Advanced Method for Improving Verticality of Dynamically Installed Anchors during Free Fall in Water

Abstract

The verticality of a dynamically installed anchor (DIA) during free fall in water is vital for successful installation of the anchor within the seabed. Two lines, a deployment line and a mooring chain, are usually used to install a DIA. The mooring chain is prereleased to the seabed surface, presenting a catenary profile in the seawater. When the anchor is released and falls freely in the seawater, the verticality of the anchor is affected by the tension on the pad eye resulting from the connected mooring chain. Therefore, a vertically hanging arrangement method for the mooring chain is proposed, which is effective in reducing the tilt angle of the anchor during free fall in water compared with the traditional catenary arrangement method. Model tests are subsequently designed to justify the effectivity of the vertical-hanging arrangement of the mooring chain. Finally, a theoretical framework is established to predict not only the fall velocity but also the tilt angle of the DIA during free fall in water, with the deployment line and mooring chain taken into consideration.