Catastrophic air blasts triggered by large ice/rock avalanches

Large ice/rock avalanches have been known to generate extremely powerful air blasts capable of causing fatalities and destruction far beyond the runout of the movement mass. Thus, an appraisal of their possible destructive air blast should be considered during the risk assessments. However, much less is known about how avalanche-induced air blasts occur and how destructive they are. Here an existing DEM-CFD coupled method was innovatively employed to quantitatively analyze the initiation and propagation mechanism of the air blast caused by the largest ice-rock avalanche during Nepal's 2015 Gorkha earthquake, and compared the results with some recorded events. Our results highlighted the contribution of valley morphology to air blast generation. Large high-velocity ice/rock avalanches that have an airborne trajectory or a travel path with turning points can suddenly release tremendous energy and more probably cause destructive air blasts. Additionally, the Langtang air blast presented a propagation of 1 km from the avalanche impact point and equivalent destruction to an EF2-EF5 tornado, causing mass casualties. The large impact region and destructive force of avalanche-induced air blasts suggests their disastrous consequences that should provoke assessment of such type of cascading effect during the landslide risk assessment, especially for the long-term sustainability of planned infrastructure in high-altitude regions.