多条盾构隧道穿越既有桥基的三维有限元分析

3-D Finite Element Analyses of Shield Tunneling Passing Pile Foundation of Existing Bridges

城市建设和地下轨道交通的飞速发展给地铁施工带来了全新的挑战,施工环境的日益复杂多变使得城市地铁施工难度不断加大.结合天津某地铁线路工程实例,利用三维有限元软件PLAXIS 3D2012分析了四线同时穿越既有桥基时,盾构穿越对桥基变形受力性状的影响及对周边环境土体变形的影响.计算结果显示:隧道掘进可引起桩基础产生上部沉降、下部隆起的变形,以及较小的水平位移;四线盾构掘进后,土体产生的累积沉降形状为"U"型;四线穿越后的桥基群桩的桩侧总摩阻力基本不变;计算得到的相应控制指标均处在变形控制标准以内,工程安全可行.

With new challenges brought by the rapid development of urban construction and subway construction,metro construction has become increasingly difficult due to the complex construction environment.Based on a case history of Tianjin Metro Line,the influence of a 4-line shield tunneling through the pile foundation of an existing bridge on the stress and the deformation of piles and the surrounding soil were studied using three-dimensional finite element models via PLAXIS 3D2012.It has been shown that the shield tunneling can cause a settlement of pile head,an uplift of the pile bottom,and a small horizontal displacement of piles.A U-shape trough of soil surrounding the pile foundation has occurred after the 4-line shield tunneling.The total shaft resistance of each pile almost remains unchanged after the 4-line shield tunneling.The project is regarded to be safe since each calculated parameter meets the requirement of control standards.