Importance of liquid bridge forces in dynamics of rock-ice avalanches: insights from discrete element simulations

Abstract

Rock-ice avalanches imminently threaten high-mountain and glacierized regions. The wet rock-ice particle flow exhibits dependence on pendular liquid bridges; however, its mechanisms are unclear. This paper focuses on the influence of interstitial water in the pendular regime on the dynamics of rock-ice avalanches. A scheme was proposed to incorporate capillary and viscous liquid bridge forces into the discrete element method (DEM) for simulating the wet rock-ice particle flow. Numerical results indicate that the proposed scheme could well reproduce the key experimental outcomes of small flume tests. The liquid bridges could reduce the mixture mobility remarkably via pseudo-cohesion, which was mainly attributed to the capillary force. The pseudo-cohesion effect could alter the collision-dominant flow regime to the shear-dominant regime through buffering collisions and suppress the segregation through impeding the downward penetration of gravels. A very small amount of water, too little to form liquid bridges, could lubricate the sliding surface, and increase the mixture mobility. The role of the critical inter-element separation distance was deterministic in DEM for wet particles. This paper demonstrated the crucial impact of the liquid bridges in the dynamics of rock-ice avalanches and offered a promising scheme for deeply understanding the solid–liquid interactions in wet rock-ice avalanches.