既有桥桩对盾构引起地表沉降槽的变形影响

Influence of existing bridge pile foundation on the deformation of surface settlement trough induced by shield tunneling

针对预测盾构开挖引起的地表沉降槽变形曲线,通常采用Peck公式或其修正公式,但该公式没有考虑邻近桥桩刚度对地表沉降槽变形的影响。采用Midas GTS NX建立三维有限元模型,分析不同桩径和桩-隧道间距对地表沉降槽曲线的影响,提出一种适用于预测盾构近距离侧穿桥桩时地表沉降槽的偏态分布曲线。以长沙地铁5号线圭塘站至高桥南站区间为工程背景,将有限元计算结果和现场实测值与偏态分布曲线值进行对比分析。研究结果表明:当L/D<1.8时,地表沉降槽变形曲线会呈现明显偏态分布,整体地表变形会在桩基附近出现“绕桩”现象。采用偏态分布曲线可以较好地预测邻近桥桩影响下盾构开挖引起的地表沉降槽变形,可为此类工况修建盾构隧道提供参考。

Peck formula and its modified formulas are usually used to predict the deformation curve of surface settlement trough induced by shield tunneling without considering the effects of stiffness of existing adjacent bridge pile. Three-dimensional finite element models were established by Midas GTS NX to analyze the effects of different pile diameters and different distances between pile and tunnel on the surface settlement trough curve,and a kind of skewed distribution curve of the surface settlement trough was proposed,which is suitable to predict the surface settlement trough curve when shield tunneling passes through the bridge pile at a short distance. Based on the engineering background of the shield tunneling line between Guitang station and Gaoqiao South station of Changsha No. 5 Metro Line,the results of finite element simulation and in-situ measurement were compared with the skewed distribution curve. The results show that when L/D<1.8,the deformation curve of surface settlement trough presents an obvious skewed distribution,and the overall surface deformation appears‘around pile’phenomenon near the pile foundation. The skewed distribution curve can be used to predict the surface settlement trough induced by shield tunneling under the influence of adjacent bridge piles,which provides a reference for the construction of shield tunnel under similar conditions.