浅埋超大跨四线高铁隧道开挖力学特性研究

以新建杭绍台高铁下北山隧道为工程依托，该隧道为浅埋超大跨四线高铁路隧道，基于现场取样进行室内岩石力学试验，合理确定了不同围岩等级的力学参数，在此基础上建立三维计算模型，分析浅埋超大跨隧道采用开挖工法时的力学特性。结果表明:双侧壁导坑法在围岩位移控制方面优于三台阶法，双侧壁导坑法中上导洞加临时钢支撑的措施能有效控制位移的变化速率，优于中上导洞一次开挖的做法，设计中应注意控制拱部导洞的开挖面积；在初支结构内力控制方面，双侧壁导坑中上导洞加钢支撑的方法初支结构的拉应力最小，结构受力最为安全。

Study on excavation characteristic of shallow-buried super-span four-line high-speed railway tunnel

Based on the new Hangshaotai high-speed railway Xiabeishan tunnel，which is a shallow-buried，super-long-span，four-line high-speed railway tunnel，indoor rock mechanics tests are carried out on the basis of field sampling，and the mechanical parameters of different surrounding rock grades are reasonably determined，on this basis，a three-dimensional numerical calculation model is established，and the excavation method of shallow-buried and super-long-span tunnel is analyzed.The results show that the displacement control of surrounding rock by the double-sided guide tunnel method is better than that by the three-step method.The measure of adding temporary steel support to the upper guide tunnel in the double-sided guide tunnel method can effectively control the change rate of displacement，which is superior to the one-time excavation of the middle and upper guide tunnel.In the design，attention should be paid to controlling the excavation area of the arch guide tunnel；in the internal force control of the initial support structure，the steel support should be added to the upper guide tunnel in the double-sided guide tunnel.The method has the least tensile stress and the safest structural stress.