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|A Laboratory investigation of the mechanics and hydraulics of river ice jams
|National Science Foundation (U.S.)
Iowa Institute of Hydraulic Research.
Lee, C. L.
Wang, T. P.
Kennedy, J. F. (John Fisher), 1933-
Ice cover compressive properties
Ice jam thickness
River ice jams
|Cold Regions Research and Engineering Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
|CRREL report ; 77-9.
Abstract: This report presents experimental results on the conditions of initiation of an ice jam by a simple surface obstruction, on the equilibrium thickness of an ice jam formed by accumulation and submergence of ice floes, and on the compressive strength of a floating, fragmented ice cover. In the study on ice jam initiation, it was found that the minimum concentration of floes in the opening of the obstruction at which a jam occurs is nearly independent of the ratio of width of constricted passage to channel width and is proportional to a negative power of the ratio of floe length to width of constricted passage. The coefficient of proportionality and the negative exponent of this power function appear to be dependent upon the ratio of floe length to floe thickness and to be strongly affected by the properties of the material of the laboratory floes, in particular by the interparticle friction or cohesive characteristics. From energy analysis of floe submergence, a relationship between the thickness of a jam formed by accumulation and submergence of floes and the approach flow characteristics was derived and found to fit the experimental data satisfactorily. The relationship predicts that a stable jam cannot be formed when the approach flow velocity exceeds a certain value. This phenomenon was observed experimentally, and the measured maximum values of approach velocity were found to be in excellent agreement with the predicted values. In both studies on jam initiation and development, it was found that surface tension, and therefore the wetting properties of the material used for small laboratory floes, have a significant effect on the submergence velocity of small floes, and should be taken into consideration when small-scale laboratory investigations of ice jam phenomena are conducted using floes made of artificial material. Experiments on compressive strength of floating, fragmented ice covers were conducted for ranges of cover length and cover thickness, using three different floe shapes and sizes. It was found that the compressive strength was inversely proportional to compression velocity and independent of cover length. The effect of cover thickness and floe shape or size remains unclear partly because of the limited ranges of thickness and floe size investigated and partly because of the experimental scatter in the results.
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