隧道开挖对近邻复合桩基的影响效应

Influence of tunneling on neighboring loaded composite pile foundation

为了分析隧道开挖产生的位移场对近邻既有桩基的影响,本文基于给定的地层损失比并通过隧道上覆土层厚度与隧道直径之比来确定隧道收敛中心点的位置,给出了用位移控制有限元法模拟隧道开挖对近邻桩基影响的位移模式。与其他算法的结果比较表明,在地层损失比不大于3%的情况下,可以给出比较满意的结果。结合郑州地区工程地质条件和盾构隧道实际情况,用位移控制有限元法分析了隧道开挖对复合桩基承载性状的影响。结果表明,地层损失比和隧道与桩之间的水平距离是隧道施工对近邻桩基承载性状的主要影响因素。当隧道与桩之间的净距小于隧道直径时,施工中应采取一定的技术措施,以避免隧道开挖对桩基产生较大的影响。

In order to analyze the influence of displacement field generated by tunneling on adjacent pile foun-dation,a method of evaluating the tunnel boundary displacement is developed for predict the effects of tunnel excavation on adjacent pile foundation by the displacement controlled finite element method（DCFEM）. It is based on the given ratio of ground volume loss and a point of convergence of displacement vectors for soil around the tunnel boundary which is estimated using a ratio of the thickness of soil cover above tunnel and ex-cavated diameter. By compareing with the other methods,the results indicate that DCFEM can be effectively performed when a ratio of ground volume loss is less than 3%. Otherwise,the error is not negligible. The ef-fects of shield tunnelling of Zhengzhou on adjacent pile foundation are analyzed. It is shown that the ratio of ground volume loss and the horizontal distance between tunnel and pile foundation are the main influence fac-tors on the piles response. When the net distance between tunnel and pile is less than the diameter of tunnle, the measures should be taken to avoid affecting piles greatly.