基坑开挖对既有地铁隧道及地表变形影响分析

Analysis of influence of excavation of foundation pit on existing subway tunnel and surface deformation

基坑开挖会造成下部隧道周围土压力变化以及土体产生位移,使隧道结构稳定性受到影响,从而变形控制显得尤为重要。以合肥南站南广场基坑工程实测数据为例,采用PLAXIS 2D有限元软件对基坑下部隧道和地表变形的情况进行数值计算。研究表明:数值计算结果与实测值较为吻合,隧道发生竖向和水平位移,竖向位移比水平位移大,隧道的位移值随着开挖深度呈线性趋势;基坑开挖会引起隧道上方地表变形,地表沉降呈向下二次抛物线形式,坑底产生了塑性隆起。

The excavation of the foundation pit may cause the earth pressure change around the nearby tunnel and the displacement of the soil body, and affectthe stability of the tunnel structure, so its deformation control is particularly important. As an example of the measured data of the foundation pit of the South Square of Hefei South Station, the PLAXIS 2 D finite element software is used to numerically calculate the tunnel and surface deformation of the foundation pit. The results show that the numerical calculation results are in good agreement with the measured values, and the vertical and horizontal displacements occur in the tunnel, and the vertical displacement is larger than the horizontal displacement. The displacement value of the tunnel has a linear trend with the excavation depth. The excavation of the foundation pit can cause the surface above the tunnel. Deformation, the surface settlement is in the form of a downward quadratic parabola, and a plastic bulge is generated at the bottom of the pit.