Analytic Solution Of Soil-Nail Stress And Its Application

Modern soil nailing technology, as a retaining structure for earth excavation, has been widely used since 1970s due to its convenience and rapidity in construction, economy and reliability. However, because of its complex mechanical behaviors, the design and calculation theory of soil nails lags behind the engineering practice.The key problem in researching mechanical behavior of soil nailing structure is the action mechanism between soil nails and the soil. In this paper, on the basis of present research achievement, the author tries to develop the analytic solution of this problem. The major work and conclusions are as follows:(1) The status of soil nail was distinguished into active tensile and passive tensile. Based on the Mindlin solution of semi-infinite body, and deformation compatibility between the nail and the soil, the differential equation to solve shear stress around soil nail was established.(2) By simplifying expression in the equation with fitting method, the equation was solved readily and the analytic expression of the shear stress along the soil nails is presented. Furthermore, the axial force and displacement of soil nails can be obtained with numerical integral method.(3) For the active state, the characteristics of shear stress distribution of the soil nails under axial load, and the influence of relative stiffness of soil and the nail (E/E_a) on the shear stress distribution along nail were analyzed.(4) For the passive state, the characteristics of shear stress distribution of soil nails subject to excavation release load, the displacement of excavation surface around the soil nails, and the influence of E/E_a on the shear stress distribution were analyzed.Moreover, the results achieved in this paper also can be applied to fully grouted bolt.