Analysis And Study On The Influence Law Of Underpass Tunnel Excavation On Pile Foundation

With the continuous growth of the national economy,the people's living standards are increasingly improving,and more and more people are beginning to live in the city,which will bring great challenges to the city's transportation.The increasing tension of ground space makes people turn their attention to the exploitation and utilization of underground space.The construction of subway tunnels has eased this traffic pressure,but with the construction of subway tunnels,there will be more and more construction difficulties.As is known to all,there are numerous high-rise urban buildings and numerous underground municipal pipelines.The construction of subway tunnels will excavate the original soil-rock mass,which will inevitably break the stress equilibrium of the original stratum and settle and deform soil-rock mass.And the pile foundation in a certain range will be affected by the deformation of stratum,which will greatly reduce its safety.Therefore,how to ensure safety risk of the surrounding pile foundation is minimized while the construction of the subway tunnel is being carried out,which will have important scientific significance and practical value.In this paper,it takes the tunnel construction No.1 of Qianshan Road Station on the 2nd line of Hefei subway as the research background,and establishes the numerical simulation and the scene measured monitoring data through the MIDAS/GTS-NX finite element software to study the effect of the construction of channel on the surrounding bridge piles.The main work is to first summarize the current status of the underground cavern construction research at home and abroad and the influence mechanism of the channel construction on the pile foundation.A brief introduction of the MIDAS/GTS-NX finite element software is performed,followed by 3D modeling analysis.By studying the construction sequence of the tunnel,the construction footage and the distance of the excavation surface,the influence of the underground tunnel on the deformation of the stratum and the pile foundation was studied.The results show that due to the different distances between the left and right piles from the centerline of the tunnel,the different excavation sequences have different effects on the deformation of the pile foundation.Therefore,the best excavation sequence for controlling the settlement of the ground surface and the deformation of the pile foundation is: CRD 3-4-1-2.The scale to be excavated needs to be selected according to the construction period and the safety of the construction.Usually,the smaller the excavation scale,the better the control of surface settlement.The footage of the excavation surface has a great influence on the deformation of the pile foundation.When the excavation surface is far away from the pile foundation,the deformation of the pile foundation is small because of the less excavated soil based on the squeezing effect.When the excavation surface is close to the pile foundation,due to the lack of large amount of soil and the shrinkage of the lining,the deformation of the pile base is accelerated.