Experimental study on performance and enhanced methods of helical piles using Frustum Confining Vessel in Anzali Sand

Abstract

Recently, helical piles have been recognized as a viable alternative to conventional piles, particularly in marine environments. The main issue is soil disturbance during installation and solutions to mitigate impacts and enhance performance. The load-displacement of helical piles with varying geometries is examined to find the best geometry in Anzali Sand. The tested helical piles included 1 to 3 helices, 60- and 90-mm diameters, spacing ratios of 1.5 and 3, and embedded length of 750-mm. Three alternatives are proposed: conical helical, tapered, and post-grouted. Overall, 28 pullout and compression tests were conducted on 14 piles using the Frustum Confining Vessel (FCV) device. Increase in the helix space ratio and number has resulted in greater compression capacity, while an increase in the spacing ratio has led to a decrease in pullout capacity. The torque required for conical and tapered helical piles increased by 18%. However, their compression capacity increased by 20%. Additionally, the pullout capacity of conical and post-grouted piles increased compared to typical helical piles. Finally, piles were compared from various geotechnical and practical perspectives, including cost, bearing capacity, manufacture, and installation torque. Conical and post-grouted helical piles exhibit superior performance compared to the others based on the appraisal.