level,and weak dynamic disturbance beginning at a low-stress level were considered.The testing process was recorded using AE and video monitoring system.The ejection failure process,characteristics of rockburst pit,acoustic emission signal characteristics and rockburst intensity were investigated.The testing results show that the weak dynamic disturbance can reduce the stress level at the occurrence of rockburst and increase the range of rockburst.The applied dynamic disturbance at a high-stress level leads to a rapid occurrence of rockburst.In contrast,when the weak dynamic disturbance is applied at a low-stress level,rockburst will occur in a gradual manner.In addition,compared with that without dynamic disturbance,rockburst with the weak dynamic disturbance starting at high-stress level has a higher intensity,while that with weak dynamic disturbance starting at low high-stress level has a lower intensity.This is because that weak dynamic disturbance starting at high-stress level is capable of stimulating and amplifying the energy release process,while weak dynamic disturbance starting at a low-stress level is only capable of stimulating the energy release process.