On the supraglacial rock avalanches: Thermo-hydro-mechanical analysis considering ice-water phase transition

Abstract

The hypermobility of a large landslide makes it usually a catastrophic event whose mechanism is, however, not yet completely understood. As for supraglacial rock avalanches which typically occur in glacial environments, the runout can reach several to more than a dozen kilometers with a maximum velocity over 100 ms−1 and the mobility can be even stronger than that of the normal rock avalanches travelling on a rocky terrain. This phenomenon suggests a strong resistance reduction mechanism, such as ice melting, entrainment of ice and snow, and mass and momentum transfers between the solid and liquid components. Here we generalize the thermo-hydro-mechanical (THM) coupling analysis to study supraglacial rock avalanches taking into account ice-water phase transition due to frictional heating. Based on the fact that supraglacial avalanches can travel a long distance on the glacier surfaces whose path material mainly contains ice and snow, the ice content in the slip band can be relatively high which contributes to the basal lubrication as the ice melts. To assess the validity of the model, the 2016 Lamplugh supraglacial rock avalanche is chosen as a case study and the results are validated by comparisons with that from the seismic wave inversion, which suggests the THM analysis can capture the main characteristics of the supraglacial rock avalanche. A set of sensitivity analyses demonstrate the significance of considering the heat production and the ice-water phase transition, and principle factors are subsequently discussed. In particular, it is found that unlike normal rock avalanches in positive temperature environments, the initial temperature and porosity are significant for the initiation and motion processes of supraglacial rock avalanches in glacial environments.