Anticrack Nucleation as Triggering Mechanism for Snow Slab Avalanches
J. Heierli,1,2*
P. Gumbsch,2,3
M. Zaiser1
Snow slab avalanches are believed to begin by the gravity-driven
shear failure of weak layers in stratified snow. The critical
crack length for shear crack propagation along such layers should
increase without bound as the slope decreases. However, recent
experiments show that the critical length of artificially introduced
cracks remains constant or, if anything, slightly decreases
with decreasing slope. This surprising observation can be understood
in terms of volumetric collapse of the weak layer during failure,
resulting in the formation and propagation of mixed-mode anticracks,
which are driven simultaneously by slope-parallel and slope-normal
components of gravity. Such fractures may propagate even if
crack-face friction impedes downhill sliding of the snowpack,
indicating a scenario in which two separate conditions have
to be met for slab avalanche release.
2 Institut für Zuverlässigkeit von Bauteilen und Systemen, Universität Karlsruhe, Kaiserstr. 12, 76131 Karlsruhe, Germany.
3 Fraunhofer Institut für Werkstoffmechanik, Wöhlerstr. 11, 79108 Freiburg, Germany.
* To whom correspondence should be addressed. E-mail: j.heierli{at}ed.ac.uk
