Determination of pullout capacity for an inclined single-plate helical pile under combined loading in clay

Abstract

Although helical piles are frequently installed at an angle to the vertical, there has been limited investigation into how this inclination affects the pile’s ability to resist pullout forces. This paper utilizes numerical analysis to examine the pullout capacities and failure envelopes of inclined helical piles under combined loading. Through the application of the coupled Eulerian-Lagrangian finite element analysis, the impact of load inclination and azimuth angle of the pullout plane on the ultimate holding capacity of inclined helical piles was assessed. It was found that the pullout plane that is in the opposite direction to the helical pile inclination is the most crucial. The parametric study showed that the crucial failure envelope is primarily influenced by the helical pile inclination angle, embedment depth ratio, helix diameter ratio, and normalized soil strength ratio. Several tables were provided, which contain fitting constants suitable for a range of helical pile inclination angles, embedment depth, helix diameter ratio, and normalized soil strength ratios. Based on these results, a straightforward design procedure was established to evaluate the holding capacity of an inclined installed helical pile. The research results are expected to assist engineers in accounting for helical pile inclination during the design phase.