Study On The Track Deformation And Dynamic Response Under The Conditions Of Shield Tunnel Undercrossing The Existing Tunnel

With the rapid development of urban railway system and underground construction, the subway track of many large cities is gradually gridding, the intersection of metro tunnel has become inevitable. The newly built tunnels cause the deformation of the existing tunnel structure and track when it underneath passes the existing tunnel, and then, it will affect the normal operation of the subway. Therefore, it has a good reference significance for the practical engineering by systematically researching the deformation law of the existing structures and the track vibration response caused by the tunnelling projects.This paper carried out the following works on the basis of the current research:(1) calculating model of the existing tunnels vertical displacement caused by tunnel shield’s underneath passing was established by aiming at the orthogonal tunnelling working condition. And two-phase method was adopted, the first phase got the soil body elastic displacement caused by the positive propulsion force and the resistance to side friction of the shield construction by adopting numerical integration and on the basis of Mindlin elastic solution, and it solved the soil body elastic displacement caused by the gap of shield tail through sinksource method; the second phase converted the soil displacement caused by the above four factors into load, and it established the equilibrium differential equations of the newly built tunnels based on the Pasternak ground model, ultimately, it solved and got the vertical displacement of the existing tunnels cause by the shield construction of underneath passing tunnel.(2) The displacement and inner force of the track structure generated by wheel load effect were analyzed when there was the influence of underneath passing construction.On the basis of the traditional Winkler Elastic Foundation Beam Theory, it established double composite beam model of steel rail-monolithic roadbed, and respectively derivedthe general solution of model under the situation of having or without the influence of underneath passing construction, moreover, it also carried out mechanical analysis to the steel rail and the monolithic roadbed under different working conditions; considering the connection relationship among each layer of track structure, it considers the steel rail and the monolithic roadbed as free beam, and preliminarily discussed a mapping relation between steel rail deformation and tunnel deformation.(3) The vehicle-track coupled dynamic model was established based on multi-body dynamics theory, vehicle track coupling dynamic theory and finite element method. And the computing program DRIS was given out. The dynamic model considered tunnel and track deformation caused by underneath passing construction, so it can calculate and analyze the dynamic response of existing tunnel and vehicle quickly. Through the established dynamic model, dynamic response of the vehicle-track system before and after underneath passing construction were given. And the response on different speed and deformation characteristics were analyzed. The results showed that car body vibration acceleration, wheel-rail vertical force, rail dynamic displacement and rail acceleration increases with the increase of speed and the settlement amplitude. Under the condition of speed 80km/h and settlement wavelenght 14 m,the car body vibration acceleration was beyond the limit when the settlement amplitude was over 19.52 m. So in the actual projects,the settlement amplitude should be noted in particular.