THE DESIGN OF ANCHOR ELEVATION PLATFORMS FOR CUTTER SUCTION DREDGE D'ARTAGNAN: 'LAST MEN STANDING'

摘要

When dredging hard materials with a cutter suction dredge (CSD), the side wire forces are decisive for production. So in order to dredge efficiently, a high 'holding' force of the side anchors is necessary. Since DEME's new cutter suction dredge d'Artagnan is equipped with the strongest swing winches in the world, they have asked VOSTA LMG to develop, design and manufacture an anchoring system that is capable to meet all the requirements modern dredging vessels nowadays ask for.In general two different working principles of side anchors are used, knowing anchors that dig themselves into the soil. (E.g. Delta, Stevin) and anchors that work on the principle of gravity, or in other words they are kept in place due to their own weight (e.g. box anchors, anchor platforms). For these gravity anchors the simple principle is: the higher the weight, the higher the allowable side wire forces.In case of dredging hard material the gravity type anchors are generally used since conventional anchors can not penetrate (or not deep enough) into the soil anymore. In dredging practice, most of the time simple 'box type anchors' are applied. These are steel boxes with a lot of scrap in it, to which the side wires of the CSD are connected. Lifting and positioning of these boxes is done by means of 'multicats'. Although cheap and simple, both the minimum draft and crane capacity requirements for the multicats increase with increasing anchor weight.An alternative can be found in the use of so-called 'anchor elevation platforms'. These are almost fully self-supporting, can be executed extremely heavy and are still able to work in shallow waters.This paper briefly describes the working principle and history of this concept, followed by a description of the new design. It can be concluded that though the basic concept of the anchor elevation platforms is still the same as it was in the seventies, the new features of the 2006 version make them promising equipment both on an operational level as in transport.