The surface of concrete structures is subject to abrasion when they are constructed in rivers which freeze over in winter or in sea water where ice movement is active. Abrasion occurs due to the friction force between ice sheets and the structure caused by the ice force working on the structure. Over the past ten yean we have been conducting experiments with many types of concrete and their possible coating materials to find their characteristics of abrasion due to movements of ice sheets with different contents. In recent yean some bridge piers in estuaries have been built with stone faces, and it is conceivable to coat the surface of concrete offshore structures with stone to harmonize the structures with their surrounding landscapes. Thus in this experiment we calculated the abrasion rates (average amount of abrasion per 1 km movement of ice sheets) of various kinds of stone needed to estimate the abrasion amount due to movements of lee sheets, and we also clarified the mechanism of abrasion.
Sea ice is moved by the ocean current, the wind and the tide. This movement generates a frictional force between the surface of structures and sea ice, which causes abrasion of the surface of structures. Therefore, this type of abrasion on the surface of offshore structures deserves close attention when designing them for sea waters which are frozen during winter and where ice floes occur, such as the Okhotsk Sea, Beaufort Sea, Bering Sea and Bothnia Bay. In addition, when constructing bridges over rivers frozen during winter in Hokkaido and in other countries, the abrasion on the upstream side of the surface of bridge piers due to movements of ice sheets in the snow-melting period should be taken into account. This is clearly supported by reports on the abrasion of offshore concrete lighthouses in the Bothnia Bay and river bridges in Hokkaido.
