Settlement Analysis And Controlling Of Railway Tracks Induced By Shield Tunnel Crossing Under Railway Track

With the expansion of urban subway tunnels and high-speed rail construction scale,the construction of subway tunnels under existing railway lines is also becoming increasingly common.The construction of the new tunnel will inevitably cause the settlement and deformation of the existing railway subgrade and track,and affect the safe operation of the train.Therefore,the deformation law of subway tunnel under existing railway and the interaction mechanism between tunnel,subgrade and track are studied.Formulating scientifically methods of the corresponding tunnel settlement control in tunnel construction is very necessary.First,the first stage is to predict surface subsidence.In order to obtain more accurate settlement results,in this thesis,Peck empirical formula and Verruijt complex function are combined to predict the surface subsidence,the influence of different construction parameters on surface settlement is also considered.At the same time,the method of numerical calculation is used to verify the theoretical prediction.Secondly,the second stage is to predict the track settlement.The method for calculating track settlement caused by uneven settlement of subgrade based on continuous elastic point supported beam model,which take the ground settlement as the nonlinear boundary condition of track settlement to predict the settlement of the track.The influence of the corresponding construction parameters on the settlement of the track is also considered.Then,based on the ride comfort of track,the control standard of track settlement for different construction parameters is put forward,and the corresponding settlement control measures are also worked out.Finally,applying the two stage analysis method in shield tunnel crossing under railway track section between Fuzhou Metro Line 1 station Luohanshan station and Fuzhou railway station.And compared with monitoring data,the reliability of the method of track settlement is verified.The main conclusions are as follows:(1)Under the condition of changing the construction Parameters,the correlation coefficient of the surface subsidence curve obtained by fitting the Verruijt complex function with the Peck formula is more than 0.98.The prediction method can take into account the elastic modulus E and Poisson's ratio ? of the soil,which is more reliable than the traditional Peck formula given the settlement trough width coefficient i by the experience.(2)The ground settlement caused by shield tunnel construction occurs mainly in three stage include before the excavating face,during shield through and after the period.The ratio of soil loss and Poisson's ratio has a great influence on the surface settlement,and has little influence on the width of the settlement trough.(3)The inhomogeneous settlement of the ground surface is taken as a nonlinear boundary condition for the settlement of the track,the analytic solution of track settlement caused by shield tunnel construction of through ballasted railway is deduced.The influence of construction parameters on track settlement is obtained,it is similar to the law of settlement of Subgrade.And the rail stiffness and ballast stiffness values provided relevant suggestions.(4)In this thesis,the two phase analysis method is applied to the related projects of Fuzhou Metro Line 1,and the error of track settlement of the prediction and field monitoring is less than 8%.The applicability and correctness of the method in this thesis is used to predict the settlement of soft ground in Fuzhou metro.