| When a slab avalanche is triggered, the weak layer and all sides of the slab (crown, flank, and stauchwall) are fractured. Wet slab avalanches frequently involve thick, strong slabs. At present, the stability index is defined as the ratio of the strength of the weak layer to the stress induced by the slab weight; we think that this index underestimates stability, especially in warm heavy-snow regions such as those in central Japan. For more realistic stability evaluation of wet slab avalanches, we propose a stability index that considers the slab strength.To estimate the slab strength, slabs are classified into three size-based groups: 10 m × 10 m, 50 m × 50 m, 100 m × 100 m. Furthermore, the slab states are classified into four types depending on the effective part of the slab acting as support: wcfs (weak layer, crown, flank, and stauchwall), wcf (weak layer, crown, and flank),wfs (weak layer, flank, and stauchwall), and wf (weak layer and flank). The results of our test calculation suggest that the slab strength should not be disregarded when evaluating stability, especially for small, high-density slabs. We believe that the proposed stability index will be useful in avalanche safety operations because it can lower the false alarm rate by considering the slab size and effective part of the slab. |
