大跨度浅埋软弱围岩隧道施工工法比较

针对大跨度浅埋软弱围岩隧道施工问题,分析了双侧壁导坑法和微台阶留核心土法的技术特点和适用条件,双侧壁导坑法施工在控制围岩变形及地面沉降方面优于三台阶法,且产生的围岩塑性区较小,微台阶留核心土法在施工进度、资源利用、造价、工序转化及施工难度方面具有优势。结合工程实例,证实仅在围岩具有自稳能力并且可以机械开挖时,可以优先采用微台阶留核心土法,其它条件下宜采用双侧壁导坑法。

Comparison of Construction Methods for Large-span Shallow Weak-rock Tunnel

Analyses are made of the technical characteristics and application conditions of dual sidewall drift method and micro-steps with remaining core soil method for large-span shallow weak-rock tunnel construction.The dual sidewall drift method is better than the three-step method in the control of the surrounding rock deformation and land subsidence and produces smaller plastic zone.Micro-steps method has its advantage in construction schedule,resource utilization,cost,process transition,and the difficulty of construction.With an example,it is confirmed that priority can be given to the use of micro-steps with remaining core soil only when the surrounding rock has a homeostatic capacity and mechanical excavation is feasible.The dual sidewall drift method should be used under other conditions.