Laboratory Study of the Helical Piles Behavior Under Reciprocal Loading Via Frustum Confining Vessel (AUT-FCV)

Pile foundations are one of the significant marine substructure systems for a variety of offshore and onshore facilities. In recent years, helical piles have become common foundation system for marine structures exposed to the reciprocal seawater waves. Moreover, these foundation systems have received particular attention due to several influential parameters, including the limited required time for installing and the ability to be immediately loaded after installation. However, the methods for estimating their bearing capacity is limited. The present study investigates the behavior of three different helical piles under tensile and compressive loading via Frustum Confining Vessel available at Amirkabir University of Technology (FCV-AUT). The under-study piles were single, double, and triple-helix with diameters of 70 and 90 mm. Double and triple-helix piles are designed with two different spacing to helix diameter ratios of 1.5 and 3. These piles were installed in Bandar Anzali sand regarding two loose and medium densities. The soil was prepared by adding 4% humidity for testing. The applied bottom pressure of FCV-AUT was 200 kPa. The results indicated that the helical pile bearing capacity increased due to soil improvement and densification during the special installation procedure. However, during the reciprocal loading, the tensile capacity of helical piles was reduced.