Rock glaciers, fault gouge and asphalt: Hard particles in a nonlinear creeping matrix

Composite materials that are composed of hard particles within a soft matrix demonstrate two significantly different deformation behaviours. There is a threshold at which the particle interaction of the hard particles becomes the dominating process. For a low volumetric content of the hard particles, the strain rate of the composite is equal to the strain rate of the soft material reduced by a factor that is a linear function of the volume fraction of the hard particles f. The factor is thought to be material dependent. A value of 1 − (5/3)f was found for the frozen soil under investigation. At large solids fractions creep deformatins are mostly eliminated by dilatancy. Due to the limited tensile strength of the pore ice, the large strain strength of the composite only depends on the strength of the unfrozen soil.