软土深基坑分区开挖顺序对支护桩及城轨隧道影响的数值分析

Numerical alanalysis of the influence of district excavation sequence of deep foundation pit in soft soil on retaining piles and urban rail tunnels

为研究软土地区深基坑分区开挖及其施工顺序对自身和邻近城轨隧道的影响,以珠海某基坑工程为背景,运用有限元软件建立该工程的三维数值模型并模拟其施工过程,分析了基坑开挖方式和开挖顺序对基坑支护桩和邻近隧道的影响。结果表明:对于超大深基坑,分区开挖施工相比于整体开挖更好地利用了时空效应,有效控制基坑变形和减小对邻近隧道的影响;在分区方式相同的前提下,采用不同开挖顺序也会改变基坑的卸荷路径,最终导致同一基坑产生不同的隧道变形特性。由此得出,针对软土深基坑在施工方法上不仅要采用大化小的分区开挖方式,而且还应优先选择开挖释放量大的区域并搭配合理的支护加固方式,从而减少对基坑和邻近隧道的影响。

In order to study the influence of excavation and construction sequence of deep foundation pit on itself and adjacent urban rail tunnels in soft soil area,a three-dimensional numerical model of the project was constructed by using finite element software and the construction process was simulated with the background of a foundation pit project in Zhuhai,and the influence of excavation method and different excavation sequence on the foundation pit retaining piles and adjacent tunnel was analyzed.The analysis results showed that for the large deep foundation pit,the district excavation construction made better use of the space-time effect than the overall excavation,effectively controlling the deformation of the foundation pit and reducing the influence on the adjacent tunnel;at the same time,under the premise of the same partition mode,different construction sequences would also change the unloading path of the foundation pit,which would eventually lead to different tunnel deformation characteristics of the same foundation pit.It was concluded that the construction method of deep foundation pit in soft soil should not only adopt the method of converting large area of foundation pit into small area of sub-area excavation,but also give priority to selecting large area of excavation and matching reasonable support and reinforcement methods to reduce the impact on foundation pit and adjacent tunnels.