On internal friction and cohesion in unconsolidated ice rubble

Abstract Unconsolidated ice rubble is a mass of ice fragments, often floating in water, that has not solidified by freezing of pore water or by freeze bonding between individual ice-rubble fragments. It is argued herein that unconsolidated ice rubble undergoing continuous shear deformation is essentially cohesionless; i.e., in terms of the Mohr-Coulomb failure criterion, it should not exhibit a cohesive intercept at zero confining pressure and at large shear deformation. Contacting pieces of submerged ice rubble, however, have a propensity to freeze bond with one another, even at very low confining pressures and in nonfrigid air, such that unconsolidated ice rubble may tend to self-solidify. It is this propensity that significantly contributes to the comparatively large values of internal-friction angle that have been reported for ice rubble, and which may cause relationships between shear strength and confining pressure to be nonunique.