Study On The Interaction Between Down-traversing Shield Tunnel Of Urban Railway And The Existed High-speed Railway

Urban railway system playing a role as the main artery to support the normal operation of city has been rapidly developed of large scale in big city on account of its characteristics of high speed, convenience, comfort, less land occupation, high carrying capacity and safety operation. At the same time, through the high-speed railway construction and transformation of the existing general speed railway, China has owned the world’s largest and fastest high-speed railway network. Unavoidably, the two lines will meet in some locations. In order to reduce the land occupation and reduce the impact on the existing traffic, and also to reduce the cost of the project and the influence on the surrounding environment, new urban railway line down-traverse the existing high-speed railway has become the main form. But down-traversing shield tunnel construction will lead to deformation of the high-speed railway, and track irregularity, affecting the operation stability and comfort of the passengers, also putting the train in danger. What’s more, and the dynamic caused by train operation will bring excitation process and tunnel operation disturbance. It is necessary to study the interaction between down-traversing shield tunnel of urban railway and the existing high-speed railway on Operation.Taking a real urban railway line down-traversing the existing High-speed Rail line as engineering background in this paper, the finite element software ABAQUS is applied to simulate the shield excavation process to study the settlement regularity due to excavation. Furthermore, based on the theory of vehicle-track coupling dynamics, a detailed dynamic model including vehicle-track-subgrade-shield tunnel is established to study the interaction between shield excavation and the existing high-speed railway on operation. The main research work and results of this paper are as follows:(1) Establish a ballastless track-subgrade-foundation excavation model and a vehicle-ballastless track-subgrade-down-traversing tunnel coupling dynamic model of large scale, detail and close to the actual project.Thanks to its constitutive model of rock and soil materials in ABAQUS, ballastless track-subgrade-foundation excavation model is established. Element birth and death technology is applied to simulate shield excavation process of soil excavation, shield tail void, segment installation, wall back grouting and so on. Based on the theory of vehicle-track coupling dynamics, the dynamic vehicle-ballastless track-subgrade-down-traversing tunnel coupling model is built through the explicit penalty contact properties module.(2) Reveal the settlement regularity of track structure due to shield excavation and study the influence of different depth and different excavation radius.Relying on the ballastless track-subgrade-foundation excavation model, the settlement regularity of track structure due to shield excavation is studied when shield tunneling and the high-speed rail lines are at different positions. Comparative analysis on different depth and different excavation radius are carried out, and an assessment combined with high-speed railway design specification is conducted to evaluate the uneven settlement value caused by excavation.(3) Analyze the dynamic response of track structure and down-traversing tunnel when vehicles pass by at different speed and study the response changes when shield tunneling and the high-speed rail lines are at different positions.Depending on the vehicle-ballastless track-subgrade-down-traversing tunnel coupling dynamic model of large scale, detail and close to the actual project, the uneven settlement caused by excavation is applied to the ballastless track to study the dynamic response of track structure and down-traversing tunnel when vehicles pass by at different speed. What’s more, an research on the response changes when shield tunneling and the high-speed rail lines are at different positions is also carried out. The results show that the dynamic indicators are within the safe range.(4) Discuss the dynamic response law of track structure with the excavation gap extension.In the ABAQUS model, the tie contact property is set between the track slab and the mortar layer out of the gap area to simulate the actual "bond" relationship and sine curve widely used in railway to simulate the gap. The dynamic response of each structural layer with gap size of0-15mm are researched...