Study On The Disturbance And Stability Of Shield Tunnel Under Taiyuan Metro Tunnel Crossing Yingze Lake

Compared with land tunnel,underwater shield tunnel has complex engineering geological and hydrogeological conditions and extremely high control standard of construction deformation,which makes it more difficult to construct,at the same time,it is extremely difficult to control and predict the stability of the tunnel.For the first time in Taiyuan region of underwater shield tunnel construction,the lack of related construction experience,combined with the wear of Yingze lake mainly through glue powder soil of shield tunnel,local for permeability is strong,the poor stability of silty sand layer,weaken the groundwater formation strength,excavated plane instability prone to collapse and even water penetration formation flooded the severe accident of the tunnel.Therefore,it is necessary to study and analyze the stability of the shield tunnel under the water of Yingze lake,and predict it accurately.Taking Taiyuan metro line 2 of shield tunnel under wear Yingze lake project as the background,the numerical simulation software to establish the finite element model of underwater shield tunnel,explore the underwater determine appropriate parallel tunnel longitudinal excavating safe distance,to reduce the double underwater shield tunnel excavation disturbance of superposition effect,to ensure the stability of the shield tunnel.Through comparative analysis,the increase of longitudinal excavation distance weakens the disturbance superposition degree of double-track tunnel excavation,and reduces the stress and deformation of strata and duct pieces.Under the analysis and discrimination indexes of duct piece deformation,lake bottom deformation and plastic zone,the critical value of longitudinal excavation spacing of underwater double-track tunnel is at least 30 annular duct pieces,that is,36 m is relatively safe.On the basis of safe longitudinal tunneling spacing,the influence rules of overburden thickness and lake depth on the stability of underwater tunnel are analyzed,and the results show that the variation of parameters does not affect the trend of duct piece deformation,internal force of duct piece and bottom deformation.The increase of the overburden thickness will increase the deformation and internal force of the duct piece,but will reduce the bottom settlement.The increase of the depth of lake water will increase the deformation of the lake,internal force and bottom settlement of duct piece.Using single factor analysis method,study the tunneling pressure,the grouting pressure and grouting layer thickness on the influence law of underwater tunnel stability,the results show that a certain range,the increase of tunneling pressure and grouting pressure and the decrease of the thickness of grouting layer can effectively reduce the deformation of duct piece and bottom settlement of the lake,but excessive driving pressure aggravates bottom settlement of the lake,and the growth also increases gradually.Based on the orthogonal design scheme,to cover soil thickness,water depth and tunneling pressure,grouting pressure,grouting layer thickness for the input,duct piece vault subsidence,arch bottom uplift and horizontal convergence for the output,compiled can accurately predict the deformation of underwater shield tunnel duct piece neural networks,used for dynamic engineering design and construction,has the actual engineering significance.