The Influence Of Excavation Face Spacing On The Surface Subsidence Of Double-track Shield Tunneling

As we all know,the construction of double-track shield tunnel is carried out in the soil,which will affect the soil around the tunnel and the buildings.Nowadays,most of the construction units have distanced the construction spacing between the front and rear excavation faces of the double-track shield tunneling to reduce the influence of shield tunneling on the surrounding soil,but this is bound to affect the construction period and progress.If the construction method of simultaneous excavation of double-track shield tunnel is adopted,the soil around the tunnel will be seriously loosened and deformed,thus endangering the safety of neighboring buildings.Therefore,on the premise of minimizing the disturbance of shield tunneling to the surrounding soil,it is the research focus of this thesis to select a shorter construction distance of shield tunneling double-track tunnel excavation face to accelerate the construction progress and reduce the construction period.This thesis in Beijing subway line 19 Xin ~ Cao shield interzone as the engineering background,in the actual construction of the project,the shield interzone adopts the method of 150 m between the excavation face of the shield tunneling front and rear.It is found that the construction method tends to be conservative,resulting in a long construction period and the construction progress is slow,the long-term construction also had an impact on nearby residents’ life.This article will research the disturbance regularity of strata deformation caused by shield tunnel construction,and different tunnel excavation face was simulated by FLAC3 D,find out the best front and rear distance between the double-track tunnel excavation face of shield construction,make it in as far as possible to shorten the construction period,and reduce the disturbance of shield construction of tunnel surrounding strata.The specific research contents and conclusions are as follows:(1)The surface subsidence of the new~grass shield was monitored,and the monitoring results were processed into data,so as to analyze the regularity of the influence of the subway double-track tunnel construction on the surface,and to provide theoretical support for the results of the numerical analysis;(2)FLAC3D software was used to simulation the impact of different distance of the excavation face on strata and Compare the differences of subsidence between them to find out the best front and rear distance between the double-track tunnel excavation face of shield construction;(3)The on-site monitoring data were compared with the FLAC3 D numerical simulation results to verify the authenticity of the model,and compared the differences between the results and the actual monitoring data to analyze the reasons;(4)By comparing the calculation results of different front and rear distance between the two excavation faces,it is found that when the distance between the two excavation faces is less than 15 m,the influence on the surrounding soil is not different from that when the two tunnels are excavated simultaneously and synchronously.When the distance between excavation faces is more than 90 m,the influence on surrounding soil is not different from that of the tunnel alone.Therefore,this project can select the synchronous excavation method with the excavation face distance of about 90 m between the two tunnels to shorten the construction period reasonably.