Study On The Mechanism And Engineering Application Of Soil Nailing

With the continuous development of the urban construction, the springing up of high-rise buildings and the exploitation of the underground space, the deep excavation project is increasing rapidly. As a new retaining technique developed abroad and used in excavation and slope stabilization, soil nailing has become popular in the excavation project since it was introduced to China in 1980's, not only in the northern hard-soil area but also in the coastal soft soil zone. However, the actual working mechanism of the soil nailing is still unknown, and the theory about soil nailing does not match its application in the engineering.In this thesis, the developing history of soil nailing and its definition, classification, applicability and the open questions are presented. The working mechanism of soil nailing retaining system is also investigated systematically. Based on the analyses of the distribution rule of the horizontal displacement and the stretching force, the failure pattern and the stability analysis methods, the merits and shortcomings as well as the applicability of such kind of retaining structure are summarized. In addition, some technical problems in the construction and monitoring process are discussed.Secondly, the principle, method and specific content of the soil nailing design are introduced in detail. The calculation fundamentals of soil nailing is also analyzed and discussed. Moreover, some remarks on design and calculation are made for the current standard method and finite element method (FEM) related to soil nailing.Finally, a engineering example is given by using both the current standard method and the FEM. The soil deforming in the retaining structure, the ground surface settlement near the foundation ditch and the variation of the internal force of soil nail during the steps of excavation are calculated and analyzed. The retaining mechanism and working performance of soil nailing are further illustrated.The work presented herein can be used as the reference in the soil nailing design and the engineering applications.