Influence of Ice Content on the Run-Out of Rock-Ice Avalanches

Abstract

Rock-ice avalanches in cold high mountain areas can have an extremely high mobility and an enormous destructive potential. As a result of a warming climate, these catastrophic rock-ice avalanches and rock-ice avalanche induced secondary disasters significantly increase and thus have attracted much attention from researchers. Ice is often subject to a critical role to enhance the mobility of rock-ice avalanches. However, the role of ice during the propagation process of rock-ice avalanches has not been systematically investigated and its influencing mechanism on the typically extremely long run-out of such events is poorly understood. In this paper, a series of small flume tests was carried out to simulate the propagation process of rock-ice avalanches and to quantify the influence of ice content on the run-out of such events. Experimental results show that ice particles were involved in the front mass of mixtures of rock and ice particles during their whole movement. The involved granular ice significantly enhanced the mobility of these mixtures. With excess granular ice, however, the run-out decreased because ice particles bonded together to be larger ones and were difficult to involve inside the mass of granular avalanches. This indicates that the mixing of ice and rock particles played an important role to enhance the mobility of rock-ice avalanches. The smaller size ratio of ice particles and rock particles, the easier ice particles entered into the mass of the mixtures, the farther the mixtures moved. This work contributes to a better understanding of the role of granular ice in enhancing the mobility of rock-ice avalanches.