Investigating the effect of helical piles on the load-settlement behavior of a square foundation located over a sandy slope

Helical piles are a type of deep foundation that can resist compressive, tensile, and lateral forces, similar to traditional cylindrical piles. Despite extensive research on their performance on level ground, the specific application and geometric optimization of helical piles for reinforcing foundations situated atop sandy slopes remain underexplored. This study presents a detailed laboratory investigation to evaluate and improve the load-settlement behavior of a square footing located at the edge of a sand slope reinforced with helical piles. A physical model was constructed with a chamber filled with sloping sand, in which helical and cylindrical piles of varying pitches and diameters were installed within the slope. The finite element approach and PLAXIS 3D software employing the hardening soil model were utilized to validate the experimental results. According to the laboratory results, the bearing capacity of a square foundation situated at the edge of a sand slope reinforced with helical piles was up to 142% greater than that of unreinforced slopes and up to 49% greater than that of slopes reinforced with cylindrical piles. Furthermore, augmenting the helix depth, decreasing the spiral pitch, and including the inclined pile enhanced the foundation's bearing capacity by 36%, 23%, and 14%, respectively.