Field Experiments on Shear Strength of Solid and Freeze-Bonded Sea Ice

Abstract

Sea ice rubble/ridge strength and interaction mechanics are highly important in the design of structures and subsea infrastructure for ice prone offshore environments. To better characterize sea ice conditions in northern Newfoundland, a series of field tests were conducted on landfast ice in Pistolet Bay, NL in February 2018. This paper presents a summary of recent shear strength tests on solid and freeze-bonded ice specimens, to help improve understanding of ice rubble properties and behaviour under field conditions. Both horizontal and vertical sea ice samples were tested under dry and submerged conditions, as well as freeze-bonded ice samples under submerged conditions. Sea ice samples were sheared using the Asymmetric Four Point Bending (AFPB) method, which has been shown to produce a near pure shear region at the center of the specimen. For the dry tests, cores were sheared directly after collection so as to test them in conditions as close to in-situ as possible. For submerged tests, cores were submerged for a specific period of time before shearing. Freeze-bonded samples were prepared using a confinement frame which applied a pressure of 25 kPa to the specimens during submergence. These data for AFPB field tests are an important consideration in modelling the strength of ice rubble/ridges and are the first of their kind. From this work it may be concluded that the AFPB method is a promising approach for studying shear strength of both solid and freeze-bonded specimens in the field and additional testing is recommended. New field testing approaches, such as the one presented here, will help improve understanding of in-situ sea ice properties and behavior, which ultimately supports the development of new ice-structure interaction models, which directly benefits oil and gas, shipping, renewable energy, and public works projects in ice prone Arctic and Sub-Arctic regions.