FRICTION ALONG COULOMBIC SHEAR FAULTS IN FIRST-YEAR ARCTIC SEA ICE

摘要

Coulombic shear faults mark brittle terminal failure of virgin S2 ice when rapidly loaded in across-the-column compression under a moderate degree of confinement, as described by Schulson (2004). Previous experiments (Fortt & Schulson, 2004) have described friction coefficients along Coulombic shear faults in fresh-water S2 ice. This paper compares those fresh-water coefficients to coefficients determined from faults in first-year arctic sea ice. The ice was collected from the Beaufort Sea during April 2003, and Coulombic shear faults were introduced as described by Fortt & Schulson (2004). Biaxial sliding experiments were performed at -10℃ at five sliding velocities (4 x 10~(-3), 8 x 10~(-4), 8 x 10~(-5), 8 x 10~(-6) and 8 x 10~(-7) m/s). It was found that kinetic friction coefficients follow a trend similar to that seen by Fortt & Schulson (2004) in fresh-water ice. Coefficients range from 0.69 ± 0.08 at the lowest velocity, rising to a peak value of 0.79 ± 0.09 at 8 x 10~(-5) m/s and then decreasing to 0.37 ± 0.15 at 4 x 10~(-3) m/s. In comparison, fresh-water coefficients vary from 1.00 at the lowest velocity, rising to 1.04 at 8 x 10~(-6) m/s and then decreasing to 0.39 at 4 x 10~(-3) m/s. Roughness measurements of melted, sanded and faulted surfaces, for both saline and fresh-water ice, revealed that for all velocities, as the roughness increases, so does the kinetic friction coefficient.