Research On Stability And Deformation Analysis Of Composite Soil-Nailing In Soft Clay Foundation Pit

Composite soil-nailing is a new supporting form of foundation pit and slope,which is developed from soil nailing.In recent years,it is widely used in the hard-soil firstly,and in the loose-soft soil and the area full of underground water successively.There are a lot of successful engineering example,while some failed projects and accident,the reason of which is complicated and should be exampled from many parts.It is important that its theories stydy are lagging behind the engineering practice. So,in this thesis,with regard to the stability and deformation of composite soil-nailing in soft clay foundation pit, the studies listed below were carried out, considering current research and design status of the soil nailed retaining structure. 1 Based on the use of leading pile with soil nailing protection, studied the work mechanism of mini-pile(wood pile or steel tube) with composite soil-nailing, the model of stability analysis of the composite soil-nailing is established and examined by analysis engineering case. Furthermore, strength reduction FEM is used to examined the stability computation by critical equilibrium method ,and the results tally approximately.It shows that FEM is not only used to the deformation or stress problems,and that composite soil-nailing is used in soft clay is feasible,but the problem is complicated the all-around research must be gone on. 2 According to the constructional feature of the constitution of the leading pile with soil nailing protection, the computation FEM mode is set up to analyze the deformation of the composite soil-nailing when it is stressed. Based on engineering data, using the FEM program PLAXIS, the composite soil-nailing protection is analysed.Furthermore,Deforemation properties of the leading piles with composited soil nailing excavation is studied,such as horizontal displacement,vertical displacement , axial forces of nails,and displacement of leading piles,etc.Compared with the properties of soil nailing protection on the same condition,effect and deformation properties of leading piles with soil nailing protection in soft clay is summarized. 3 In contrast of the structure behaviors in the staged excavation between the soil nailing and the composed soil nailing and with the analysis of various effecting factors on the deformation of composed soil nailing, the thesis holds a analysis of the mechanism's essence of the composed soil nailing. Suggestion on the design and computation of the composed soil nailing is extracted. 4 Generally analyzing,some problems is found that theoretical calculation result is not according to the engineering phenomena,such as the relation with the space length of soil nail(archorage pipe) and horizontal deformation,the relation with the depth of leading(mini) pile and horizontal deformation and vertical deformation.Which result to these problems,compution theory,model,method or the accidents of engineering phenomena,should be kept on researching.