Author(s): S. F. Daly; D. M. Stewart
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Abstract: The force distribution resulting from a floating fragmented ice cover has only been partially examined by previous investigators. Experimental work conducted in CRREL's refrigerated flume facility has examined the two-dimensional force distribution of a floating fragmented ice cover restrained by a boom in a simulated river channel. To determine the force distribution a vertically walled channel, instrumented for measuring normal and tangential forces, and an instrumented restraining boom were installed in a 36.5 m by 1.2 m flume. Two sizes of polyethylene blocks and two similar sizes of freshwater ice blocks were tested using water velocities ranging from 10 to 30 cm/s. The leveling off of forces measured at the instrumented boom with increasing cover length was clearly demonstrated and was substantially in agreement with earlier work. The contribution of the increasing shear forces developed along the shorelines to this leveling off in the data was clearly evident. The coefficient definition, p, between the instrumented shoreline and the fragmented ice cover, was determined. An order of magnitude difference was found between the shear coefficient values of the polyethylene blocks, which averaged 0.43, and the freshwater ice, which averaged 0.044. The normal force measured along the instrumented shoreline could not be related simply by a "K" coefficient (such as Janssen's coefficient) to the longitudinal force as postulated by earlier investigators. Rather, an expression of the form fn = Kf + Co was required, where Co is a function of the cover thickness and is independent of the undercover shear stress or cover length.
Year: 1981