Experimental investigations of the interaction between sea-ice and berm breakwaters

Abstract

The increasing interest on the Arctic areas has brought us new challenges that have not been met before in other locations due to the peculiarities of these latitudes. In this thesis the interaction between sea-ice and berm breakwaters has been studied. This work introduces new variables to the study of this interaction that have not been reported before, including higher interaction velocities and 3D effects, by varying the ice concentrations and sizes of the ice floes. The other variables tested were the breaking length, thickness and roughness of the ice. To reproduce this interaction, experimental investigations were carried out at NTNU and earlier setups were improved. The ice was modelled with paraffin and pushed against a scaled model of Sirevåg berm breakwater in a flume. The tests were modelled according to Froude scaling law, 1:70. The ice and the breakwater behaviour were analysed and evaluated in relation to the parameters of the ice floes and new findings have been reported. The speed did not have a strong influence on the forces exerted on the breakwater, but it increased the occurrences of ice stacking over the slope and the likeliness of local failures. These local failures invited to reconsider the suitability of no-reshaped berm breakwaters when facing sea-ice. The accretion of ice rubble in front of the breakwater was reported as an effective barrier against the incoming ice. Finally, when introducing the 3D effects with circular ice floes at concentrations around 8/10, the result was always an ice accumulation over the slope of the breakwater, forming ice rubble that protected the structure and did not cause any apparent damage. As a recommendation for further work, improvements should be done to avoid the constraints caused by the flume walls.