Development of Rational Method of Design of Soil Nailing System in Granular Soil

Soil Nailing technique involves installation of driven or grouted nails (steel bars) spaced closely down the slope/excavation in stages to create an in-situ coherent gravity structure to increase the shear strength of soil and restrain its movement. Soil nailed wall in granular soils is likely to have rotation about toe and tend to behave as a reinforced earth wall after construction. Hence in the present paper, an attempt is made to design soil nailing system based on classical Rankine’s earth pressure theory (1857) coupling with coherent gravity analysis of reinforced earth wall design in selected granular soil possessing required minimum cohesion of 7 kN/m² for adopting soil nailing technique. The design data generated for soil nailed wall is compared with the existing Gassler design method (1996). Soil nailed walls designed for soil retention in excavations of heights varying from 4.5 to 10 m are compared with the Gassler method-based designs. The proposed design methodology yielded L/H ratios of 0.75–1.1 for different heights of soil nail walls in contrast to the L/H ratios of 0.6–0.7 in Gassler's method.