三维隐伏溶洞对临近隧道围岩破坏特征的影响

Influence of 3D cavern on the failure characteristics of adjacent tunnel

针对贵州紫金部分矿井巷道围岩存在溶洞经常导致地下工程围岩呈现不稳定状态或剧烈破坏现象这一典型工况,利用简化的类岩石试样开展真三轴压缩试验,结合声发射和内窥摄像头监测围岩的变形和次生破坏行为.研究表明:1)溶洞将导致试样z轴峰值荷载降低约25%,次生破坏的出现时间更早,且主导性破坏更加集中地出现在峰值应力时段. 2)位于隧道右上侧的溶洞导致隧道右侧围岩呈现一种新的板状破坏,即破坏由隧道-溶洞的中间岩柱起始、沿隧道右侧壁表层围岩纵向发展、并最终形成岩块向内移动,该类型破坏的起始位置和岩块厚度与典型板裂破坏明显不同. 3)压缩型应力和剪切破坏在隧道围岩的板裂破坏过程中占据主导地位,且由于三维溶洞位于隧道右上方,其对隧道下方和左侧围岩的影响相对较小. 4)球形溶洞导致其与隧道之间的岩体内出现更为密集的次生拉伸和剪切裂纹,即该区域内岩体破坏程度明显高于其他位置.

To address the special condition of cavities in the tunnel surrounding rock in Guizhou Zijin golden mine(caves in geological bodies often lead to unstable and even violent damage of underground engineering rock enclosures),the deformation and secondary damage behavior of the surrounding rock were monitored by acoustic emission and tunnel endoscope cameras based on true triaxial compression tests of simplified rock specimens containing tunnels and cavities.The study shows that the prefabrica-ted cavern leads to a 25%decrease of z-axis peak stress of samples,the secondary failure shows earlier appearance time,and the dominant secondary failure concentrates during the final peak stress period.Prefabricated cavern located on the right top side of the tunnel contributes to a new type of splitting failure,which starts in the middle rock between the tunnel and cavern,develops vertically along the surface field of the tunnel sidewall,finally forms a divided rock plate and move inwards;the above characteristics are different from that of the traditional splitting failure.The compressive force and the corresponding shear failure play the dominant role in the construction of splitting failure;the prefabri-cated cavern shows a slight influence on the bottom and left surrounding rocks of the tunnel because of the location(right-top outside the tunnel).The prefabricated cavern contributed to the dense distribu-tion of secondary tensile and shear cracks in the rock between the tunnel and cavern,and the corre-sponding destruction level of this region is relatively higher than rock at other positions.