Influence of Rock-Avalanche Fragmentation - Mobility Analysis focused on inter-fragment bonding strength

Alpine mass movements, such as rockslides and rock avalanches, pose significant natural hazards and drive landscape evolution in steep terrains. Understanding rock slope degradation, fragmentation, and the dynamics of failure and transport mechanisms is crucial for hazard prediction and mitigation strategies. This study examines the effects of rock fragmentation on the mobility and deposition behaviour of rock avalanches through experimental and theoretical approaches.

We investigate the role of internal bonding strength in influencing fragmentation dynamics and subsequent runout behaviour. A novel experimental setup simulates dynamic rock fragmentation in rock avalanches using a model block with varying internal bonding configurations. Therefore, graphite connectors of varying strength and number per block are used, combined with different layering techniques. These connectors undergo prior shear strength testing, allowing us to predict the force required to achieve specific fragmentation patterns. Additionally, they facilitate flexible variation not only in the material of the fragments but also in the way the connections between fragments are formed. Unlike previous research, this experiment stands out by employing connectors that link fragments at discrete points using pins rather than continuous surface bonding. This method enables the creation of complex geometric shapes for model blocks and facilitates the investigation of a wide range of block configurations in a controlled laboratory setting. This two-zone model allows for significant impulse changes and analysis before and after impact. By quantifying fragmentation patterns in the runout zone, such as angular distribution, lateral and longitudinal deposits, energy dissipation, and the force required for fragmentation, we highlight the influence of internal structures on avalanche mobility.

Our findings provide valuable insights into rock avalanches and address gaps in existing research regarding experimental block geometries and internal structures. The variation of input parameters in these small-scale experiments supports the validation and calibration of dynamic fragmentation models, which can be used for hazard zone mapping. This study emphasizes the importance of integrating experimental research with practical applications to improve hazard preparedness, risk reduction strategies, and community resilience in vulnerable areas.