Failure of Snow Slopes

摘要: ABSTRACT Snow is a complex material with unique properties such as high compressibility and thermodynamic instability. It is, therefore, not surprising that the failure mechanisms of avalanche slopes are well understood, in fact, controversial. Observations made starting zone slab avalanches follows: slabs occur almost exclusively on planar slopes, inclined between 30 50° strong peak occurrence at about 40°. The upslope tensile fracture (crown surface) nearly perpendicular to main shear plane (bed surface). side fractures (flanks) tend zigzag downslope, oscillating fractures. Unstable usually consist strong, stiff layer resting weak substratum; thickness varies from less than 1 cm over 10 cm. Computed strength/load ratios evaluated observed bed surfaces have wide variance; some variance may be removed improved in-situ tests. A broad model instability proposed if substratum weak, stress hence elastic energy will increase substantially slab, which becomes primed for fracture. Any disturbance jar already weakened initiate fractures; turn, cooperate drive Thus, propagate catastrophically area before snow can rebond heal weakness.