Effect of axial stiffness on soil nail forces

Abstract

Currently used soil nail design methods normally ignore axial stiffness of soil nails and assume that nail–soil adhesion fully develops during construction of the soil nail wall, which would allow the use of conventional stability analysis with peak soil parameters for the newly excavated slopes. Although not fully consistent with the monitoring results for soil nails in working conditions, the resulting structures are proven by the accumulated practical experience for conventional geometry and conventional materials used in soil nail construction. This paper considers the effect of axial stiffness on the forces developing in soil nails, which affects the design of soil nails of lower stiffness, for example soil nails reinforced with fibre-reinforced polymer tendons, or nails of greater lengths. The use of fibre-reinforced polymers has considerable advantages in construction due to their light weight, ease of site preparation and high durability. However, their use is often deterred by their relatively low stiffness and lack of ductility. The paper discusses the methods by which negative effect of the use of soil nails of lower axial stiffness and ductility can be overcome in design.