Research On Construction Risk Control Of Primary Support Arch Cover Method In Deeply Buried Metro Station In Soft Rock Stratum

The buried depth of bedrock in Dalian,Qingdao,Chongqing and other regions is relatively shallow,which is a typical "upper soft and lower hard" stratum.The construction of subway stations generally adopts the double-side guide method and arch cover method.With the construction of rail transit projects,engineering designers have proposed the primary arch method based on the traditional arch method.At present,the traditional arching method has been successfully applied in Dalian,Qingdao,Xiamen,Chongqing,Guiyang and other places,but the engineering cases and research results of the primary arching method are very few.The design and construction are lack of experience for reference.The Hongyancun Station of Chongqing Rail Transit Line 9 is buried at a depth of about 70 ～ 100 m.It is a deep-buried station.The first arch arch method was used for the first time during the construction process.The study provided examples.In order to carry out further research on the arch cover method and continuously expand the scope of use of the arch cover method,at the same time provide guidance for the safety construction of Hongyancun Station,this article takes Chongqing Rail Transit Line 9 Hongyancun Station as the basis and focuses on the soft rock stratum Risk control research was carried out on the construction of the first-arch arch cover method of deep-buried subway station.The main research contents of this article are as follows:(1)Use WBS-RBS risk coupling analysis method to decompose and couple the working structure and risk structure in the construction process,find the risk sources in the construction process of the primary support arch method of the deep buried subway station,and then use the analytic hierarchy process to determine each risk source To find the risk sources that have a greater impact on the construction..(2)A two-dimensional analysis model was established to analyze the stability of the deep-buried subway station when it was constructed with the primary support arch method.At the same time,the strength reduction method was used to find the limit state of the tunnel and its failure mode was analyzed.(3)Establish a three-dimensional numerical model to optimize the excavation of the left and right guide pits and the bottom of the arch at the initial support arch method,and at the same time,study the timing of temporary support removal to reduce the possibility of risk and loss.(4)Three-dimensional models with burial depths of 50 m,100m and 150 m were established respectively,and the physical and mechanical parameters of the weathered sandy mudstone in Chongqing area were sampled and combined according to high,medium and low positions to form 9 analysis conditions,and different burials were calculated respectively.Under the deep conditions,the displacements of the characteristic points around the cave under nine working conditions are analyzed mathematically according to the t distribution to obtain the absolute limit displacement value and the relative limit displacement value of the characteristic points around the tunnel to establish the depth of the soft rock formation.Deformation control standard for the construction of the first arch arch method of buried subway station.