Research On The Impact Of Changchun Metro Foundation Pit Excavation On The Surrounding Environment

With the rapid development of chinese economy,provincial capitals and developde cities in China join the team of metro construction.Metro station foundation pit excavation has greater impact for surrounding environment as the big excavation area and deep excavation depth.This paper according to the data of metro foundation pit excavation in Changchun,use MIDAS GTS NX finite element software simulating the process of foundation pit excavation.Researching the influence for surrounding environment of foundation pit excavation.The main research contents and conclusions are as follows:(1)Expound the research status of the influence for surrounding environment of foundation pit excavation in theory and numerical simulation.(2)Summarizes the theory of influence for surrounding environment of foundation pit excavation,include deformation of supporting structures,bottom heave,ground settlement around foundation pit.Introduce the calculation method of horizontal displacement of supporting structures,bottom heave,ground settlement around foundation pit.(3)Analysis and arrange the monitoring data of foundation pit,summarizes the change law of ground settlement around foundation pit,lateral wall deflection,bottom heave.(1)After the foundation pit,the surface behind diaphragm retaining walls appear settlement.At first,the settlement increases then decreases as increasing distance,the settlement become the shape of right.(2)The diaphragm retaining wall appear horizontal displacement,the distribution of lateral wall deflection present small between the two sides.(3)the distribution of bottom heave present small between the two sides.(4)Introduce the step of the MIDAS GTS NX software bulid models,and compare the monitoring data with the simulated data,validate the accuracy of constitutive model and related parameters.(5)Do the simulation after change the depth and thickness of diaphragm retaining wall in the model,analyse the influence for surrounding environment of foundation pit excavation in the case of changing the condition of the support.The result of analysis:The maximum surface settlement behind diaphragm retaining walls reduce 64% and the maximum lateral wall deflection reduce 74.62%,the bottom heave reduce only 14.62% when the thickness of diaphragm retaining wall increase from 0.4m to 1.2m.The reduction of maximum surface settlement behind diaphragm retaining walls and bottom heave is very small,the maximum lateral wall deflection almost never changes when the thickness of diaphragm retaining wall increase from1.2m to 2.2m.The maximum surface settlement behind diaphragm retaining walls reduce 43.48% and the maximum lateral wall deflection reduce 55.38%,the bottom heave reduce 56.96% when the depth of diaphragm retaining wall increase from 20 m to 32 m.Keep increasing the depth of diaphragm retaining wall when the depth was32 m,these three kinds of change have little reduction.