Numerical experiments of soil nails in loose fill slopes subjected to rainfall infiltration effects

Finite difference analyses were conducted to explore the possible behaviour of soil nails in loose fill slopes which were formed by strain-softening materials. Numerical models simulating a 20 m high 35° loose fill slope were set up. With the use of an undrained strain-softening soil model, the behaviour of a loose fill slope reinforced with soil nails subjected to rainfall infiltration was studied. Results indicated that soil nails together with a proper facing structure may reduce the deformation of a loose fill slope caused by rainfall infiltration and hence maintain the stability of the slope. Tensile forces in the soil nails were mobilised through the effective connections between the facing structure and the nail heads when a potential slide was being initiated. Through this mechanism, the development of a flow slide at shallow depths could be avoided by the pull out resistance between the soil and the nails at deeper locations of the slope. Results also showed that, if the soil nails were not connected to a facing structure or nail heads at the slope surface, a global failure mechanism involving the development of a flow slide could be observed, which was similar to that of a loose fill slope without soil nails.