New experiments have been performed on the brittle compressive failure of columnar-grained, first-year sea ice with the S2 growth texture, harvested from the floating cover on the Arctic Ocean. The ice was proportionally loaded biaxially across the columns at –10°C at 1.5 × 10?2 s?1; i.e., within the regime of brittle behavior. The results, when combined with earlier measurements of tensile strength by Richter-Menge and Jones (1993), allow the complete brittle failure envelope to be constructed. The envelope is symmetric about the loading path R = σ 2/σ 1 = 1, owing to the isotropic character of the material within the horizontal plane of the ice sheet, but is asymmetric with respect to the compressive-compressive and tensile-tensile quadrants, owing to the relative weakness of the material under tension. The compressive strength reaches a maximum along the loading path R ～ 0.5. Terminal failure occurs through either splitting (unconfined loading), Coulombic shear faulting under lower confinement (R < 0.2) or spalling under higher confinement (0.2 < R ≤ 1).
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