Research On The Influence Of Tunnel Crossing Existing Shoring Structure On Buildings At The Exit

With the great progress made in urbanization in China,more and more tunnels appear on the existing retaining walls because of the limited room for structures.In order to reduce the influence of urban tunnel construction on adjacent buildings,it is necessary to study the reasonable design scheme.Based on the background of the Leijiapo overpass tunnel project in Yuzhong district,Chongqing,this thesis carries out the research and discussion by means of theoretical analysis and numerical simulation combined with the actual site.The main contents and conclusions are as follows:(1)Introduce the engineering background,provide the basis of simulation calculation and relevant principles: systematically introduce the engineering background of the Leijiapo overpass in Yuzhong district,Chongqing from the aspects of engineering design,tunnel and reinforcement system construction method,and provide the initial basis for numerical simulation and structural optimization.(2)Numerical simulation method is used to simulate the influence of pile foundation of bridge at different adjacent positions during tunnel excavation.It is concluded that the excavation of the tunnel with the exit has a great influence on the bridge inside the retaining wall.The closer the pile foundation of the bridge is to the entrance of the tunnel,the more obvious the influence of excavation on the strata will be.However,when the pile foundation is located in the soil outside the retaining wall,it has little influence on the pile foundation due to its large space distance and the excavation of natural tunnel without connection with the retaining wall.(3)It is suggested that the bridge pile foundation should be selected to exit the tunnel when it is located outside the retaining wall.When the bridge pile foundation is located inside the retaining wall,it should be controlled to exit the tunnel at a position more than 5m away from the retaining wall to reduce the disturbance of bridge pile foundation during tunnel excavation.(4)The influence of tunnel excavation on the bridge pile foundation in the middle of the two tunnels is far greater than that on the two sides of the bridge pile foundation,numerical simulation shows that the main risk of this section is surface subsidence,so it is suggested that grouting should be used to reinforce the bridge pile foundation at the entrance of the tunnel.(5)The influence of changing the position of bridge pile foundation level is greater than that of the bridge pile foundation into the depth of the rock.(6)The influence of four different reinforcement schemes on the displacement and stress of adjacent buildings is simulated,the main effects are obtained,and the corresponding suggestions are as follows: Grouting reinforcement can significantly reduce the horizontal displacement and ground settlement of bridge pile foundation caused by tunnel excavation;Adding beams and prestressed anchor cables has little effect on the displacement of existing bridges,but it can reduce the horizontal displacement of the top of pile-plate retaining wall;Gravity retaining wall is mainly used to reduce the horizontal displacement from the middle of the existing pile-sheet retaining wall to the outside of the wall.(7)The calculated results are compared with the measured monitoring data,and the deformation law is roughly the same.Although there are some errors in the cumulative deformation,the value is within a reasonable and controllable range,which proves that the simulation results are reliable.The research results can provide reference for similar projects.