Percolation of freshwater granular ice

Using ice as a model for rock, we experimentally test the prediction of percolation theory that for a sufficiently large sample, the onset of percolation is isotropic even when the crack network is anisotropic. Consistent with theory, experimentally we find that in strongly anisotropic crack networks induced by uniaxial loading at a sufficiently high strain rate, the onset of percolation is nearly isotropic in samples where the dimension of the sample is about an order of magnitude greater than the length of the largest crack. The onset of percolation is isotropic even though nearly 90% of the induced cracks are oriented within about 10° of the direction of applied compression.