Laboratory experiments on floating saline ice block breakage in ice-to-ice contact

Abstract

This study uses a unique experimental system to explore the breakage of laboratory-grown, floating saline ice blocks under ice-to-ice contacts. This topic is important to the understanding and modeling of force transmission through ice rubble fields. In a collection of ice blocks subjected to compressive loading, force is transmitted via force chains, and their stability plays a crucial role in ice-structure interaction processes. Peak loads are limited by the buckling of these force chains or breakage at the ice block contacts. Lack of information on the breakage mechanism motivates the present effort. In the experiments, three ice blocks were set up to form two ice-to-ice contacts, after which the three-block system was compressed to failure. The force transmitted through each contact and the failure process of the blocks were recorded. In total 32 tests with varying contact areas were performed. In about 75% of the cases, the load transmitted by an ice-to-ice contact was limited by shear failure. The key property limiting the magnitude of the force transmitted by an ice-to-ice contact was found to be shear strength; blocks typically failed in shear on planes having the characteristics of ‘Coulombic shear faults’. Quasi-static force equilibrium analysis of these shear failures showed that the floating ice blocks with a naturally occurring temperature gradient used in this study had a shear strength of 279 kPa. Other failure modes, including crushing, splitting and ‘Y-shaped’ conjugate failure, were occasionally observed.