Study On Numerical Simulation And Stability Analysis Of A Foundation Pit Excavation Support In Lanzhou City

With the development of large-scale urbanization,the high-rise building structure has entered a new development period,and the excavation research of the deep foundation pit where the bearing structure is located is also particularly important.The geostress adjustment and deformation laws of deep foundation pits during excavation have been extensively studied by many geotechnical workers,and have achieved fruitful results in the theory and construction guidance of foundation pit excavation.However,for the northwestern region known as the Yellow Indigenous People,the research on the foundation pit stress and deformation mechanism during the excavation process of the silty loess in the high-rise commercial and residential buildings needs further study.It is well known that loess has the characteristics of humidification and softening.It is necessary to carry out precipitation treatment during foundation pit construction,and to ensure the safety of the superstructure and construction personnel to the maximum extent during the foundation pit excavation process,and its task is also arduous.For the foundation pit engineering in the city,the surrounding environment is often complicated,the lithology of the stratum is complex,there are many surrounding buildings,and the underground pipelines are dense.The construction of the foundation pit will bring certain safety hazards to the surrounding environment.Therefore,the problem of surface settlement and support structure stress during the construction of foundation pit engineering has always been the focus of research.Based on the deep foundation pit project of Lanshi·Haobusika in Lanzhou City,this paper has developed the precipitation design plan,earthwork excavation plan and foundation pit support plan.The actual measured data and numerical simulation are different through on-site monitoring.Under the condition of foundation pit excavation,the law of ground surface settlement,support structure stress and horizontal displacement of foundation pit were studied.The main contents and conclusions of this paper are as follows:Firstly,the relevant literatures at home and abroad were consulted,and the research status,stress characteristics and main classification of foundation pit excavation support were studied accordingly,with special attention to the working mechanism of composite soil nailing wall and prestressed anchor cable.And structural features.The main research contents and objectives of this paper are clarified.According to the geological profile and survey data,the stability of the site foundation and the engineering suitability are analyzed,and the comprehensive evaluation of the stratum is made,which provides a reference for the subsequent development of various schemes and numerical simulations.The precipitation of the foundation pit project has a profound significance for the stability of the foundation pit and is an important process in the construction process of the foundation pit.Combined with hydrogeological data,this paper has developed a precipitation design plan to ensure the safety of the foundation pit construction.At the same time,the earthwork excavation and foundation pit support schemes have been formulated to ensure the orderly implementation of the project.Using the finite element software MIDAS-NX to simulate the excavation and support process of the whole foundation pit,including soil nailing wall and prestressed anchor cable,etc.,focusing on the settlement of the surface around the foundation pit and the level of the pit wall.The characteristics of displacement,soil nail wall and prestressed anchor cable internal force change,the law of various index changes was studied,and the overall analysis was carried out with field measured data.The monitoring measurement can reflect the dynamic construction process most intuitively,and can clearly understand the stress of the supporting structure and the displacement of the foundation pit.By comparing and analyzing the results of the monitoring data and numerical simulation,the construction of the site is rationalized.Suggest.