Parametric Study of Pullout Resistance of Anchored Pile Group under Inclined Loading in Dense Sand

Abstract Screw pile foundations are gaining significance in geotechnical engineering due to their rapid installation, high tensile capacity, and effectiveness in supporting structures under uplift loads, like transmission towers and offshore platforms. Despite their extensive use, little is known about how screw pile groups behave under inclined pullout loading. This study investigates the pullout performance of single and double helix pile groups in sandy soil with a relative density 68%, under inclined pullout loads at angles of 10°, 20°, and 45° from horizontal. An experimental program was conducted on groups with spacing (1.5Dh and 4.5Dh) (where Dh is the helix diameter 20mm), the shaft diameter 10 mm and embedded length ratio (L/D = 36) to evaluate the influence of load inclination, number of helix and pile spacing on group inclined pullout capacity. According to the results, when pile spacing increased from (1.5Dh to 4.5Dh), inclined pullout capacity improved by roughly (18 to 30%) because less interactions occurred. Additionally, double-helix piles better than single-helix piles in terms of pullout resistance under all conditions evaluated, with an improvement of 19%. when the inclination angle decreased, the pullout capacity increased. The findings provide useful information for screw pile group design under inclined pullout loads.