Influence of the loading direction on the uniaxial compressive strength of sea ice based on field measurements

Sea ice is composed of columnar-shaped grains. To investigate the influence of the loading direction on the uniaxial compressive strength and failure processes of sea ice, field experiments were performed with first-year level ice. Loads were applied both horizontally (parallel to the grain columns) and vertically (across the grain columns) with various nominal strain rates. Two failure modes have been observed: a ductile failure mode at low nominal strain rates, and a brittle failure mode at high nominal strain rates. However, the failure pattern of sea ice was clearly dependent on the loading direction. At low nominal strain rates (ductile failure mode), the sea-ice samples yielded due to the development of wing cracks under horizontal loading and due to splaying out at one end under vertical loading. When sea ice fails in the ductile mode, the deformation is driven by grain boundary sliding under horizontal loading and by grain decohesion and crystal deflection under vertical loading. At high nominal strain rates (brittle failure mode), the sea-ice samples failed in shear faulting under horizontal loading and in cross-column buckling under vertical loading. The nominal strain rate at the brittle-ductile transition zone is about ten times higher under vertical loading.