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

TIAN Xiaoyan; LIU Jing; DAI Jianbo

Abstract：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 FLAC3D 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.