Probabilistic analysis of local instability between soil nails

Abstract

The objective of this study was to evaluate the probability of local failure between soil nails using a Monte Carlo simulation. The factor of safety (FoS) against local failure in a slope reinforced with soil nails was calculated based on the limit equilibrium method. Random soil characteristic variables were generated based on their distributions and, in accordance with these variables, the FoS of nailed slopes with various slope angles (40–65°), nail inclinations (0–45°), nail spacings (1–8 m), soil thicknesses (1–10 m) and ground conditions (dry, saturated and seepage conditions) was examined. The results showed that the parameters for nail and ground conditions had an influence on the probability of failure (Pf). The effect of wire mesh was also investigated and the Pf of local failure between nails decreased due to the presence of the wire mesh. It was also found that, to achieve Pf < 0·5 without a wire mesh, in the design of nails considering local failure, the nail spacing should not exceed 1·75, 1·50 and 1·25 m for slope angles of 55, 60 and 65°, respectively. With wire mesh, a nail spacing up to 2 m is permissible for Pf < 0·5.