Item: The width of unconfined slab avalanches based on field measurements of slab properties
Title: The width of unconfined slab avalanches based on field measurements of slab properties
Proceedings: 1990 International Snow Science Workshop, Bigfork, Montana USA, October 9-13
Authors: J.B. Jamieson and C.D. Johnstonl
Abstract: Using principles of fracture mechanics, a linear elastic model of an unconfined dry slab and simplifying assumptions, expressions are derived for the energy release rate and for the fracture resistance during the propagation of the rapid brittle fractures which release slab avalanches. The simplified energy release rate is constant as the fractures advance whereas the fracture resistance increases as the fractures spread across the slope. The arrest criterion equates the release rate to the resistance and gives an expression for the width of unconfined slab avalanches in terms of two empirical constants and three field measurements, namely the tensile strength of the slab, the slab density and the inclination of the starting zone. The empirical constants are evaluated by regressing the expression for the width of unconfined slab avalanches on data obtained from measurements made at 13 strictly unconfined slab avalanches during the winters of 1988 and 1989 in the Rocky Mountains of Western Canada. The significant correlation coefficient (0.81) suggests that the expression may provide a quantitative approach to forecasting the width of unconfined slab avalanches.
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Keywords: field measurements, fracture mechanics, starting zone
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