Effect of Embedment Depth and Pullout Angle on the Movement of Model Suction Anchor

Abstract

In the offshore areas, the engineers are adopting modern construction practices with novel offshore foundation technologies to ease the installation process as well reduce the construction cost. Now a days wind power has gained priority as compared to the coal-based power generation. In the offshore, there is a huge scope for generation of wind-based power. The foundations of wind turbines in the offshore can subject loads coming from water waves, current, vibrations and dead loads. The water depth at places where wind turbines are to be installed varies from 20 to 60 m and it leads to huge cost for construction of conventional foundations. In order to overcome the difficulties associated with construction and high costs of installation of foundations, a novel foundation technique named ‘suction anchor foundations’ has evolved in the recent past. It is simple to install and minimizes the cost as well as construction time of the project. In the offshore, mostly sand and soft clay deposits predominantly present.  In this paper, the study carried out on model suction anchors of L/D = 1, 1.5 and 2 in sand bed are discussed. The anchor aspect ratio L/D is defined as it is the ratio between anchor embedment depth to its diameter. The sand bed was prepared in a test tank corresponding to a 40% relative density of sand. In order to study the pullout movement of anchor, the pullout angles considered are 30^o, 45^o, 60^o and 90^o. The model anchors were installed in a prepared sand bed by pumping out the water from inside the anchor with the help of quarter HP centrifugal pump. The results revealed that the anchors pulled with lower pullout angle are taking higher pullout loads to cause a movement in the anchors and it is attributed to enhanced passive resistance from soil. Also, the embedment depth of anchor offered better resistance to movement of anchor.