Research On The Influence Of Bridge Pile Construction On Deformation And Segment Characteristic Of Adjacent Subway Tunnel

In recent years,with the development and utilization of urban underground space and the continuous extension and improvement of the above-ground viaduct traffic network,the number of new bridge piles adjacent to the operating subway tunnels has increased.The construction of bridge piles will inevitably cause soil disturbance and deformation,resulting in additional deformation and internal forces in the adjacent subway tunnel,which poses a great threat to the safety of the tunnel structure.Based on this,the paper takes the reconstruction project of Fengqing Avenue in Hangzhou as the background,and explores the influence of bridge pile construction on the longitudinal and transverse deformation and segment characteristic of the existing subway tunnel through theoretical calculation and numerical simulation.The main research results and innovations are as follows:(1)A simplified mechanical model for bridge pile construction is established,and the revised calculation formula for each additional force in the construction of full-length casing cast-in-place piles is proposed.Based on the Mindlin stress solution and two-stage analysis method,the additional stress and longitudinal deformation of the existing tunnel caused by the bridge pile construction are obtained.The theoretical calculation results are in good agreement with the measured data.The dynamic change law of longitudinal deformation of adjacent subway tunnel in the whole process of bridge pile construction is discussed,and the length and diameter of bridge piles and the relative distance between piles and tunnels affect the deformation development of existing tunnel to varying degrees,and the construction influence zoning recommendations are given.(2)A calculation formula for additional confining pressure considering the stiffness of the existing tunnel is proposed.A three-dimensional numerical model of the tunnel segment was established,the change law of the transverse deformation and internal force of the tunnel segment caused by the construction of bridge piles are analyzed.It is found that the tunnel segment eventually produced horizontal movement,vertical settlement,counterclockwise rotation and vertical elliptical deformation.There is a linear proportional relationship between the diameter of the bridge pile and the deformation of the segment,and the relative distance between the pile and the tunnel is inversely proportional to it.Considering the initial ovality of the operating metro,the arching and magnification effect of the ovality can be more realistically reflected.(3)A three-dimensional numerical simulation model of engineering dangerous conditions is established to comprehensively evaluate the construction risk.It is found that considering the group piles construction superimposition effect,the deformation of existing tunnel has a larger numerical value and a wider range of influence,which is related to the distribution position and relative clear distance of the bridge piles.(4)The risk classification of adjacent subway tunnels and safety risk assessment standards for bridge pile construction have been established to comprehensively evaluate the impact of short-distance construction disturbance of bridge piles in terms of proximity,construction parameters,operating subway tunnel status,and dislocation deformation.The countermeasures and suggestions for the remediation and deformation control measures of the operating subway tunnel,project management,design plan,construction plan and monitoring and inspection are given.Figure[87]table[18]reference[148].