双线地铁开挖地表沉降预测及影响分析

Surface sedimentation prediction and impact analysis induced by the double line subway excavation

各大中小城市通过开展地下交通工程缓解地面交通压力,但地铁路线多选在已建的市政道路下,故而必然对既有管线带来影响。有些管线被迫迁徙,但由于客观条件当其无法迁徙时,必须采取合理的施工方案约束地表和管线变形。以西安地铁3号区间隧道为研究对象,首先采取经验法计算单线隧道引发的地表沉降,然后基于叠加原理预测双线隧道对地表沉降曲线的影响,之后利用FLAC^(3D)模拟不同浅埋暗挖工艺对地表和既有管线变形的影响。理论分析及数值模拟结果均表明,双线隧道引发的地表沉降呈"U"型曲线分布,且沉降槽宽度影响范围和地表沉降均较单线大;有限元结果亦表明,环形开挖预留核心土法宜作为该区间隧道的施工方法。最后通过现场监测分析表明,该施工方法能有效降低地表沉降和管线变形,对黄土地区该类隧道工程具有一定的指导意义和借鉴价值。

In order to ease the traffic pressure on the ground surface,majority cities develop the underground engineering. However the subway always is built under the municipal roads,and the pipeline under the ground is inevitablely effected. Some pipelines are need be migrated. In some cases,pipelines can not be migrated due to the objective conditions. Therefore,rational construction measures should be taken to ensure the surface sedimentation and the surrounding pipelines displacement within allowable standard range. Based on Xi'an metro 3 tunnel,firstly the surface sedimentation of the single tunnel are calculated by taking the experience method,and then the settlement of the double line are drawn by using the superposition principle. Secondly the surface sedimentation and the resulted pipeline deformation are studied by employing the different excavation methods based on the FLAC^(3D)simulation model. The theoretical analysis and the numerical simulation results show that the surface subsidence of the double line tunnel is 'U'and the settlement trough. The maximum surface subsidence are big than the single tunnel. Moreover,the numerical simulation results show that the ring cut method are employed by comprehensive analyzing of the other elements. Finally,the field monitoring results show that the construction method can effectively reduce the surface subsidence and its influence on both the adjacent bridge pile foundation. Our study is valuable and provide reference in guiding the tunnel project in the loess area.