Research On Forced Deformation Characteristics And Ground Settlement Law Of Double-track Shield Crossing Bridge Pile Foundation

In recent years,with the sharp increase in surface traffic pressure,many large and medium-sized cities have begun to lay out and improve underground rail transit networks.As an important part of underground transportation,subway construction must to be considered the impact on the surrounding environment.Most urban rail transit sections were constructed by shield tunneling.Since most cities did not consider the interaction between their underground structures and shield tunneling in the initial planning stage,shield tunneling through existing structures had become a major difficulty in shield tunneling construction.This paper took the potential height section of Hefei Rail Transit Line 4 as the engineering background.Aiming at the engineering problem that the shield passes through the bridge pile foundation;the numerical simulation and field monitoring were carried out.The focus was on the analysis of the bridge pile foundation caused by the shield construction,displacement patterns and deformation laws of stratum and structure.Numerical simulation results showed that the maximum horizontal displacement of the pile foundation occurred at a depth of about 25 m.Piles 1-4 were the closest to the excavation surface,resulting in a larger horizontal displacement increment,and piles 5-12 were the farthest from the excavation surface,and the horizontal displacement increment was small.Further analysis of the internal force of the pile body shows that the maximum axial force appears at pile 6 and the maximum axial force is-1973KN(pressure).The two maximum values of shear force both appear on the No.6 pile,which were located on the upper and lower surfaces of the tunnel,respectively,about 99KN and-91KN.Pile bending moment at the beginning when the tunnel construction surface was far from the pile foundation,the pile bending moment did not change,as the shield construction continued,when the shield construction surface was close to the pile foundation,the absolute value of the pile foundation bending moment Linear increase,and finally when the shield construction was far away from the pile foundation,the pile body bending moment remains stable and no longer develops.Analyzing the final surface settlement of the points on the two straight lines,it was found that the surface settlement around piles 1 to 4 was the largest,with an average settlement of 6.5mm,and the average settlement of the ground near piles 5 to 8 was 6mm,and the average settlement of the ground near piles 9-12 was 6.3 mm.Field monitoring results show that the displacement of bridge pile foundations on both sides of the shield tunnel increased with the gradual advancement of the excavation surface,while the displacement of the bridge pile foundation located in the middle of the shield tunnel first increased with the advancement of the excavation surface.The phenomenon of reduction indicated that during the actual shield tunnel construction,the vertical displacement of the bridge pile foundation in the middle of the shield tunnel was affected by the successive disturbances of the left and right tunnels,which was consistent with the numerical simulation results.From the measured displacement curve,it can be concluded that the displacement of each measuring point gradually increases until it becomes stable,and the maximum value is less than the control value,which meets the requirements of the specification for surface settlement.Figure 51 table 10 reference 62...