Controlling sand placement during the building of artificial islands

Abstract

A new way to construct artificial islands of sand is described. The method shows promise of considerable cost saving. The present high cost of island building is due to the difficulty of making underwater sand slopes steep. Simply dumping sand into the ocean results in slopes of from 12 to 15 horizontal to 1 vertical. These shallow slopes have enormous implications in terms of sand volume and cost. The sand can be tremied into place to form a steep-sided ring or bund. Handling large quantities of sand in this way is expensive. Small-scale model tests show that if the sand is mixed with certain chemicals the resulting 'cohesion' enables the sand to fall through seawater as a block, with little dispersion. Steep underwater slopes result. Low-cost, nontoxic (environmentally safe) chemicals were used in the experiment. Keywords: construction, artificial islands, sand, oceans, dredging.