Force Distribution in a Fragmented Ice Cover

摘要

Experiments were conducted in CRREL's refrigerated flume facility to examine 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 tangetial forces, and an instrumentd restraining boom were installed in a 40.0- by 1.3-m flume. Two sizes of polyethlene blocks and two similar sizes of freshwater ice blocks were tested using water velocities ranging from 10 to 30 cm/s. The forces measured at the instrumented boom leveled off with increasing cover length. The contribution of the increasing shear forces developed along the shorelines to this leveling off in the data was clearly evident. The shear coefficients of the polyethylene blocks averaged 0.43, and the freshwater ice averaged 0.044. The normal force along the instrumented shoreline could not be related simply by a K coefficient to the longitudinal force; another expression was required. with a teerm beig a function of the cover thickness and independent of the undercover shear stress or cover length. By adding this term, good agreement was then found between the measured and predicted values of the boom forces and the shoreline normal and shear forces.