Numerical Simulation On Deep Exaction With Complicated Surrounding In Lacustrine Sedimentary Soils

With the rapid development of urbanization process and social economy,in order to meet the requirement of the building's embedded depth,structural seismic,civil air and make full use of underground space,development and utilization of urban underground space is an inevitable trend of city development.Lacustrine sedimentary soils distributed rather widely in Dianchi Lake basin.Deep foundation pit excavations in densely built area will have bad influence of complicated environment conditions.Therefore the research on Deep foundation pit excavations with complicated environment conditions in lacustrine sedimentary soils is of important significance.In order to study on the influence of complicated environment conditions by deep foundation pit excavations in densely built area,this thesis did research on the foundation pit engineering in NO.5 Building of The First Affiliated Hospital of Kunming Medical University.This thesis studies the usage of finite element theory numerical simulation.The m-method is used in the supporting design of the certain extra-large foundation pit engineering.Then three-dimensional finite element analysis of the excavation during constructing and supporting processes is carried out based on coupling seepage-stress effects.According to the most unfavorable conditions,analyzes the seismic response of the certain extra-large foundation pit engineering.The results indicate that(1)The nonlinear constructive model of Modified Mohr-coulomb includes loading modulus and unloading modulus,which conforms to the reality of Foundation Pit Excavation.(2)The supporting structure of pile-brace is selected in complicated environment conditions through comparison analysis based on all kinds of supporting structures.(3)Outside soil Settlement increases as the excavation depth increases,the maximum value appears in a section of distance beyond retaining pile and the distance from the crack tip increases while the moving rate decrease as the excavation depth increases.(4)The rebound value of the pit bottom increases with the longer distance from the retaining pile,reaching its maximum value in the middle of the pit.(5)The horizontal displacement of retaining pile increases as the excavation depth increases and changes like a “parabola”in the vertical direction.The biggest deformation of the retaining structure occurs near the excavation face.(6)The deformation of buildings and subway tunnel near the foundation pit is in the range of standard requirement.(7)The change rate of pore pressure showes a decreasing tendency with the increase of the distance from foundation pit.With dewatering of the foundation pit,the shape of pore water pressure line shows as a “U” gradually.(8)The deformation,Acceleration,maximum stress of Supporting Structure has obvious fluctuation.The failure process of Supporting Structure has time-related characteristics.The deformation of soil and buildings around the foundation pit have regionality.Innovative point in this thesis: considering the contacting characteristic of the pile-soil,analyzing the influence on deformation of buildings and subway tunnel near the foundation pit by dewatering and excavation,analyzing seismic response dynamic stability of the foundation pit.