Laboratory study on the sliding resistance of level ice and rubble on sand

An experimental set-up was constructed to study the friction behaviour of level ice and ice rubble on different seabeds at large scale and realistic stress levels. This paper presents the results of loading on a sand seabed. The tests were performed with a 4 m2 footprint with vertical stress levels up to 17 kPa. The ice was moved horizontally a distance of about 120 mm with displacement rates from 0.003 to 0.342 mm/s. Four position transducers measured vertical displacements. A total of 47 tests were conducted with level ice and another 24 with ice rubble. Friction coefficients of 0.47 and 0.39 for peak and steady shear stresses, respectively, were obtained with level ice. Those produced with ice rubble were 0.65 and 0.62 for the peak and steady shear resistance, respectively, which represents an increase of about 50% in shear resistance compared with level ice. Shear failure is believed to have occurred at the ice–sediment interface, although the sand's internal friction may have been fully mobilized by the ice rubble. Sediment freeze-up caused a substantial increase in sliding resistance. During this process, the failure plane is believed to have migrated downward and laterally along the freezing front, into the sand bed, with a concurrent increase in shear resistance up to levels comparable to the sand's internal friction. Sand compaction may have contributed also in increasing sliding resistance. These results may be useful for the design of spray ice pads and to assess the stability of grounded ice features.