3-D Elastic-Plastic Finite Element Analysis Of Internal Forces And Deformation Of Composite Soil-Nailing Based On Deep Excavation Process

Composite soil nailing technology is a compound supporting technology, in which the soil body is reinforced by soil nailing or soil nailing with other supporting technology. In recent years, with the development of excavation supporting engineering of city building, this technology has become a special soil nailing supporting technology. For different site and geological conditions, it can adopt different composite supporting structure, which has the advantages of flexibility and considering local conditions. That overcomes the inherent shortcomings of traditional soil nailing technology, and has broad application prospects. The technology includes many kinds of structure types, the major study project in this paper is three kinds of composite soil nailing technology including pure soil nailing and soil nailing + prestressed anchor, soil nailing + mixing pile +soil nailing.The comprehensive analysis and testing is carried out for excavation composite soil nailing supporting structure by the establishment of finite element model, numerical calculation and comparative analysis for calculating results. The internal forces and the deformation characteristics in whole process of excavating and supporting of excavation are further revealed, which can provide better scientific basis for the wider application of this supporting technology in home and abroad. The study work is as follows:(1) The formation, the development and the current research present situation of composite soil nail technology are discussed. The advantages, the development survey and the application prospect are comprehensively described. In additional, the problems in the current research are analyzed.(2) According to the characteristics of composite soil nailing supporting technology,based on the full analysis of working mechanism of all parts of the composite soil nailing supporting structure, the 3D finite element model is established by applying finite element analysis software known as ADINA. In view of the construction characteristics of composite soil nailing supporting, the construction process of excavating and supporting for deep excavation is simulated. Taking a deep excavation as example, the simulation and analysis are carried out respectively correspondingly to three different supporting types, namely the pure soil nails, the soil nailing + prestressed anchor and the soil nailing + mixing pile + soil nailing. Then the simulating results including the internal forces, thedisplacements and the deformations are obtained on the condition of three supporting methods.(3) Based on the above finite element simulation, the influence of each working performance parameter on the performance of composite soil nailing supporting is analyzed, in which the parameters include soil nail length, soil nailing inclination, embedded depth and rigidity of mixing pile and so on. The influencing law of the changes of these parameters to the effect adopting composite soil nailing supporting is discussed.(4) The dynamic responses of pure soil nailing and composite soil nailing supporting structure are analyzed under the act of earthquake. Finally, the change law of axial force of soil nails and response acceleration and dynamical displacement of supporting structure are numerically simulated under the act of the United States EL-Centre earthquake wave and Lanzhou artificial earthquake wave.