Propagating compaction bands in confined compression of snow: Experiment and Modelling

We show that the plastic deformation of snow under uniaxial compression is characterized by complex spatio-temporal strain localization phenomena. Deformation is characterized by repeated nucleation and propagation of compaction bands. Compaction bands are also observed during the very first stage of compression of solid foams where a single band moves across the sample at approximately constant stress. However, snow differs from these materials as repeated nucleation and propagation of bands occurs throughout the subsequent hardening stage until the end of the deformation experiment. Band nucleation and/or reflection of bands at the sample boundaries are accompanied by stress drops which punctuate the stress strain curve. A constitutive model is proposed which quantitatively reproduces all features of this oscillatory deformation mode. To this end, a well-established compressive plasticity framework for solid foams is generalized to account for shear softening behavior, time dependence of microstructure (`rapid sintering') and non-locality of damage processes in snow.