Study On Deformation Law And Control Of Subway Station Excavation Using Primary Support Arch Cover Method

Guiyang is located in the "soft-upper and hard-lower" strata and many metro stations are located in the Dolomites as a whole in the city.In view of that soft soil exaction method is too conservative,the constructors put forward the primary support arch cover method.The primary support arch cover method is a novel of excavation and support and its excavation method and surrounding rock stability characteristics during the excavation process remain to be studied.For the Youzha Street Station in Guiyang,according to the methods of field test and numerical simulation,by taking ground surface settlement and deformation as the main research indication,this paper study mechanical behavior during excavation and applicability of the primary support arch cover method.In this paper,the innovation and results are as follows:(1)Relying on the example of the Youzha Street Station in Guiyang that excavated with the primary support arch cover method,monitoring surface displacement,cave convergence,arch sink in excavation process.The resuits show that the surface subsidence,the cave convergence,arch settlement in excavation process meet the national standard and the construction requirements and the primary support arch cover method is applicable in such strata.(2)The finite element numerical model of metro station excavated with the primary support arch cover method is established.The station excavation is simulated according to on-site construction process to calculate the ground settlement,the clearance of the cavern,the subsidence of the cavern,and the vertical displacement of the baseplate.Comparing with the on-site monitoring data,it is concluded that:(1)The numerical calculation results are basically consistent with the monitoring results,verifying the correctness of the numerical model;(2)Combined with the surface displacement,the arch displacement,the cave convergence simulation results and so on,comparing with on-site measured data,the conclusion is drawn.The removal of the temporary support and the excavation of the core soil caused the largest deformation of the station structure and surface,and it is the most important process.The excavation of the left and right guide tunnels has minimal impact on the station structure and the upper surface.(3)Using the finite element analysis model,the subway station construction method has been optimized.The results show that reducing the length of the footage and increasing the stiffness of the support can significantly reduce the deformation rate and total deformation of the surrounding rock and support during construction.Based on this,the construction parameters of the initial arch cover method were optimized.The above research has important guiding significance for analyzing the deformation law of subway station during the process of excavating subway station by the method of primary arch cover,and perfecting and optimizing the construction design of excavation with the method of primary arch cover.