The Use of Gabbro Rock Armour in Rubble Mound Structures

Throughout several years Gabbro rocks have been used for various coast protective constructions and breakwaters at the North Sea Coast and in inner Danish waters. So far the use of Gabbro has been based solely on calculations from Shore Protection Manuals, i.e without model tests. Compared to ordinary
granite breakwaters the smaller Gabbro constructions have proved to be very competitive. The Gabbro constructions are more stable and the smaller units makes it possible to use smaller equipment. The choice of rocks is normally based on the consultant's calculations compared to the most favorable offer. In order to exploit the advantages of Gabbro, Franzefoss Bruk, Norway; Havnecon Consulting Aps and the Aalborg University, Denmark have entered a co-operation on the development of a Gabbro rubble mound breakwater.
This paper describes the development of the project and explains the savings obtained by using Gabbro instead of ordinary granite.