Chute experiments on slushflow dynamics

Abstract

Slushflows are gravity mass flows consisting of a mixture of snow and water, which exhibit considerable damage potential for endangered areas. Small scale slushflows with a volume of 10-15 m3 were generated in the 30 m long and 2.5 m wide snow chute of the Swiss Federal Institute of Snow and Avalanche Research at Weissfluhjoch, Davos, Switzerland. Velocity profiles, dynamic pressure, basal and normal shear and flow height data were recorded in order to test suitable instruments for slushflow measurements. From the obtained data, the order of magnitude of the drag factor for slushflows interacting with obstacles could be estimated. We give an overview of the experimental setup and discuss experimental problems arising from the specific characteristics of slushflows. First results are presented, which indicate that the drag factor might be considerably higher than the estimates commonly used for dry flowing avalanches. Compared to snow avalanches, shear and normal stresses are generally higher in slushflows. The analysis of shear stress versus normal stress indicates some viscoplastic behavior. The results imply that slushflows have to be considered when choosing design criteria for avalanche protection measures wherever this kind of flows can occur. An increase in both temperature and winter precipitation could lead to more frequent slushflow events implying the need to redesign countermeasures. The results from the chute experiments are discussed with respect to development of numerical models of slushflows and a future adaptation of the optical velocity measurement devices to slushflows.

Meteorology, Topography and Snowpack Conditions causing Two Extreme Mid‐Winter Slush and Wet Slab Avalanche Periods in High Arctic Maritime Svalbard

“…Certain flow features only found in slush avalanche deposits, including flow arms and levées (Figures C, D, E, F), indicate a fluid‐like visco‐plastic granular flow, as observed by Jaedicke et al . () in their chute experiments.…”

“…More recently, studies in Iceland (mid‐winter rain‐on‐snow event; Decaulne and Saemundsson, ) and Spain (Furdada et al ., ) have provided detailed descriptions of slush avalanche events, while Jaedicke et al . () carried out work on slush avalanche dynamics simulations.…”

The theoretical plausibility of central pit crater formation via melt drainage

“…Furthermore, any solid particles present in a melt pool will float in the case of ice in water whereas for rock the solid crystals will sink to the bottom of the melt pool so that in reality, the material draining is only partially molten and has a higher effective viscosity than pure molten rock. Jaedicke et al (2008) found that for a volume fraction of snow particles of 0.6, the effective viscosity of water slush is 67 Pa s. Marsh (1981) found that magma typically stops flowing when the crystal volume fraction exceeds 0.55 which corresponds to a critical viscosity of 10 4.6 Pa s. As expected, these higher viscosities lead to a lower volume of material draining into fractures (see Fig. 9).…”

Predicting Snow Velocity in Large Chute Flows Under Different Environmental Conditions

“…For snow in the coexistence regime of snow and water at 0 • C, snow density and snow water content are typically positively related. High water content causes additional basal friction by lubricationadhesion effects on the ground, especially if the flow is water-dominated, as in slush flows (Jaedicke et al, 2008). Compact (ρ > 300 kg/m 3 ), dry snow exhibits slightly less basal friction on dry ground.…”