Modeling ice block failure within drift ice and ice rubble

A major challenge within material science is the proper modeling of force transmission through fragmenting materials under compression. A particularly demanding material is sea ice, which on small scales is an anisotropic material with quasibrittle characteristics under failure. Here we use the particle-based model HiDEM and laboratory-scale experiments on saline ice to develop a material model for fragmenting ice. The material behavior of the HiDEM model-ice, and the experiments are compatible on force transmission and fragmentation if: (i) the typical HiDEM glacier-scale particle size of meters is brought down to millimeters corresponding to the grain size of the laboratory ice, (ii) the often used HiDEM lattice structure is replaced by a planar random structure with an anisotropy in the direction normal to the randomized plane, and (iii) the instant tensile and bending failure criterion, used in HiDEM on glacier scale, is replaced by a cohesive softening failure potential for energy dissipation. The main outcomes of this exercise is that many of the, more or less, traditional ice modeling schemes are proven to be incomplete. In particular, local crushing of ice is not valid as a generic failure mode for fragmented ice under compression. Rather, shear failure, as described by Mohr-Coulomb theory is demonstrated to be the dominant failure mode.