岩溶大断面隧道开挖支护方案比选分析

Comparison of Support Options for Karst Tunnels with a Large Section

怀邵衡铁路某大断面隧道穿越岩溶破碎带,开挖过程中围岩易产生大变形,甚至出现涌泥涌砂现象,因此选择合理的开挖支护方案显得尤为重要。文章针对该岩溶隧道,采用荷载-结构法的二维有限元模型,分析了隧道采用不同支护方案(两道横向支撑与竖向支撑,仅有两道横向支撑,无内支撑)在不同的荷载释放比例下隧道初期支护的变形与受力特性,对比分析了不同开挖支护方案的优缺点,为选择合理的岩溶隧道开挖支护方案提供参考。研究结果表明:岩溶隧道选择无内支撑支护方案开挖施工,易导致围岩变形和初期支护内力较大,但仍在安全范围以内,可以在保证隧道施工安全的前提下,确保施工进度。最后,现场实测数据验证了该支护方案的有效性。

A large section tunnel on Huaishaoheng railway passes through Karst fracture zone,which is easy to cause large rock deformation,and even mud and sand gushing,so it’s important to choose a proper excavation support option.Based on the Karst tunnel,it simulated deformation and stress under different support options(two horizontal support and a vertical support;two horizontal support only,no internal support)and different load release proportions by using 2 D load-structure method,compared the advantages and disadvantages of each support option,and provided a basis for proper selection of support option.The results show that the excavation of Karst tunnel with no internal support can easily cause large rock deformation and large internal force of initial support,but they are within the safety range and can ensure the construction progress under the premise of safety construction.Effectiveness is verified by the measured data obtained at site.