Abstract

Suction Embedded Plate Anchors (SEPLA) are used increasingly in deep water. The keying process of SEPLA is investigated by using discrete element method. The numerical model is validated by the centrifuge model test. The results show there is a strong dependence on loss in embedment with loading eccentricity (e/B), at e/B=1.0 the loss in embedment is almost negligible, whereas at a small e/B the loss of embedment is large; the horizontal displacement of the anchor is far less than its vertical displacement. The loading velocity of keying process has impacts on embedment loss.

Introduction

The research effort, concerning anchoring systems suitable for deep water environments, has been mainly focusing on three sorts of anchors: Suction Embedded Plate Anchors (SEPLA), Vertical Loaded Anchors (VLA) and Suction caissons. The typical configuration of SEPLA is shown in Fig. 1. The common feature of SEPLA system is the utilization of a suction caisson, called follower', to embed an initially vertical plate anchor, typically inserted in a vertical slot at the follower base. When the system has reached the designed penetration depth, the plate anchor mooring line is disengaged from the follower, leaving the follower free to be retrieved and reused for the next installation. At this point, the plate anchor is embedded vertically in the seabed and mooring line attached to the embedded plate anchor is tensioned, causing the plate anchor to rotate or key' to the designed orientation that is perpendicular to the direction of mooring line. The concept of SEPLA (Dove et al., 1998), including installation and keying stages, is shown schematically in Fig. 2.

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