Sensitivity Analysis Of Factors Affecting Deformation Of Foundation Pit Excavation In Subway Station

In recent decades,as the pace of urbanization in my country has accelerated,urban land use has become increasingly tense.In addition,with the increase of urban population,the means of transportation becoming more and more saturated.More and more cities begin to develop underground space.Among them,the construction of subway is an important part of the development of urban underground space,which has important practical significance for alleviating the problem of ground traffic congestion.Lanzhou City is located on the Loess Plateau in northwest my country.The geographical feature of "two mountains and one river" makes Lanzhou a slender belt along the east-west direction.Traffic jams are obvious,and the construction of subways is even more urgent.At present,the construction of rail transit in Lanzhou has just started,and there are few studies on the deformation characteristics of the excavation of subway station foundation pits under special geological conditions in Lanzhou.Therefore,it is of great significance to study the factors affecting the deformation of the deep foundation pit of Lanzhou Metro Station.This paper takes the deep foundation pit excavation and support engineering of a subway station in Lanzhou as the research object.Based on the pile-supported supporting structures used in the standard section of the foundation pit and the pit-in-pit section,the sensitivity research on the factors affecting the horizontal displacement of the supporting pile is studied.The main research contents and results are as follows:(1)By using PLAXIS 3D finite element software,selecting appropriate soil constitutive model,supporting structure model,load model,boundary range and boundary conditions,the 3D model of foundation pit in standard section and pit-in-pit section of subway station is established,and then the excavation and supporting conditions are simulated by finite element method.By extracting the deformation data of the supporting structure and surrounding buildings under various working conditions from the model,comparing and analyzing the actual monitoring data of the foundation pit,the deformation law of the foundation pit during the excavation and support process is summarized,and the model is verified by the measured data.(2)Introduced the orthogonal experiment design method,a commonly used multi-factor index comprehensive evaluation method.Orthogonal experimental design method is used to study the sensitivity of five supporting design parameters that affect the maximum horizontal displacement of the foundation pit pile in the standard section of the subway station.The sensitivity of these five support parameters was compared and analyzed by the range analysis method and the variance analysis method.The research results show that the sensitivity rankings of these supporting parameters obtained by the two methods are basically the same,indicating that the sensitivity evaluation results of these supporting parameters that affect the maximum horizontal displacement of the pile body are accurate.(3)Orthogonal experimental design method is used to study the sensitivity of six supporting design parameters that affect the maximum horizontal displacement of the pile body of the subway station foundation pit in the pit-in-pit section.The sensitivity of these six support parameters was compared and analyzed by the range analysis method and the variance analysis method.The research results show that the sensitivity rankings of these supporting parameters obtained by the two methods are completely consistent,indicating that the sensitivity evaluation of these supporting parameters that affect the maximum horizontal displacement of the pile body is accurate.