浅埋大跨度隧道的合理施工工法

Reasonable Method for the Construction of Shallow-depth and Wide-span Tunnel

采用平面弹塑性有限单元法研究浅埋大跨度隧道的合理施工工法。以实际施工中拟定的双侧壁导坑加拱部跳挖法为基础,采用开挖分步相同、开挖顺序不同的三种施工工法。工法一和工法二均先开挖左侧壁导坑,再开挖右侧壁导坑,工法一先开挖两边,再开挖中间,工法二先开挖中间,再开挖两边;工法三的左、右两侧导坑同时开挖,拱部土体先开挖中间、再开挖两边。对三种施工工法产生的地面沉降、洞周塑性区及洞周变形通过有限元数值模拟对比分析,认为工法三最为不利,工法一是最优的。但考虑现有施工条件工法二为实际施工过程中拟采用的工法,该工法引起的地面沉降最大值可控制在30mm以内,满足沉降控制及对周围环境保护的要求。研究认为:若地面有建筑物需要保护,应先开挖邻近建筑物一侧的导坑,拱部也应先开挖邻近建筑物一侧的土体。

Through 2D elasticity-plasticity FEM method, the reasonable construction method of the shallowdepth and wide-span tunnel is analyzed in this paper. Based on the construction method being used in practice,the paper prolmses three construction methods of the same divided blocks but different procedures： the first and second methods do not excavate left and right pilot tunnels at the same time, while the third method does. On the contrary of the first method, the center block of tunnel＇s roof is excavated earlier in the second and third method. Meanwhile this paper compares the surface settlement, the plastic region and the deformation around the tunnel of three different construction methods and presented the optimum construction method. By means of study, it is found that, if protection is necessary for ground building, the suggestion that the pilot tunnel and the soil of the tunnel＇s roof should be excavated first near the buildings which need protection is given.