既有盾构隧道地层中基坑开挖方案对比分析

The Analysis about Pit Foundation Excavation Scheme of Existing Shield Tunnels Excavation Scheme

针对黄土地区三个平行基坑开挖对下伏既有盾构隧道影响,运用FLAC3D有限差分法数值软件,结合实际场地的水文地质和工程地质条件,建立三维数值模型,对比了三个基坑同时开挖与分步开挖引起的既有盾构隧道结构的隆起位移与应力.研究结果表明,基坑开挖对下伏既有盾构隧道隆起位移影响较大,基坑内结构施作后既有盾构隧道隆起位移减小,三个基坑分步开挖相对于同时开挖将减小对下伏既有盾构隧道的影响,并且三个基坑分步开挖引起盾构隧道结构内力满足强度要求,建议三个平行基坑开挖工法为先两侧后中间开挖施工.

According to the loess area of three parallel for shield tunnel affection,using FLAC3 Dfinite different numerical software,to combine with the hydrogeology and engineering geology conditions,establish the three-dimensional numerical model,and compare the uplift displacement of shield tunnel and stress for the three pit foundations to excavate by synchronization and distribution.The researching result that,the excavation of shield tunnel uplift displacement has a greater impact on the underlying,foundation pit structure after the application for existing shield tunnel uplift displacement decreases,the three foundation excavation by steps the excavation will reduce the influence both on the underlying shield tunnel,and the three foundation excavation by steps of internal force caused by shield tunnel structure to meet the strength requirements,recommend three parallel excavation method for the two sides first and then the middle excavation.