Uplift capacity of the helical anchor installed in cohesionless soil using energy balance approach

Helical anchors are being considered an efficient alternative in offshore applications due to their advantages of being rapid, easy, and inexpensive to install. Hydraulic motors apply torque to the upper end of the screw shaft during installation. Therefore, the most important parameter to be considered during installation is the applied torque. When installing helical anchors, the uplift capacity can be estimated by knowing the torque or vice versa. Because the uncertainty of helical anchor failure mechanisms makes estimating the uplift capacity of helical anchors difficult, few theoretical studies that directly correlate uplift capacity with installation torque have been published. The aim of this study is to develop a theoretical model that describes the relationship between the uplift capacity and installation torque of helical anchors installed in sand. This model is based on an energy balance between the external work applied to the anchor during the installation process and energy dissipation due to the combined effects of penetration and frictional resistance. The research demonstrates that final installation torque, helical anchor geometry, blade pitch, soil characteristics, and helical anchor displacement all have a major role in the uplift capacity. This theoretical model's results agree well with several previous experimental and theoretical findings.