| Deep excavations with complicated environment conditions have sprung up during urbanunderground space developing processï¼›these deep excavations are usually surrounded bybuildings and utilities. More severe restrictions are required for these deep excavations. Toensure safety of those adjacent structures and the influence of the ground surface settlementaround of deformation of the supporting structure are needed to be predicted in advance.This isvery important guiding significance about deep foundation pit design and construction in soft soilarea.This thesis carried out researches on the influence of the ground surface settlement aroundof deformation of the supporting structure about deep foundation pit engineering of metro lineNo.10in Nanjing,by means of theoretical analysis,measurement analysis and numericalsimulation.The main work and achievements are as following:(1)According to a contrast and analysis,the simulation results are in accord with measuredresults about the maximum horizontal displacement of wall body,surface subsidence,diaphramwall,and the ground surface settlement curve.Thus the simulation results is feasible.(2)Through the relation research between the horizontal displacement area of wall body ofAqand the ground surface settlement area of Ad, the ratio of Ad/Aqwas different with differentworking conditions.With the increase of excavation depth,the ratio became smaller.At the sametime,it also reflected the surface settlement around with a time lag.The ratio of Ad/Aqlocated at0.4to0.6roughly by quantitative analysis of the conditions.(3) The influence scope of the surface subsidence mainly distributed in the edge of1.5timeseventually excavation depth.The ratio of d/H between0~1.0was the main effect areaï¼›The ratioof d/H between1.0~1.5was secondary influence area.About the ratio of0.5of the d/Happeared the maximum settlement.(4)The affection factors of the deformation of the supporting structure were supplied to thesensitivity of surface subsidence around,including factors of design,construction and soilphysical properties.1)Design factors: With the increasing stiffness of underground continuous wall, thesedimentation value of the vertical surface subsidence around was decreasing, but when the wallrigidity increased to certain degree, increasing wall rigidity to reduce the surface settlement didnot play a significant role.As the buried depth of underground continuous wall increased, theground surface settlement reduced, but meeting the stability of foundation pit request in theembedded depth of solid, adding depth to reduce the ground surface settlement was not obvious.The stiffness and spacing or quantity of the level of support had a great influence on controlingthe deformation of underground continuous wall and reducing the surface settlement around. Compared with the effect of100%and75%design axial force of steel support, the groundsurface settlement was only reduced by4.8%.2)Construction factors: The support time or exposure time after the foundation pitexcavation had a great influence on the ground surface settlement.Compared with immediatesupport,the maximum ground surface settlement of the2days later support inceeased1.5mm,5days later,increasing3.9mm, then it was a trend to speed up.Between the two constructionmethods of"no excavation without support" and "no support without excavation",themaximum ground surface settlement of the former reduced about7.1%.Overloading effected theground surface settlement directlyand sensitively.with increasing overloading value,themaximum surface subsidence also increased gradually.3)Physical properties of soil factors: The modulus of elasticity of soil to effect of surfacesubsidence was very significant.Increasing the soil modulus could effectively reduce the surfacesettlement and control the deformation of foundation pit.When the internal friction angle of soiland the cohesion increased, the surface subsidence reduced.And compared to the cohesion, theinternal friction angle had more effection on the ground surface settlement. |
PDF Full Text Request