断裂破碎带围岩松动区隧洞开挖应力变形特性分析

Analysis on Stress and Deformation Characteristics of Tunnel Excavation in Loosing Area of Surrounding Rock in Fault Zone

隧洞开挖过程中穿越断裂破碎带时,由于岩体条件差,在施工方式扰动下普遍会引起围岩出现松动圈,甚至坍塌。为厘清隧洞开挖过程中围岩松动圈应力及变形变化规律,以哈密抽水蓄能电站通风兼安全洞为例,建立三维数值计算模型,采用有限差分法,分析了断裂破碎带围岩松动圈隧洞开挖支护过程中围岩径向应力、变形及塑性区变化规律。结果显示顶拱径向应力主要集中在松动圈前端,且下半层的开挖对其应力影响较小;隧洞上、下半层开挖对拱顶径向变形规律一致,均沿开挖深度呈抛物线型分布,且最大值均位于松动圈前端;开挖完成后,不同部位围岩的变形大小关系为拱顶>边墙中心>拱肩;围岩塑性区主要分布在边墙和底板周围,且均为剪切塑性破坏,因此施工过程中还需加强边墙和底板处的支护措施。研究成果可为断裂带围岩坍塌形成松动圈隧洞支护设计提供参考。

Due to poor conditions of surrounding rock, it will often form loose area or even collapse in the excavation process of tunnel crossing fault zone. In order to explore the stress and deformation variation of surrounding rock with loosing area during tunnel excavation, the ventilation and safety tunnel of Hami Pumped Storage Power Station was taken as an example. And a 3 D numerical calculation model was established and finite difference method was adopted to analyze the variation law of radial stress, deformation and plastic zone during the excavation and support process of surrounding rock with loosing area in fault zone. The calculation results indicate that the radial stress of the top arch is mainly concentrated in the front of the loose area, and the excavation of the lower half layers has little influence on the radial stress of the top arch. The radial deformation of the upper and lower half layers of the tunnel is consistent with that of the arch, which is distributed in a parabolic shape along the excavation depth, and the maximum value is located at the front of the loosing circle. After excavation, the relationship of deformation value at different position on the monitored section is vault>center of side wall>arch shoulder. The plastic zone of surrounding rock is mainly distributed around the side wall and the bottom plate, and both of them are shear plastic failure. Therefore, the supporting measures at the side wall and bottom plate should be strengthened in the construction process. This study can provide reasonable suggestions for the support design of loose area tunnel formed by collapse of surrounding rock in fault zone.