Behaviours of pyroclastic and analogue materials, in dry and wet environments, for use in experimental modelling of pyroclastic density currents

Modelling pyroclastic density currents (PDCs) is a challenging yet essential element of hazard assessment. PDCs are unpredictable and internal processes are often difficult to measure directly. Analogue experiments have been an important tool for investigating internal PDC dynamics. Typically, analogue experiments have removed moisture from experimental materials to limit cohesion. However, this does not represent natural systems well, where moisture can be introduced into a PDC through a variety of processes. In this study, we characterise pyroclastic and analogue materials in dynamic (i.e. flowing), static (i.e. stationary), wet and dry experiments to explore fundamental frictional and fluidisation behaviours. The addition of moisture can lead to changes in material properties resulting in significant impacts on geomechanical behaviours (size, density, shear strength), fluidisation and flowability. This work highlights the importance of validating the material choice used in modelling experiments, especially in wet conditions.