Numerical Simulation Study On Construction Of Saturated Loess Large Span Interval Tunnel In Lanzhou Subway

With the rapid development of China's economy,China's urbanization has also made great achievements.But at the same time,Some problem such as traffic congestion,urban transport infrastructure construction lag,urban traffic disaster prevention capacity is also gradually emerged,and these problem played a negative role to the further development of the city.Urban rail transit system is one of the most effective ways to alleviate the traffic congestion and improve the urban environment.It belongs to the green environmental transportation system and conforms to the principle of sustainable development.Like other major cities in China,Lanzhou City is also facing a similar problem,so hope to build Lanzhou subway project to solve these problems.As the subway in the western region of the loess formation,the first subway project started in Lanzhou City,which faces a series of problems.In this paper,the deformation of surrounding rock during the construction of saturated loess tunnel in Lanzhou area is studied based on the large span intervening tunnel in the rear section of Donggang station in TJ ?-16 area of Lanzhou subway station.By numerical simulation method,comparing and analyzing the stress field,surface subsidence,subsidence subsidence,peripheral convergence and supporting structure of saturated loess surrounding rock under the condition of fluid-solid coupling and uncoupling.According to the design parameters and engineering geological conditions of the construction site,established the CRD method model and two side-wall pilot tunnel method model respectively,and analyzed the whole process of the excavation support stage.Under the condition of fluid-solid coupling,the two side-wall pilot tunnel method is used to optimize the construction method in order to find the optimal construction method.The main research results of this paper are as follows:(1)Through comparative analysis,the results of the two cases are quite different.For the simulation of saturated loess,the effect of water must be taken into account.Otherwise,the result will be greatly affected.(2)Compared with the results of the CRD method and the double-wall guide method,in saturated loess tunnel,the control effect of six part CRD methods on surface subsidence and surrounding rock deformation is better than the double-wall guide method under the same conditions.Through the injection of concrete closure of the excavation face,two side-wall pilot tunnel method is slightly better than six part CRD method.(3)By comparing the different optimization methods of the two side-wall pilot tunnel method,for the control effect of surface subsidence and arch sinking,two side-wall pilot tunnel method along the reserved core-soil is the best than other cases;when the core-soil length is 1m,the control of deformation is relatively good.In summary,this paper take the actual project as the research object,make numerical simulation analysis of the shallow large span saturated loess tunnel,and put forward reasonable suggestions for the construction method,which can provide reference and guidance for the construction of the subway tunnel.