Three-dimensional Finite Element Analysis For Stability Of Soil Nailing Supporting Engineering

Due to its apparent advantages, soil nailing supporting technique is a type of new supporting structure and widely used in various foundation excavation and slope engineering. In its application, however, some problems have been found. Comparing with its development, the study on its nature and design falls behind. Therefore, the study on soil nailing supporting technique becomes important in foundation excavation. In this thesis, a new supporting structure is introduced. Both the advantages and disadvantages of soil nailing supporting technique are discussed, and the achievements of others are generalized. Then, in ANSYS software environment, a three-dimensional finite element model(FEM) is applied. In the analysis, Drucker-Prager elasto-plastic model is used for soil simulation. The interaction between nails and soil is incorporated. (1) An elasto-plastic strength reduction FEM is used to analyze the stability of the unsupported excavation slope. The safety coefficient is defined on the graph of relation between the horizontal displacement and strength reduction coefficient, and the results are proved by the "Tianhan"software(V2005.1). Some rules and protection emphasis of unstable of the unsupported excavation slope are obtained. (2) A three-dimensional separated finite element model(FEM) is applied to analyze the stability and deformation between nails and soil. In the FEM, the elasto-plastic properties of soil, the interaction between nails and soil, and the construction process are incorporated. The soil, nails and panel which take loads together have the same deformation by rational meshing. Some rules about the stability and deformation of foundation excavation and slope engineering are summarized. A series of suggestions about soil nailing supporting design are introduced. Finally, a practical engineering of the soil nailing supporting in Wuhan is studied. The calculation of FEM is compared with the measured data. The results show that the three-dimensional FEM analysis is effective for stability of soil Nailing Supporting Engineering.