Properties of ice from first-year ridges in the Barents Sea and Fram Strait

摘要

First-year ice ridges are one of the main load scenarios that off-shore structures and vessels operating in ice-covered waters have to be designed for. For simulating such load scenarios, the knowledge gap on ice mechanical properties from the consolidated part of first-year ridges has to be filled. In total 410 small-scale uniaxial compression tests were conducted at different strain rates and ice temperatures on ice from the consolidated layer of 6 different first-year ridges in the sea around Svalbard. For the first time uniaxial tensile tests were performed on ice from first-year ridges using a new testing method. Ice strength was evaluated for different ice type, which are determined for each specimen based on a proposed ice classification system for ice from first-year ridges. 78% of all samples contained mixed ice with various compounds of brecciated columnar and granular ice. Ice strength of mixed ice showed isotropy, except for the samples containing mainly columnar ice crystals. For horizontal loading, mixed ice was stronger than columnar and granular ice. The residual strength of ductile ice depended on the strain rate. At 1.5% strain remained 70% of peak strength at 10(-4) s(-1) and 50% at 10(-3) s(-1). Ductile failure dominated for 75% of all mixed ice tests at 10(-3)s(-1) and - 10 degrees C. Ductile compressive strength was generally higher than brittle compressive strength for mixed ice. Brine volume was the main parameter influencing the tensile strength of the mixed ice which was between 0.14 MPa and 0.78 MPa measured at constant ice temperature of - 10 degrees C.