No abstract

Snow is a porous disordered medium consisting of air and three water phases: ice, vapor, and liquid. The ice phase consists of an assemblage of grains, ice matrix, initially arranged over a random load bearing skeleton. The quantitative relationship between density and morphological characteristics of different snow microstructures is still an open issue. In this work, a three-dimensional fractal description of density corresponding to different snow microstructure is put forward. First, snow density is simulated in terms of a generalized Menger sponge model. Then, a fully three-dimensional compact stochastic fractal model is adopted. The latter approach yields a quantitative map of the randomness of the snow texture, which is described as a three-dimensional fractional Brownian field with the Hurst exponent H varying as continuous parameters. The Hurst exponent is found to be strongly dependent on snow morphology and density. The approach might be applied to all those cases where the morphological evolution of snow cover or ice sheets should be conveniently described at a quantitative level.

Abstract. Natural sintering in ice is a fundamental process determining mechanical properties of various ice forms. According to the literature, limited data are available about the complex subjects of snow sintering and bond formation. Here, through cold laboratory mechanical tests with a new shear apparatus we demonstrate time-dependent effects of isothermal sintering on interface strengthening at various normal pressures. Measurements showed that interfacial strength evolved rapidly, conforming to a power law (mean exponent ≈ 0.21); higher pressure corresponded to higher initial strength and sintering rates. Our findings are consistent with observations on homogeneous snow, provide unique records essential for slope stability models and indicate the significant importance of normal load on data interpretation.

No abstract

On the basis of the evidence of fractality reported in the literature as regards snow material and snow avalanches, the paper introduces a statistical model for the natural release of slab avalanches characterized by the differing cohesion of the snow cover at different scales. Under the hypothesis of scale invariance of shear strength, this model can be used to estimate the stability of snow slopes of different types, and to examine whether defects can propagate from the microscale (cohesion and friction) to the macroscale of the weak plane (big avalanche) or whether they eventually stop at a certain scale (small event). This may shed light on the apparently inexplicable differences in behaviour of snow covers which look macroscopically similar, under the same mechanical loads, and which may eventually trigger an avalanche or not.