Research On Retaining Mechanism And Accident Of Soil Nailing In Excavation

With the continuous developments of the urban construction, the springing up of the high buildings and the opening up of the underground space, the deep excavation project is increasing greatly. As an effective retaining technique, soil nailing is widely used for its quickly construction and low cost. However, there are still many accidents occurring in excavation of soil nailing. Therefore, it is significant to make further studies on soil nailing.In this thesis, the development of soil nailing and its definition, classifications and scope for application are summarized and illustrated. The differences between soil nailing and traditional bracing techniques of foundation pit are compared, and the development of composite soil nailing technique is introduced.Secondly, the work mechanism and the shear strength between soil and nail as well as the action of water to soil are studied. Based on the available soil nailing cases and relevant computations, the development laws of horizontal displacement and tensile force of soil nails, the failure configurations, the stability of slope and its analysis methods are summarized. Further more, through the investigations and analyses for the process and treatment of some typical accidents of soil nailing, including the one occurred in soft soil foundation pit, the one induced by the action of water, the one happened in composite soil nailing, and the one caused by multiple factors, it is shown that the incorrect exploration, design, construction and the action of water to soil are the main factors leading to accidents of soil nailing.Finally, the proper principle and method in exploration, design, construction and monitoring of soil nailing to avoid accident of soil nailing are proposed. The concrete method to prevent the accident concerned with the action of water to soil is also proposed.