| In recent years,with the increase of the urban floating population and the continuous increase of the traffic pressure of the mass transit systems,the construction of the subway has been carried out in most of the capital cities and the first tier cities in China.But because our country city subway construction is generally started later than other under construction,the construction of the subway usually affected by site conditions and existing underground buildings,and subway lines often appear to cross the line of overlapping.Such as Shenzhen Metro first phase project from Luo station to Da station,as well as Guangzhou Metro Line 5 Sha staion to feng station and Shanghai pearl line overlapping tunnels,etc.When the subway line appears overlapping,second construction will cause the formation of the disturbances,second excavation of the tunnel will cause additional stress in the first construction segment.If tunneling is not controlled well,it is extremely easy to cause the surface subsidence,segment cracking and the segment leakage.This paper takes the Kunming city subway I project of KunMing Railway Station to ring road station interval overlap tunnel construction as background,and the construction control of overlapping tunnels with large slope,long distance and small net distance is discussed.The research contents of this paper are as follows:(1)Studied the existing overlapping tunnel projects and related research results,and combined with the characteristics of the construction of the related section,the problems in the overlapping tunnel construction are carried out and analysed.(2)Theoretical analysis and numerical calculation are used to study the influence of the interval overlapping tunnel construction.Through numerical simulation,the influence of shield construction on the environment is evaluated,including the formation displacement,the settlement of the building,the convergence of the tunnel and so on.After simulating the influence of tunnel construction on the first construction tunnel and the displacement of the formation,the monitoring measurement standard of the underground pipeline is determined,and the potential construction risk of overlapping tunnel construction have been found out and the corresponding treatment measures have been put forward.(3)According to the numerical results,combined with the other section of Kunming subway construction experience,the reinforcement method of the formation and monitoring standards have been put forward.By analyzing the monitoring data of surface subsidence and tunnel convergence in the tunneling process,the rationality of the auxiliary construction measures adopted in this section is verified.And then summed up the control technology in small-distance tunnel construction. |
