Model tests by centrifuge of soil nail reinforcements

Soil nailing is an in situ technique to reinforce slopes in the vadose zone where the soil is partially saturated. In this research, model tests of so il nailing on steep cuttings of an unsaturated silty clay were performed us ing a centrifuge. The results show that soil nailing can greatly increase t he stability of cuttings. The length and density of soil nails have signifi cant effects on the deformation behavior and failure mechanism of the soil- nailed structure. When the ratio between the maximum nail length and the ex cavation depth (L/H) was 0.32 or 0.34, the model slope was unstable with a prototype spacing less than 1.8 m. However, when the LIH ratio was 0.48 or 0.80, the model slope was substantially stable against global failure under the same spacing. External failure occurred in nailed structures with dens ely reinforced shorter nails; the prototype spacing was less than 1.29 m an d the length ratios were 0.32 and 0.34. Internal failure occurred in nailed structures with sparsely reinforced longer nails; the prototype spacing wa s 3.6 m and the length ratio was 1.0. The failure surfaces of the nailed cu ttings were deeper than that of the cutting without reinforcement.