双线盾构施工对基坑底板沉降及内力的数值分析

上海地铁10号线同济大学站一国权路站双线盾构长距离平行穿越下立交深基坑，穿越距离为630m，隧道与下立交基坑围护净距约2．0m，与下立交底板底的距离为6．1～9．3m，施工现场环境复杂，盾构施工可能导致下立交深基坑底板发生竖向位移并产生附加内力。本文采用三维数值方法，模拟分析在基坑底板浇筑完成的情况下，盾构施工对基坑底板沉降及内力的影响。分析表明：随着围护结构深度的增加，底板横轴绝对沉降量和相对沉降量均逐渐减小，底板纵轴沉降量逐渐减小，基坑底板横轴弯矩逐渐增大，基坑底板纵轴弯矩变化值基本一致；随着盾构的推进，基坑底板先下部受拉、上部受压，随着同步注浆的进行，基坑底板下部受压、上部受拉。数值计算较好地指导了实际工程的施工。

Numerical analysis on settlement and internal force of foundation pit bottom board caused by the construction of double-tube shields with long-distance passing under deep foundation bottom

The construction of the double-tube shield tunnel from Tongji University Station to Guoquan Road Station of Shanghai Subway Line 10 is complex, which passed the long-distance paralleled through the bottom of the under crossing foundation finally caused the lateral displacement of the foundation pit support, the passed distance is about 630m, the distance between the tunnel and the diaphragm wall is about 2.0m, the distance between the tunnel and the bottom board is about 6.1 -9.3m. By making use of three-dimensional finite element analysis, the effect of the settlement and internal force of the bottom board are analyzed on the conditions of the construction finish of the bottom board. The analysis shows that ： with the increase of the depth of the foundation pit support, the absolute and the relative settlement of the transverse axis are decreasing, the settlement of the longitudinal medial axis is decreasing too ; the moment of the transverse axis is increasing gradually, the change values of the moments are basically identical; with the shield driving, the low part of the bottom board is subjected to the tension firstly, the top part of the board is compressed; however, with the synchronized grouting driving, the low part of the bottom board is subjected to the pressure, and the top part of the board is subjected to tension. The numerical analysis results provide the very good guidance to the project construction.