Research On Construction Technology Of Shield Tunnel Under-crossing Existing Railway And End Reinforcement Technology In Watered Sandy Stratum

With the rapid development of the economy,China's urbanization construction has been accelerating.Due to the huge effect of mitigating urban traffic pressure and driving high-quality sustainable development of the city,more and more big cities have started to build subways.The design and construction experience of other regions cannot be used during construction,because of the different characteristics of the watered sandy stratum in various regions.Based on the shield section of the West Second Ring Road Station to the Kongjiaying Station of Hohhot Metro Line 1,this paper studies the construction problem of shield tunneling in the watered sandy stratum of Hohhot.The main research contents are as follows:(1)Based on the engineering of the running tunnel under-crossing the existing railway project,the numerical simulation method is adopted.Firstly,the influence law of the soil chamber pressure,grouting pressure and grouting range on the existing railway is analyzed by the single factor variable method: the increase of soil pressure,grouting pressure and grouting thickness can better control the settlement and orbital height difference of railway.Secondly,the sensitivity of the soil chamber pressure,grouting pressure and grouting range to the deformation of the existing railway is obtained by the extremum difference analysis method: grouting pressure> grouting thickness> soil silo pressure.(2)Through the theoretical analysis and engineering analogy method,the calculation method of soil chamber pressure is given by the method of water and soil division,and the calculation formulas of top thrust,cutter head torque,soil discharge,grouting pressure and grouting amount are determined.After substituting each parameter,the control range of each parameter in the undercrossing construction is given.According to the actual construction,the tunneling speed and the cutter head speed are determined,and finally verified according to the actual monitoring results.(3)On the basis of summarizing the existing theory of shield end reinforcement and analyzing the force characteristics of the end soil,based on the thin plate theory in elastic mechanics,the calculation formula of the reinforcement range of the shield end is derived and successfully applied to the actual project.The research results of this paper not only effectively ensure the construction of the shield section,but also accumulate experience for the subsequent construction of Hohhot subway.