Robust optimization of stabilizing piles for landslides composed of soil–rock mixtures

Colluvial landslides are mainly composed of soil–rock mixtures with complex composition and structure, resulting in large uncertainties in mechanical properties. This leads to difficulties in designing stabilizing piles for colluvial landslides. In this study, we derive a predictive model for the ultimate lateral force of stabilizing piles in soil–rock mixtures, and use it to evaluate the factor of safety of a pile-stabilized colluvial landslide. Subsequently, robust geotechnical design is employed to optimize the design of the stabilizing piles. The design robustness is measured by the variation of failure probability, an approach which can overcome difficulties in characterizing uncertainties in soil–rock mixture mechanical properties. Accordingly, we propose a robust design procedure for stabilizing piles for colluvial landslides. The design method and procedure are illustrated using a real colluvial landslide case study, out of which the most preferred design considering the safety, cost, and design robustness is obtained. Moreover, the influences of rock blocks and safety requirements on the optimal designs are discussed. Our results show that the angle of repose of the rock blocks and the volumetric block proportion determine whether the mechanical parameters of the soil matrix can be used to effectively design the stabilizing pile. It is also found that a higher safety requirement can improve the design robustness, but at higher cost. The advantages of the proposed method are illustrated by a comparison with the traditional reliability-based design method.