软弱相间水平层状岩体隧道围岩变形特征分析

Characteristic Analysis About the Surrounding Rock Deformation in Tunnel with Weak and Inter-bedded Strata

为研究软弱相间水平层状岩体隧道围岩变形破坏机理并正确指导设计施工,采用现场隧道围岩松动圈测试并结合三维离散元数值模拟方法对不同工况下隧道塑性区分布、收敛位移进行比较分析验证。结果表明:隧道墙脚容易产生塑性变形,造成底部岩体支撑方式发生变化,由于岩体软弱相间且层间连接弱,在拱顶沉降与两侧围岩水平收敛产生的水平力作用下,导致底部岩体发生向上的变形破坏。针对其变形破坏机理,对其支护措施进行研究,发现对底部岩体进行锚杆加固,增大了层间岩体连接,减小了各向异性,提高了岩体的整体强度,有效降低隧道底部岩体向上变形程度,防止隧道底部隆起,保证施工和运营安全。

The paper studies the deformation and failure mechanism about the surrounding bedded rock mass in the tunnel with weak and inter-bedded strata, and makes a guidance for designing and construction accurately. Distribution of tunnel plastic zone and convergence displacement under different conditions are analyzed and compared by adopting threedimensional discrete element method, with testing the loose circle of tunnel surrounding rock. The results show that there is a lot of chance that plastic deformation happened in the corner of the tunnel which changes the supporting method of rock mass at the bottom. Because of the weakness of rock mass alternating with each other and the connection of inter-layer, the upward deformation of bottom rock mass is occurred under the action of the horizontal force caused by the settlement of vault and convergence of surrounding rock. According to the deformation and failure mechanism, supporting measures are studied. The anchor rod towards bottom rock mass are reinforced, the connection of inter-layer rock mass is increased and the strength of the monolithic rock mass is improved, so that the upward deformation of the rock mass about the bottom of the tunnel is effectively reduced, which can also prevent bottom from uplifting and ensure the safety of construction and operation of the tunnel.