Study of pile configuration for efficient stabilization of clayey slopes using three-dimensional numerical analysis

This study investigated the short-term (undrained) behavior clayey slopes, stabilized with a group of piles, via three-dimensional (3D) finite element analysis. Deformations and stability conditions were investigated considering various soil strength parameters, pile head conditions, and pile spacing-to-diameter ratios, pile group position for slopes with and without surcharge loads. Both full models and slice models were used in this study. Slice models were utilized to evaluate the behavior of stabilized slopes under continuous load and those without surcharge load. Full models were specifically used in slope cases with applied local (finite length and width) loads. The main goal of this research work is to better understand the effects of pile configuration and pile head conditions on the stability of the pile-stabilized slopes to achieve efficient slope stabilization using pile groups. The aim is to gain design insight into the most optimal pile group configuration/configurations which yield higher factor of safety and lower pile head deformations, using the minimum number of piles and concrete volume. For this purpose, various efficiency factors that account for the number of piles were proposed and evaluated for the stability slopes stabilized with pile groups. The results showed that optimization has to be evaluated based on the required level of slope stabilization (the target factor of safety) and the feasibility of changing the location of the piles along the slope or installing more piles or installing a pile cap beam. For the case of locally-loaded slopes, when it is not possible to install more piles, the most efficient solution can be to install a pile group with a pile cap beam in the upper part of the slope. When it is not feasible to construct a pile cap beams due to space restrictions, increasing the rows of piles (installing two or three rows) in the upper part of a locally loaded slope yields a more efficient solution, with an effort to keep the total number of piles the same. This can be done by increasing the pile spacing over pile diameter ratio (S/D) while increasing the rows. The results also show that reducing the S/D ratio is the most economical solution for stabilizing natural slopes with weaker soils.