Calculation Method For Deformation Of Double Beam On Elastic Foundation Beam Caused By Local Settlement And Its Application

In recent years,China’s urban rail transit has developed rapidly,and by the end of2021,the operating mileage has ranked first in the world.In this context,the impact of the construction disturbance of shield engineering on the environment is becoming more and more serious,including the inevitable problem of crossing the existing railway line in the upper part of the shield tunnel construction.The repeated disturbance of the tunnel construction under the shield is very easy to lead to undesirable phenomena such as uneven settlement of the soil under the existing upper railway track,resulting in excessive deformation of the existing track,while the existing railway operation has extremely high requirements for track and structural deformation,and the uneven settlement phenomenon of the soil below is easy to cause track structure damage and train derailment accidents.In this paper,the longitudinal mechanical response law of the existing railway track in the upper part is analyzed by constructing a mechanical model,and the displacement and internal force changes of the existing railway tunnel caused by the underpass construction of the shield tunnel are derived and calculated by the mechanical analysis theory method.The main work and achievements are as follows:1.Based on the Euler-Bernoulli beam theory,the basic assumption is put forward according to the interaction relationship between pavement structure and subgrade soil,the mechanical relationship of the actual project is simplified,and the mechanical model of the double-layer elastic foundation beam in the foundation subsidence area is established.Combined with symmetry analysis and material mechanics,the deformation calculation formula of pavement and subgrade structure in the case of foundation subsidence zone caused by uneven settlement of soil is derived,and the deformation calculation method of pavement and subgrade structure regarded as upper and lower beams within the subsidence area is established by considering the relevant characteristics of pavement subgrade structure and soil mass.This method can reflect the deformation characteristics of double-layer elastic foundation beams in the foundation settlement area caused by uneven settlement,and can be applied to the analysis of the influence of uneven settlement of soil caused by the underpass construction of shield tunnels on the deformation of pavement and subgrade structural layer,and the theoretical method obtained is more universal and clear.2.The normal distribution formula was used to predict the settlement of the top surface of the ballasted railway subgrade caused by the construction of new tunnels.Then,the track is treated as a beam on a non-tensile elastic foundation,and the calculation formula for the deflection deformation of the track caused by subgrade settlement is derived.By comparing with the experimental results of the indoor model and the on-site monitoring data,the theoretical model proposed in this paper is verified.The influence of horizontal angle between railway line and new tunnel,bending stiffness of rail,and width coefficient of settlement groove on rail deflection deformation on the top surface of the roadbed were discussed.3.The improved Winkler elastic foundation model was used to simulate the interaction between the track slab and the foundation,and the double-layer beam model was used to simulate the ballastless railway track structure,so as to establish a theoretical calculation model of the deformation of ballastless railway track caused by subgrade settlement,and the calculation formula of track deformation caused by tunnel underpass construction is derived by analytical method.By comparing the theoretical analysis results and numerical simulation data in this paper,the correctness of the theoretical model proposed in this paper is verified.Finally,the influence of important system parameters such as the amplitude and width coefficient of settlement groove on the top surface of the roadbed,as well as the intersection angle of railway and shield tunnel,on the deformation of railway rail caused by the underpass construction of shield tunnel is discussed.