考虑开挖宽度的基坑卸荷引起下卧盾构隧道变形计算

Deformation calculation of underlying shield tunnel caused by unloading of foundation pit considering excavation width

计算基坑坑底隆起变形对下卧盾构隧道纵向变形的影响,建立基坑开挖引起的土体位移计算模型。引入转动与错台变形协调盾构隧道模型,基于影像源法,推导得到基坑开挖引起的下卧盾构隧道的纵向变形计算公式。结合3个实际工程监测数据,对比B-W,B-P法,验证计算方法的正确性,并对基坑坑底最大隆起量、基坑开挖宽度、开挖深度、隧道埋深这4个影响因素进行分析。研究表明:下卧隧道最大隆起值和基坑坑底最大隆起值呈正相关规律;随着基坑开挖宽度的增加,隧道隆起大小以及范围相应的增加;隧道埋深和下卧隧道隆起值呈非线性递减规律;减少基坑坑底隆起变形和隧道轴线方向基坑开挖宽度能有效控制下卧隧道纵向变形。

To calculate the influence of the uplift deformation of the foundation pit bottom on the longitudinal deformation of the underlying tunnel,the calculation model of foundation pit excavation deformation is established.A cooperative tunnel model of rotation and staggered platform deformation is adopted.Based on the virtual image technique,the formulas of longitudinal deformation of the underlying tunnel caused by the excavation of the foundation pit are derived.Three sets of typical cases were selected for calculation and analysis.The B-W and B-P methods are compared to verify the correctness of the calculation method.Moreover,the influence of four factors,namely the maximum uplift of the pit bottom,the excavation width and depth of the pit and the buried depth of the tunnel are analyzed.The results show that there is a positive correlation between the maximum uplift value of the foundation pit bottom and the maximum uplift value of the underlying tunnel.As the excavation width of the foundation pit increases,the uplift value and uplift range of the tunnel increase accordingly.The buried depth and the uplift value of the underlying tunnel show a nonlinear decreasing law.The longitudinal deformation of the underlying tunnel can be effectively controlled by reducing the uplift deformation of the pit bottom and the pit excavation width along the tunnel axis.