Discussion on relationship between deformation and stability of soil nailing structure

Because of the advantages such as easy construction, low cost, short construction period and mature construction techniques, soil nailing has been widely used in engineering. However, at present there is lacks of the calculation theory of soil nailing, and shortages also exist in allowable deformation values specified by current specifications. For example, current soil nailing specifications just simply specify an allowable deformation value without considering features of foundation pit, supporting types and surroundings; and these specifications also determine the early warning value for monitoring without combining the deformation with the stability of foundation pits. Thus, these shortages lead to the downward trend of usage of soil nailing that has good performance-price ratio in fact. Based on this, the variable modulus strength reduction method to investigate the relation between deformation and stability of soil nailing is used. After a large number of computational analyses, the comprehensive identification index-deformation-height ratio δh/H is given for deformation and stability of soil nailing. It is found from the computational results that for the same soil and the same stability factor k, the deformation-height ratios of different heights H are nearly the same. Also, the early warning displacement and the maximum allowable displacement are proposed for certain strength and depth of soil nailing structure. Using the tables can determine the early warning displacement and the maximum allowable displacement, which is convenient for engineering application. A specific project proves the reasonableness of these results; and these results can also give reference for deformation early warning values of actual soil nailing structure. This paper could not only determine the deformation of soil nailing structure, but also offer a new method and idea to determine deformation of similar supporting structures, which has some significance for improving the specifications of foundation pits.