Uniaxial compressive strength and crack propagation of debris-ice mixtures: Insights from experiments and particle-based modeling

Abstract

The compressive strength and crack propagation behavior of debris-ice mixtures are crucial for assessing cold-region geohazards, particularly for interpreting the initiation mechanisms of rock-ice avalanches. This study reveals the failure characteristics under uniaxial compression through experiments and discrete element modeling (PFC^3D), providing key parameters for the initiation dynamics model of rock-ice avalanches through strength degradation and crack network evolution. The numerical simulation results strongly agree with the experimental results, with a maximum deviation of 6.32 % in the compressive strength and elastic modulus. The findings reveal that rock debris significantly redirect crack propagation by inducing bypass trajectories or crack arrest, rather than allowing direct fracture paths. The compressive strength increases with enlarging rock debris volume fraction but decreases with rising temperature and debris size. The loading rate governs failure mode transitions from plastic deformation (shear-slip dominated) to brittle fracture (tensile-penetration dominated), with peak strength occurring at a critical rate of 1 mm/min in the ductile-to-brittle transition regime. Furthermore, reduced debris porosity enhances the interfacial cementation strength, improving the integrity of debris-ice composite. Crack evolution progresses through three distinct phases: initial nucleation, slow nonlinear propagation, and rapid linear expansion, with tensile cracks dominating 56.9 % of the total fractures. The results provide new insights into the failure mechanisms of multiphase geological materials, offering practical guidance for engineering geology applications, particularly in understanding the initiation and evolution of rock-ice avalanches in periglacial environments, as well as for slope stability prediction and hazard mitigation in cold regions.