Study On The Application Of Finite Element In Tunneling Construction And Lining Design Of Soil Tunnel Considering Space Effect

At present,in terms of tunnels and underground engineering construction,China's technological level has been at the forefront of the world.The scale,number,geological conditions,and structural forms of the projects under construction are all facing unprecedented challenges.There are already mature theories for the design and construction methods of rock tunnels.The soil tunnels,all of factors which are the characteristics of low soil strength,large deformation,small self-supporting capacity and poor engineering properties,determine the complexity of the construction excavation and the stability of surrounding rock for soil tunnels.Therefore,for the soil tunnels,there has been formed no systematic or complete system in terms of engineering quantity or scientific research.The information and experience available for reference in the design and construction are limited.In this paper,it takes the Water Resources Allocation Scheme in North Hubei Province as the engineering background.The cavern section of Jihong Tunnel is the main research object.Considering the spatial effect of the tunnel and utilizing the virtual support of the excavation surface fully,with the help of the 2D finite element software and the principle of “generalized virtual stress method”,the tunnel excavation process was simulated and the dynamic simulation of the excavation process was realized.In addition,a summary analysis was made of the rock pressure calculation theory for existing deep and shallow tunnel and the basis of deep-shallow buried division.The calculation rules for the soil tunnels which is suitable for the project are used to determine the rules for the deep and shallow buried tunnels.The most dangerous section of the tunnel is obtained by using the established rules of the shallow-buried soil tunnel.The main conclusions are as follows:(1)Relationship between load release rate and deformation of tunnel surrounding rock: as the release rate of excavation load increases,the displacement of surrounding rock decreases gradually;when the excavation load is initially released,the displacement increment is maximum and the load release rate reaches a certain level.The increment of displacement is basically unchanged,and the displacement of surrounding rock increases steadily.(2)Due to the different stiffness of the different structures of the tunnel support structure,the internal forces undertaken are also different.The ratio of the moments of shear and squeezing of the sluice in the tunnel section of the Jihong tunnel to the steel arch is 1.04:1,and the ratio of axial force is 1: 1.73.(3)The surrounding rock pressure of the tunnel varies due to the deep and shallow burying of the tunnel.The surrounding rock pressure of shallow tunnels increases with the depth of the tunnel,and the surrounding rock pressure of the deep tunnel has nothing to do with the depth of the tunnel.That is,the surrounding rock pressure does not change with the buried depth of the tunnel.(4)The "Code for Highway Tunnels" specifies that the load sharing ratio of the secondary lining of the V-type surrounding rock is 60% to 80%,and that of the Jihong tunnel is 70%.Through the finite element analysis of the tunnel,70% of the load is satisfied.Actual project requirements.