Numerical Investigation of Influence of Low Ice Friction on Mobility of Rock-Ice Avalanches

The rising frequency of rock-ice avalanches, related to global climate change, poses a severe challenge to the maintenance of the habitable earth. Compared with ordinary geomaterial, the ice component is characterized by its low friction coefficient, which is well-accepted to be a significant factor for the hypermobility of rock-ice avalanches. The influences of low ice friction on the mobility of rock-ice avalanches remain an open issue. Considering the difficulty in isolating the effect of low friction from that of melting, a numerical investigation with the discrete element method was performed to discuss individually the function of low friction of ice in rock-ice avalanches. Granule flow in a small flume was simulated, considering various factors, including ice content, initial spatial arrangement of gravel and ice particles, and basal friction coefficient. The results revealed an intensively increasing mobility of granule flow with ice content rising and a unique composite moving regime in the case with low basal friction. A difference in deposit morphology was found between ice-underlying and ice-overlying cases i.e., a long-traveled deposit with horizontal gravel-ice particle segregation was found in the former and a short-traveled deposit with vertical gravel-ice particle segregation was found in the latter. This study is expected to be helpful in better understanding the behavior of ordinary geomaterial involving slippery substances, e.g., ice, snow, or firn.