浅埋大跨暗挖地铁车站施工地表沉降分析

Analysis of the Surface Subsidence during the Excavating of Large- span Subway Station under Shallow Cover

研究目的：针对浅埋大跨暗挖隧道地铁车站施工中,易产生地层的反复扰动、力学转换复杂等现象,引起地表过大沉降。本文主要介绍浅埋大跨暗挖地铁车站施工,通过对地表沉降的监控量测,分析变形规律,并对各种影响效应进行分析。研究结论：通过研究得出以下结论：（1）车站主体施工引起的地表沉降累计沉降平均为-36.31 mm,应该对地表沉降的限值进行修正,达到施工对周边环境影响最小,同时降低工程成本;（2）车站主体施工引起的地表沉降槽为：以车站中线为中心,拐点距沉降槽中心18 m左右,车站中线20 m以外地表沉降开始迅速减小,沉降分布范围为车站中心左右两侧约25~30 m;（3）车站主体施工引起的地表沉降主要发生在小导洞开挖支护和扣拱施工阶段,其地表沉降分别占到总沉降的48.47%和93.03%,尤其是小导洞开挖支护阶段,对地表沉降的贡献接近总沉降的一半;（4）该研究成果可为类似浅埋大跨暗挖地铁工程的设计、施工提供借鉴。

Research purposes： During the excavating of large -span subway station with shallow cover, the phenomenons such as repeated disturbance, complex mechanical conversion easily occur, which bring excessive surface subsidence. In the paper, the construction of tunnel arch excavation and support with shallow cover is introduced mainly, the analysis of deformation law, and influences of construction sequence are made on basis of monitoring and measurement for the surface subsidence. Research conclusions： The research conclusions show： （1） The average value of surface subsidence is up to -36.31 ram, the limit of the surface settlement should be modified in order to decrease both negative effect on the surrounding environment and construction cost. （2） The ground surface settlement trough due to the construction is at the center of subway station, the distance between flex point and the center of subway station is about 18 m, meanwhile, the surface subsidence over 20 m from the center of subway station decreases rapidly, the distribution of the surface subsidence is 25 -30 m from both sides of the subway station. （3） The surface subsidence due to construction of the subway station mainly occurs in a small pilot tunnel excavation supporting and buckle arch construction stage, 48.47% and 93.03 % of the total settlement, especially during the course of a small pilot tunnel excavation supporting, which is close to half of the total settlement. （4） The result can provide the reference for design and construction of the similar engineering.