| In recent years,with the increasing density of urban rail transit network,more and more rail transit lines intersect in space.Shield tunneling method has been widely used in tunnel construction,but it will inevitably disturb the stratum in the construction process,thus affecting the deformation of existing tunnels,the running comfort and safety of trains.Therefore,this paper systematically studies the influence of shield tunneling on the deformation of existing subways and the dynamic response of train wheel-rail system.The main research work of this paper is as follows:(1)Based on the background of a shield tunnel passing through an existing subways tunnel in Beijing,a three-dimensional coupling static model of existing tunnel-soil-new tunnel was established.The life-death element method is used to simulate the shield excavation process,and the reliability of the model is verified by monitoring data.This paper studies the variation process of vertical/lateral deformations and vertical/lateral differences when shield tunneling is excavated to different locations of existing subways.It is concluded that the rail deformation rate and vertical deformation difference reach the maximum when shield tunneling is under the existing tunnel.After construction,the vertical deformation reaches the maximum and the lateral deformation is very small.(2)Based on the finite element model,the influences of the buried depth of new tunnel,the construction radius of shield tunnel and the horizontal distance between two lines of new tunnel on the rail deformation of existing subway were studied.Under the condition that the buried depth of existing tunnel remains unchanged,in a certain range,the increase of buried depth of new tunnel will increase the thickness of soil between the existing and new tunnels,so that the deformation of soil can be increased.And the influence on the vertical and lateral deformations of existing subways rail will be increased.The larger the shield radius of the new tunnel are,the greater the vertical deformation,lateral deformation and deformation difference of the existing subways rails are.The maximum vertical and lateral deformations of rail are 11.74mm and 1.73mm.The differences of vertical and lateral deformations are 1.11mm and 0.16mm.The smaller the horizontal distance between the two new tunnels is,the more obvious superposition effect of the disturbance caused by the construction of the right-line tunnel on the first construction of the left-line will be,and the greater the influence of the construction on the deformation of the existing rails will be.Among the three factors,shield radius has the greatest influence on the deformation of existing rails.(3)Based on the theory of multi-body dynamics,a spatial-coupling dynamic model of subways vehicles was established.The construction irregularities and superimposed irregularities in different stages under the most unfavourable conditions obtained from static analysis were introduced into the dynamic model.The influences of shield construction process,the amplitude and wavelength of rail deformation on the dynamic response of wheel-rail system were studied.The results show that the safety and stability of vehicle operation are not affected at all stages,and the most disadvantageous construction stage is when the shield tunneling on the right line is directly below the existing tunnel.With the increase of rail deformation amplitude,the dynamic response of wheel and rail increases slightly.When the maximum vertical deformation,vertical deformation difference,lateral deformation and lateral deformation difference of rail reach 91.5mm,11.12mm,17.33mm and 1.62mm respectively,the train can run safely with low comfort degree.Changing the wavelength has a great influence on the safety of train operation.The shorter the wavelength is,the greater the dynamic response of wheel and rail is.When the wavelength is 40m,the derailment coefficient and wheel load reduction rate exceed the limit,resulting in poor vehicle safety. |
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