Numerical Value Simulation And Analysis Of Soil Nailing Wall On Bainaohui Foundation Pit Of Changchun

Our country's economy develop fleetly after reform and openingup, meanwhile, it drives fast development of cities. The constructingof a great deal of tall and super tall buildings and the exploitation ofcity planning engineering underground interspace, make the quantityof foundation pit much bigger, and the same as no matter what thedifficulty of technique or the dimensions of foundation fitengineering. The actuality of foundation pit of our country is that:foundation pit is more and more deeper, the conditions of engineeringgeology are more and more bad, buildings around much denser,expenses of retaining and protecting much more. In this condition,the soil nailing wall and the composite soil nailing wall receive greatattention because of it's excellences of economy and high efficiencyin the field of civil engineering.At present,the study of soil nailing wall's action mechanismand stabilization is deficient, it depends on experience andengineering analogy. In this condition , using numerical valuesimulation software ——FlAC2D to research soil nailing wall actionmechanism and it's own stabilization in the process of excavation isvery significative.FLAC2D is a program that can analyze and design civilengineering and mining engineering, it is mostly used to simulateunlinearity of rock,soil and others material, it can solve lots ofcomplicated engineering problems that can't be solved by finityprograms, for example, large distortion , unlinearity andunstabilization system, etc. FLAC2D program uses "mixed dispersed"technique, so it can simulate plasticity breakage and flow exactly,such as large distortion of soil mass arosed by foundation pitexcavation;the difference method does not matrix, so it can save EMSmemory space, reduce operation time, advance solve speed, easy torealize solve the problem of unlinearity and large distortion.FLAC2D4.0 change order operation in the older edition, realize GIICoperation, predigests building model,loading and solving. So, tochoose FLAC2D4.0 to simulate excavation and bracing process isvery reasonable on the theory base and practicality.This paper chooses Mohr-Coulomb elasticity-plasticity moel,adopts FLAC2D program, take Bai Nao Hui foundation pitengineering for calculated example, simulate the process offoundation pit excavation and retaining and protecting, researchdetailedly changing orderliness of aclinic and upright displacement ofsoil mass,the distributing orderliness of soil nailing structure,overloading effect on soil mass and bracing structure, and soil nailing andpile-anchor bracing structure.According to the result of simulate simulation, educeconclusion such as:1,The biggest soil mass aclinic displacement lie on the slopepeak of foundation pit, the value is 25.45mm, it is 2.83‰ of depth offoundation pit, when common soil nailing wall is used. But, themid-underside soil mass aclinic displacement is much bigger, in thesoil nailing and pile-anchor bracing system. It matches with theorderliness of soil nailing wall's displacement in the second chapter.2,The aclinic displacement of foundation pit side increases withexcavating, as well as the velocity of increasement of aclinicdisplacement. So, it is forbad to over excavate, it should be excavatedat the same time it is protected.3,Soil nailing's internal force takes on "bigger on middle part,smaller on end part" along it's all length. but the exterior interiorforce is bigger than end, this is because that the concrete layer passesstrain to soil nailing. Indeed, some soil nailings come forth "biggeron one end, and smaller on the other".4,The axis force on freedom segment of prestressed anchor isinvariable, axis force on fixed segment is degressive. The prestressedforce can improve stress state of soil mass, control availably strain ofsoil mass.5,In the slope feet of foundation pit, it appears stressconvergence, this phenomena illuminates that soil mass yields, it easydestroy.6,The spurted concrete layer suffers pull, and works limitingtympanites,weakening plasticity strain of inter soil mass andstrengthening restriction.7,Under the two bracing form, the vertical displacement isbigger than aclinic displacement, it shows that there is apophysisphenomena on the bottom of foundation pit.8,Over loading on the ground makes aclinic displacementmuch bigger, strain concentrate obviously, yielded area enlarged,and the foundation pit trend to destroy. But, the soil nailing andpile-anchor bracing system can control effectively influence of overloading, enhance security of bracing for foundation pit.