An explanatory model for failure modes of compacted snow under uniaxial compression

Uniaxial compression is a primary method for testing compacted snow structures. However, previous categorizations and explanatory models for the diverse failure modes of compacted snow under uniaxial displacement-controlled compression are not completely compatible with observed experimental phenomena. This study distinguishes failure during compression into local and non-local types rather than treating the snow specimen as a whole element. Three components of the compressive stress-strain response of compacted snow cylinders, which exhibit highly variable failure modes, are proposed: fracture force, direct contact force, and pseudo-contact force. As the loading rate increases, the relative contributions of these forces shift, with contact forces becoming more dominant. Then, layered compacted snow cylinders were prepared and compressed to substantiate the proposed explanation and to investigate the effect of weak parts in compacted snow specimens on failure modes, strength and deformation properties. As an application of the new explanatory model, some photos of unlayered compacted snow specimens during compression are presented to exemplify the alternating features of the three resistance components under compression. It is found that weak layers in snow cylinders, commonly hidden in in situ coring, would lead to unrepresentative strength and modulus of deformation values, as well as atypical failure modes showing more irregular mixtures and transitions. Based on these findings, this study suggests refinements for prospective in situ testing of compacted snow structures, including additional constraints on compressive strength determination and a preference for loading rate over strain rate as the primary factor in controlling the compressive loading regime.