Abstract

Co-authors: Daniel Hatton and Daniel Feltham

We have performed high-resolution double-direct shear friction experiments on saline ice floes in the HSVA environmental test basin. The frictional motion was predominantly stick-slip.  Shear stresses, normal stresses, local strains and slip displacement were measured along the sliding faults, and acoustic emissions were monitored. High resolution measurements during a single stick- slip cycle at several positions along the fault allowed us to identify two phases of frictional slip: a nucleation phase, where a nucleation zone begins to slip before the rest of the fault, and a propagation phase when the entire fault is slipping. We employed a constitutive relation for frictional slip derived from the physics of asperity-asperity contact. We find our experimental data conform reasonably with this frictional law once slip weakening is introduced.  We deduce the interfacial faults failed in the stick-slip cycle through the process of brittle failure of asperities in shear, and at higher velocities, frictional heating, localized surface melting and hydrodynamic lubrication.