Ice-rubble accumulation beneath barges in ice-covered waters

Abstract

This experimentally based study was aimed at determining the equilibrium thicknesses and forms of icerubble accumulations beneath barges moving through ice-covered channels. In addition to significantly increasing the resistance encountered by barges, severe accumulations of ice rubble may cause them to ground and become stuck on channel beds or on exit sills of locks. It is shown that significant amounts of ice may accumulate beneath a barge moving at creeping speed through a navigation channel covered by a sheet of ice, and that accumulation thickness decreases with increasing barge speed. A barge moving slowly through a cover of broken ice, however, may develop a false-bow which deflects ice rubble around the barge such that little ice accumulates beneath it. Increasing barge speed caused more ice to be swept beneath the barge as the false-bow diminishes in size, and eventually a wave-form accumulation develops beneath it. With further increases in speed, accumulation thickness diminishes. An analogy is drawn between icerubble accumulations and sedimentary bedforms in water or air flows.