Load Transfer Behavior of Multiangle Helical Piles Embedded in Silty Clay under Vertical and Oblique Loads

Multiangle helical piles are used to support multidirectional loads. The load transfer behavior of inclined piles may differ from that of vertical piles. Vertical compressive and oblique uplift load field tests were conducted on a multiangle helical pile group and two single helical piles embedded in silty clay. The load-bearing capacities, group effects, load transfer behavior, earth pressure, and excess pore water pressure were investigated. The results show that the vertical compressive and oblique uplift capacities of the 10°-inclined single helical pile were improved by 12% and 95% compared to those of the vertical single helical pile, respectively. The inclined installation of helical piles significantly optimized the load transfer mechanism of the piles under oblique loads. The group efficiency of the multiangle helical pile group was approximately 102%, attributed to the increased pile spacing resulting from the inclined installation. During loading, the helices and pile toe together contribute more than 50% of the bearing capacities of helical piles. The earth pressure and excess pore water pressure around the grouped helical pile, particularly near the bottom helix, exhibited less variation than those around the single pile, suggesting a smaller disturbance in the surrounding soil.