导洞隔离桩墙结构对浅埋暗挖隧道周边地层移动的限制作用

以北京城市铁路某浅埋暗挖区间隧道工程为例，分析了导洞隔离桩墙结构对中洞法双连拱隧道施工变形影响的限制作用。由于地面环境的制约，该工程在隧道侧上方开挖了两个小断面导洞，采用喷混凝土衬砌，并在导洞内向下施作钢筋混凝土排桩，以隔离隧道施工对附近两座高层建筑的不良影响。在分析导洞隔离桩墙工作机理的基础上，提出了一种解析解来估算隔离结构及附近地层的变形情况，并对施工过程的变形影响进行了三维有限元模拟。把解析解和有限元计算结果与施工监测数据进行了比较，总结了影响隔离结构作用效果的关键因素。

Constraint Effect of Pilot-Drift and Separation-Pile Structure on Ground Movements Induced by Shallow Tunneling

Based on the construction of a shallow-buried tunnel in Beijing metro,the constraint effect of pilot-drift and separation-pile structure on ground movements induced by shallow tunneling is analysed. Restricted by the surface environment of construction area,two pilot-drifts with small cross-section and shotcrete linings were constructed above each side of the subway running tunnel,and reinforced concrete piles were installed in the ground below the drifts to separate the negative effects of tunnel construction on the two high-rise buildings located nearby at each side of the tunnel,respectively. Based on the mechanisms of the pilot-drift and separation-pile structure,a simplified analytical model is formulated to estimate the deformation of structure and ground,and a three-dimensional elasto-plastic finite element model is constructed to simulate the tunneling sequence and its effects on surrounding environment. The comparison between the modeling results and in-situ monitoring data is conducted,and the key factors affecting the performance of the pilot-drift and separation-pile structure are summarized.