System reliability analysis of soil slopes stabilized with piles

Piles are widely used to increase the stability of piles. Probabilistic methods can be used to explicitly consider the uncertainties involved in a slope stability analysis. Currently, most probabilistic slope stability analyses focus on the reliability of slopes without reinforcement. In this paper, an existing method for system reliability analysis of unreinforced slopes is extended to slopes reinforced with piles. The described procedure may potentially be used to convert other methods for reliability analysis of slopes without reinforcement to slopes reinforced with piles. Two examples are used to illustrate the suggested method. It is found that the location of the most critical slip surface of the reinforced slope generally differs from that of the unreinforced slope, and may change with the pile location and the pile spacing. The optimal locations of the piles with and without considering the uncertainties in the soil property are different. For slopes in layered soils, the system failure probability may be governed by several representative slip surfaces even when piles are installed. The system effect is more obvious when the pile spacing increases. To maximize the effectiveness of slope stabilization, the stabilizing piles should intersect with all representative slip surfaces with significant failure probabilities.