The Optimal Design Of Deep Excavations Soil Nailing Structure Based On Catastrophe Theory

By virtue of its unique superiority, Soil Nailing Way has been rapidly promoted andapplied in China pit engineering. But in the past soil nail retaining design, the quantity ofprojects which adopt the deformation as the control targets is limited, most of them useintensity instead of deformation. In addition, as the theoretical studies of soil nailingtechnique is still far lagging behind the engineering practice in the actual project, especiallythe studies related to the design of displacement calculation. Therefore, it is necessary toresearch the displacement calculation of the structure of the soil nailing further to achieve theneed of providing considerable reference value for the actual project.Firstly, the passive area soil nailing of soil nailing structure is analyzed in this thesis, alsoits potential energy equation is established. The following computation expression of soilnailing ultimate pullout capacity of soil nailing structure is deduced from the catastrophetheory. Then, by using this computation expression and the further stress analysis of soilnailing surface layer, establishing the potential energy equation of the surface layer system,also adopting the minimum potential energy principle, the following analytical expression ofhorizontal critical displacement of the soil outside the foundation pit is deduced.By calculating the actual examples of the works and comparative analysis parameters forthe calculation of a single factor, the conclusions as follow:(1) In order to meet the needs of the project, adjust the inclination of soil nail size is themost economical soil nail design adjustment programs. And the size of soil nail inclination isbetween10°~25°, soil nailing structure for promote stability influence of foundation pit isthe most obvious.(2) Horizontal displacement of soil Foundation Pit slope is the most sensitive forchanges of soil nail diameter, Surface layer thicknessis the secound,and inclination of soilnailis third.(3) The values of control coefficientK cis between2.06~3.76.(4) According to paper’s formula the displacement control inverse deduced soil naildesign parameters calculated and Combined law of Soil nails intensity control and each rowof soil nails in the depth direction of the actual axial force convex distribution (Upper andlower s’ soil nail axial force is small, the central axis force of soil nailing is big) assistant withdesign, In order to achieve a more economical optimization design.