Investigation on collapse dynamics of ice-sand bi-frictional mixtures using material point method

Climate warming is associated with increased activity and significantly larger magnitudes of ice-rock avalanches in high-altitude mountainous regions. The contrasting physical properties of ice and rock contribute to the distinctive dynamics of ice-rock avalanches. In this study, the dynamics and packing characteristics of ice-rock avalanches were explored through numerical column collapse of ice-sand bi-frictional mixtures using the material point method with a concentration-dependent rheology model. The findings revealed that ice content and resistance-reducing effect of ice grains significantly affect the run-out distance. An effective initial aspect ratio (defined as the ratio of the initial height to the initial radius of the column) is scaled exponentially with ice content to derive a unified scaling relationship. Such a coefficient can be used to predict the flow regime, taking into account the influence of ice contents. This study concludes that ice-sand mixtures primarily exhibit inertial and liquid-like flow regimes as a result of low-friction interactions, thereby contributing to enhanced mobility. Finite-size analysis shows similarities with natural geophysical mass flows and can be extended to the prevention and mitigation of ice-rock avalanches.