Triaxial tests on snow at low strain rate. Part II. Constitutive behaviour

Abstract

Fine-grained, dry snow with a density range of 190^435kg m^3 was tested in triaxial compression at^12 C with confining pressures varying between 0 and 40 kPa.The tests were strain-rate controlled, with strain rates ranging between 7.4610^7 s^1 and 6.6610^5 s^1. The analysis of the test results revealed that the relationship between yield stress and viscous strain rate is best given by a power law, similar to polycrystalline ice. However, the power-law exponent n is a function of density and varies between 1.8 (low-density snow, » 5 200 kg m^3) and 3.6 (high-density snow, » 4320 kg m^3). The tests also showed that lower-density snow displays a significant non-linear stress^strain response before yielding. Two further aspects of the constitutive behaviour of snow were identified: (1) the strainrate independence of the post-yield work-hardening behaviour in compression and (2) the independence of the axial yield stress in relation to the confining pressure. The experimental observations are discussed with respect to the mechanical properties of polycrystalline ice, which is the constituent material of the load-bearing ice skeleton.

Numerical homogenization of the viscoplastic behavior of snow based on X-ray tomography images

“…However, the uncertainties made on our model parameters should be quantified through a sensitivity analysis in order to reckon the ability of our homogenized law for snow viscosity to quantitatively recover the experimental results of Desrues et al (1980), Bartelt and von Moos (2000), Moos et al (2003) and Scopozza and Bartelt (2003b).…”

“…Within the framework of continuum mechanics, several phenomenological models have then been proposed in order to account for these experimental data (Desrues et al, 1980;Scopozza and Bartelt, 2003b;Cresseri and Jommi, 2005;Navarre et al, 2007;Cresseri et al, 2009). The fitted material parameters arising in these models often only characterize the mean properties of a few types of snow in a restricted density range.…”

Quantification of basal friction for technical and silvicultural glide-snow avalanche mitigation measures

“…Glide-snow avalanches are observed every season on the Dorfberg, above Davos, Switzerland, and were documented via time lapse photography in the winters of /2012/2013(van Herwijnen and Simenhois, 2012. Their occurrence depends on meteorological conditions such as temperature, snow depth, snow stratification and ground temperature (Dreier, 2013;Dreier et al, 2013), but their location in the terrain is almost similar each year.…”

“…Because snow is a visco-elastic material, the stauchwall resisting stress σ is time dependent. A simple Burger model is used to calculate the resisting action of the stauchwall: The visco-elastic constants (E m , E k , η m , η k ) are density and temperature dependent (Von Moos et al, 2003;Scapozza and Bartelt, 2003). Equations (2) and (3) are a system of two coupled ordinary differential equations that can be solved numerically.…”

“…Ground friction dictates the force redistribution and therefore the loading on the stauchwall (In der Gand and Zupančič, 1966;McClung, 1975;Höller, 2004;Bartelt et al, 2012). Vegetation can increase the ground roughness significantly (de Quervain, 1979;Fiebiger, 1978;Newesely et al, 2000;Höller, 2001;Leitinger et al, 2008;Schneebeli and Bebi, 2004;Weir, 2002). Although all authors agree that glidesnow avalanche activity is retarded by dense forest stands, the quantification of basal friction as a function of vegetation structure is missing.…”