Analysis Of The Stability Of Hole Soil In Deep Shield Launching And Construction Method

With the development of city, pressure of ground traffic is more and more big. To build the subway has already become the primary way to solve the traffic problems in developed cities. There are many developed cities which have the situation that several subway lines crossed, This would be a new subway station or tunnel must wear under existing station and interval,it must result in the subway tunnel buried depth increases. At present,the construction method of deep buried metro tunnel is shield method normally. Shield originating is one of the important steps in the process of shield construction, also is one of the most prone to accidents. In the deep buried condition, it is difficult to reinforce end well soil, and is difficult to control the reinforcement effect. There is the phenomenon of gushing water and sand When Chiselling wall at the hole, and it is easy to occurre sfety accident. In view of the above problems, to determine the depth limit of soil tunnel by methods of numerical simulation and theoretical analysis in the paper. Analysis of the deformation law of hole soil in deep shield launching and analysis of the design methods of the underground continuous wall of deep shield tunnel and construction methods. The specific contents include four aspects as follows:(1) To determine the depth limit of soil tunnel.To determine the depth limit of soil tunnel by methods of numerical simulation and theoretical analysis. According to the Protodyakonov’s theory of failure model of arch collapse, introduce relevant hypothesis, have derived the relationship between the height of arch collapse and the depth of tunnel; Put forward the tunnel packing theory, introduce the coefficient of expansion of soil, have derived the calculation formula of the rch collapse height, and put it into the relationship between the height of arch collapse and the depth of tunnel. Finally, get the depth value can be used as the depth limit of soil tunnel. By the method of three- dimensional numerical simulation, to analyse the curve vertical stress ratio of soil above the tunnel and depth of tunnel and the curve of surface subsidence. Through the comprehensive and comparative analysis, get the depth limit of soil tunnel.(2) Analysis of the deformation law of hole soil in deep shield launching and influence factors.1) By the three dimensional numerical simulation software FLAC3 D, after destruction of the underground continuous wall of deep shield launching hole, analysis of deformation of hole soil, surface subsidence and the range of collapse area of hole soil,determine the height of collapse of hole soil.2) To analyse that is three factors of tunnel depth, tunnel diameter and elastic modulus of soil impact on soil deformation and surface subsidence, compare the influence degree of tunnel depth, tunnel diameter and elastic modulus of soil.(3) The design and research of the underground continuous wall of deep shield tunnel.1) Experimental study on connection of GFRP bar and steel bar.Through the uniaxial tensile test of GFRP bar and steel bar, analysing the connection properties of U type buckle, Put forward the reasonable quantity of U type buckle which connect GFRP bar and steel bar, the spacing between the U type buckle, and technology of connection.2) According to the active earth pressure of soil of hole collapse area, Checking the bearing capacity of normal section and oblique section which is the underground continuous wall of reinforced concrete and GFRP concrete. Put the specific recommendations to the structural reinforcement of the underground continuous wall at deep buried shield.(4) Study on construction method of shield tunnel hole1) The auxiliary construction method of shield tunnel hole——Installing the extension of steel ring. analyse the theoretical length of steel ring, Put forward the calculation formula of theoretical length of steel ring, and size structure and installation process of steel ring.2) The sealing method of shield tunnel hole. Through the Similar model test of shield hole water pressure, analyse the sealing performance of the sealing device of shield hole. To get the test results of air pressure and water pressure, The ratio of shield diameter of model test and shield diameter of project as similarity ratio. Through similarity ratio, the parameters of test results are applied to actual project, it can provide reference for the Sealed air bag initial pressure setting of shield launching and receiving. The two cases of shield launching with or without steel collar, put forward the structure of rubber cord gasbag as the hole sealing device.3) By using the method of numerical simulation, Study on the influence of Shield Thrust of deep buried shield launching on ground settlement and deformation of soil along the direction of excavation.4) After the establishment of earth pressure of deep buried shield launching, according to the active earth pressure of the tunnel face collapse soil, calculating the earth pressure of shield, then determining the range of earth pressure.