基坑开挖对临近基坑地铁高架结构变形的影响

以苏南地区临近城市轨道交通结构的基坑工程为例,通过三维有限元模拟施工过程,反演适宜模拟该基坑施工过程的计算参数,并在此基础上研究不同开挖距离、基坑规模、开挖深度、基坑数量和施工工序的基坑施工对临近地铁高架结构的影响。结果表明:基坑与结构水平间距小于2H(H为基坑深度)时,结构横向变形发展大于竖向,水平间距为1H时,桥墩水平位移和沉降达到最大;地铁高架桥桥墩附加变形伴随着基坑宽度的增大而迅速增大,当基坑宽度大于8H时,影响迅速减小;基坑开挖深度对基坑中线4 H范围内的桥墩影响最大,尤其是开挖深度超过10m后;多个基坑施工引起的结构变形表现出明显的非线性叠加效应;多基坑施工工序对结构总变形略有影响。

Influence of foundation pit excavation on the deformation of adjacent subway elevated structure

Taking a foundation pit near the urban rail transit structure in southern Jiangsu as an example, the soil parameters were obtained by inverse analysis and three-dimensional finite element method simulations. On this basis, the influence of different excavation distances, excavation qeometries, number of foundation pits and construction procedure on the deformation of adjacent subway elevated structure is studied. The results show that, when the horizontal distance between foundation pit and structure is less than 2H (H represents the depth of the foundation pit), the lateral deformation of the structure is larger than that of vertical. The horizontal displacement and settlement of elevated bridge pier reach the maximum when horizontal distance is 1H. Besides, the additional deformation of subway viaduct piers increases rapidly with width of foundation pit. It decreases significantly when the width of foundation pit is larger than 8H. The depth of excavation of the foundation pit has the greatest influence on viaduct pier within 4H range of the central line of the foundation pit, especially when the excavation depth is more than 10 m. It is found that the structural deformation caused by multiple foundation pit construction shows obvious nonlinear superposition effect, while the construction procedure of multiple foundation pit has a slight influence on the total deformation of the structure.