Arching of Model Ice Floes:Effect of Mixture Variation on Two Block Sizes,

摘要

A study of arching of mixed,square fragmented ice floes at an opening in an ice boom is documented,using results from a model study in which two sizes of plastic blocks represented real ice. A power function,relating the upstream ice concentration to the ratio of a characteristic block dimension to the gap opening,is found adequate to distinguish between arching and nonarching events for block mixtures of two component sizes. It is demonstrated that when the respective total areas of the two block components are nearly equal, a minimum ice concentration initiates an arch across the opening. As the mixture of two sizes of blocks approaches a uniform (one-sized) mixture, a higher concentration of ice is needed to initiate the arch. When the ratio of the block dimension to the gap opening is equal to or less than 0.10,arching of the fragmented ice is not possible,even when the upstream ice discharge exceeds the maximum discharge of ice through a gap opening. The distribution of fragmented ice areas is an important parameter in establishing the minimum size of opening at which an ice boom will retain its arching capability. (Author)