Kinematic limit analysis of three-dimensional unsaturated soil slopes reinforced with a row of piles

Abstract

Abstract The variation of moisture content in unsaturated soils (i.e., suction) significantly impacts the soil’s strength and is critical in predicting the slope safety. Employing the kinematic limit analysis method, this paper proposes a new method for the stability evaluation of three-dimensional (3D) piled unsaturated soil slopes. A 3D kinematically admissible rotational failure mechanism incorporated with a row of piles is considered and extended to unsaturated conditions. A novel local layer-wise summation method (LLSM) is developed to account for the suction effect on the lateral forces acting on piles. The energy dissipated due to the resistance of anti-slide piles is computed using the LLSM. The proposed method is validated through a series of comparisons with existing results. Numerical studies about the parametric effects were conducted, indicating that the reinforcement of piles depends strongly on the soil types, pile location and pile spacing. The numerical results indicate that the optimum location of piles lies between the middle and top of the slope surface, especially in xp/lx = 0.6–0.7. For gentle unsaturated soil slopes with larger internal friction angles and narrower width constraints, the optimum location of piles approaches the middle of slope surface. The reinforcement of anti-slide piles is more pronounced when the pile spacing D1/dp ≤ 3. The slope stability can be improved by about 10% ~ 20% when the pile spacing D1/dp ≥ 5. Some useful suggestions are presented in this paper for engineering applications.