EXPERIMENTS ON THE RELATION BETWEEN FREEZE- BOND AND ICE RUBBLE STRENGTH, PART I: SHEAR BOX EXPERIMENTS

摘要

The freeze-bond effects on the resistance of floating ice ridges and their deformation process is investigated. The results from 14 shear box tests are presented in this paper (part I) together with a preliminary analyse. Part II gives results from individual freeze-bond tests and a comparison between experimental and numerical shear box tests. The rubble was composed of 60 × 40 × 22 mm saline ice blocks. Freeze-bonds with three different strength levels were created in the rubble by submerging it during 0 min, 10 min and 20 hours. The rubble was tested in a 600 × 600 × 40 mm Plexiglas shear box with vertical confinements of 0.9, 3 and 20 kPa. Observations show that the rubble failure initiates by freeze-bonds breaking. The analyses show that increased freeze-bond strength contributes to higher peak shear stress in the rubble primary failure mode and to the formation of large "block assemblies" when the rubble is breaking. This deformation pattern contributes to an increased dilatation. In the secondary failure mode, the rubble peak shear stress is higher for the tests with the long submersion times, which however present lower freeze bond strength. It is explained by the higher presence of slush between the blocks and the degraded surface of the ice increasing the friction between the blocks.