怀邵衡铁路某岩溶大断面隧道围岩软弱破碎，采用三步临时仰拱法开挖时，开挖过程中围岩容易发生大变形和失稳，因此选择合理的开挖施工参数非常重要。本文采用三维弹塑性有限元方法对不同循环进尺的岩溶隧道进行了模拟分析、台阶长度条件下施工时隧道围岩与支护变形特性，对比分析了不同开挖施工参数的优缺点，为隧道开挖施工参数选取提供了依据。研究结果表明，岩溶隧道V级围岩条件下选择开挖进尺2 m，台阶长度6 m开挖施工，虽然会导致施工速度有所降低、施工成本增加，但隧道变形可以明显控制，确保隧道施工安全。最后，通过现场实测数据验证了该方法的有效性。
The surrounding rock of a Karst tunnel of Huaishaoheng railway is soft and crushed, which uses three-step excavation method with temporary inverted arch and is easy to cause large deformation in surrounding rock and is not steady, so it’s very important to choose proper excavation construction parameters. Based on the Karst tunnel, it simulated deformation of surrounding rock and supported under different footage driving cycle and step length by using 3D elastic-plastic fi-nite element method, compared the advantages and disadvantages of each excavation construction parameter, and provided a basis for proper excavation construction parameters selection. The results show that the excavation of Karst tunnel under V level surrounding rock can reduce the construction speed and increase the construction cost using 2 m excavation driving cycle and 6m step length, but it can control the deformation obviously and ensure the construction safety. Effectiveness is verified by the measured data obtained at site.
