Large-Scale Experimental Investigation of the Performance of Helical Piles Under Cyclic Lateral Loading in Dense Sand

Helical piles are increasingly used in foundation engineering due to their rapid installation, economic advantages, and superior structural performance. Their applicability to various soil conditions has led to widespread use in both onshore and offshore structures. Therefore, their behavior under vertical and lateral static loads, as well as repeated cyclic loading, must be thoroughly evaluated. Helical piles are installed by applying torque through the helical plates attached to their shafts, causing disturbance in the surrounding sand. The influence of this disturbance on pile load-bearing capacity should not be overlooked. In this study, large-scale laboratory tests were conducted on helical piles with different helix diameters and configurations in dry dense sand. The effects of installation-induced sand disturbance and bidirectional cyclic lateral loading on the lateral and uplift capacities were investigated. The results showed that installation-induced sand disturbance reduced the lateral capacity, whereas increasing the helix diameter significantly enhanced the uplift capacity. After cyclic loading, the lateral and uplift capacities of the straight pile decreased by approximately 35% and 55%, respectively, while the lateral capacity of the helical piles was maintained. These findings highlight the importance of considering installation-induced sand disturbance and cyclic loading in the design of helical piles in dry dense sand.