Large Span Subway Station Construction Technology Base On Expansion Excavation Under TBM Running Tunnel

TBM method are more and more used in subway construction.But TBM is mainly confined to the running tunnel,unable to exert its advantages in the station construction.One of the key problems to be solved for subway construction is the contradiction of construction time limit for station and running tunnel constructed by TBM method.This paper discusses subway station construction technology based on expansion excavation in the case of TBM driving through station.This paper is based on TBM construction process,considering factors such as the thrust of shield,the cutterhead torque,the friction force between shield and soil,the weight of shield,the pressure on surrounding rock exerted by gripper shoe,to reasonably simulate and analyze the process of TBM construction on the three dimension.The research content consists of the following aspects in combination with Hongtudi Railway Station of Chongqing Metro Line6.1.Combining with the engineering field,the three-dimensional numerical simulation method of TBM construction is established and used;Through the comparison of several construction schemes,the following problems such as upper excavation forms before The TBM driving through station,whether to add temporary inverted arch and the thickness of column etc are solved.construction schemes are optimize overall,the contradiction of construction time limit for station and running tunnel constructed by TBM method is solved and the construction efficiency is improved.2.Through numerical calculation and site measurement,the mechanical behaviors of each excavation step is analyzed.the influence on the upper structure during TBM driving through station and the influence on TBM tunnel support structure during the upper expansion excavation are Mainly discussed.the stress of the supporting structure in the high arch foot position and the appropriate reinforcement measures are discussed and analyzed.the tunnel displacement and surface settlement under the tunnel excavation step are also analyzed.3.Suitable and safe construction measures for the expansion excavation are put forward,including the controlling of blasting method and blasting parameters during the excavation of the lower bench,the design of form working jumbo for the construction of arch second-layer liner and the measures and parameters of the floor strengthening.Through comparative test,the appropriate form of drainage at connection part of arch wall is determined.4.The tiems of monitoring measurement,measuring frequency and measuring standard appropriate for the project are put forward.