Analysis Of Deformation Of Underlying Tunnel Caused By Dewatering And Excavation Of Deep Foundation Pit And Its Comparative Analysis Of Influencing Factors In Phreatic Stratum

Multi-storey,high-rise,super high-rise buildings or structures continue to emerge,and various large-scale projects such as subway stations,railway stations,and open-excavation tunnels are increasing with the rapid development of urban construction in China.The construction becomes more and more difficult,and the impact on the surrounding environment cannot be ignored with the increasing scale of underground space development.How to predict and quantify the impact on the surrounding environment induced by dewatering and excavation of deep foundation accurately and reduce the incidence of safety accidents,which has always been a difficult and important issue,and it is also a subject that needs to be studied and solved.This paper takes the dewatering and excavation of deep foundation pit in phreatic stratum as the engineering background,takes the principle of effective stress and the Mindlin solution of elastic half-space as the theoretical basis,and uses FLAC3D5.00 numerical simulation software and MATLAB as the means to focus on the following research:(1)The additional stress increment of the existing tunnel was calculated theoretically caused by dewatering and excavation of deep foundation pit.The theoretical analysis of the vertical deformation of existing tunnel caused by dewatering and excavation is performed through MATLAB based on the Pasternak foundation beam model vertical deformation equation of the existing tunnel,which was compared with the FLAC3D5.00 numerical simulation results to draw relevant conclusion that is simulation value is much larger.(2)The vertical deformation of the underlying tunnel,the surrounding ground settlement and the lateral deformation of the retaining structure were studied by numerical simulation methods with the background of the actual engineering,and the deformation mechanism was analyzed.(3)For the influence of dewatering and excavation conditions of deep foundation pit on the deformation of the existing underlying tunnel in the phreatic aquifer stratum,four different methods that are improving the excavation method and dewatering method,tunnel lining stiffness and uplift pile length were used to analyze the deformation of the existing underlying tunnel,and draw the optimal dewatering and excavation and parameter values that are meaningful to the engineering practice based on FLAC3D5.00 numerical simulation.