Measurements of localized dynamic loading in a mountain snow cover

In the majority of fatal avalanches, skiers and snowmobilers apply load to the snow cover which triggers the initial failure in a weak layer. Understanding how the stress due to the dynamic surface load transmits through the snow cover can help people avoid situations where they can trigger avalanches. Capacitive sensors were used to measure this stress within the mountain snow cover. The three main variables affecting stress transmission through the snow cover investigated in this paper are the type of loading, depth and snow cover stratigraphy. At specific depths, snowmobiles added more stress than skiers did, thus increasing the probability of initiating a fracture in a weak layer and releasing a slab avalanche. The increased penetration depth of snowmobiles into the snow cover compared to skiers was the primary reason for this increase in stress. A decrease in stress was observed with increasing depth. A decrease in stress was observed with increased snow cover hardness. Supportive surface layers created a ‘bridging effect’ that spread stress out laterally and decreased the depth to which it penetrated.