Study On The Effect Of Foundation Pit Construction On The Deformation Of Existing Road Pipe Jacking Tunnel

Due to the large-scale engineering construction in various cities,more and more foundation pit projects are located near existing tunnels.The close distance makes the contradiction between the two increasingly prominent.The construction of the foundation pit will affect the adjacent existing tunnels,because the change of the displacement field and stress field of the soil around the foundation pit will cause the stress redistribution,and then generate additional internal forces and deformation on the adjacent existing tunnels,the occurrence of internal forces and deformation will threaten the safe use of the tunnel.Therefore,it is of great significance to systematically analyze the influence of foundation pit construction on tunnel safety.In this paper,taking the foundation pit project of a tunnel with rectangular pipe jacking under a nearby road in zhengzhou city as an example,a numerical calculation model was established by using FLAC^3D to study the influence of foundation pit construction on the deformation of the tunnel with rectangular pipe jacking under a side road.The main contents and conclusions are as follows:?1?This paper summarizes the research literature of domestic and foreign scholars in four aspects:the influence of foundation pit excavation on the surrounding soil,the influence of adjacent buildings,the numerical simulation,the field monitoring,and points out the problems in the research.?2?The deformation form,generation mechanism and calculation method of foundation pit are studied.The theory and calculation method of tunnel deformation caused by foundation pit excavation are discussed.?3?FLAC^3D software was used to establish a numerical model for the foundation pit adjacent to the pipe-jacking tunnel.The internal force,deformation of the foundation pit support structure and the influence of foundation pit construction on the deformation of the existing undercrossing tunnel were analyzed under the support scheme of pile and anchor structure.By comparing and analyzing the differences between the simulation results of FLAC^3D software and the field monitoring data,the correctness of the model was verified.?4?According to the simulation,the influence of foundation pit construction on the horizontal deformation of the tunnel is stronger than that of the vertical deformation.The maximum horizontal displacement is 6.03mm,while the maximum vertical displacement is only 3.12mm.It can be seen that the construction of the foundation pit makes it easier for the pipe jacking tunnel to fail in the horizontal direction.?5?In view of the safety influence zone of existing pipe jacking tunnel construction adjacent to the foundation pit based on pile-anchored support technology,the corresponding construction countermeasures are proposed,that is,to reinforce the soil in the passive area of the foundation pit by rotary jet pile,so as to reduce its influence on the pipe jacking tunnel.The research of this paper has certain reference significance to the design and construction of similar projects.