The fluidization behaviour of ignimbrite at high temperature and with mechanical agitation

[1] Experiments were carried out to study the fluidization behaviour of ignimbrite at high temperature and while being mechanically agitated. Geldart group C behaviour occurs up to 565 C when the material is subjected to increasing gas flow (without agitation) from the loosely packed state. In contrast, even gentle mechanical agitation inhibits channelling and results in group-A type behaviour with homogeneous (non-bubbling) expansions of up to 30–40%. Bed collapse tests exhibit group-C behaviour at room temperature, group-A behaviour at 200–565 C, and transitional behaviour at 55 C. Both elevated temperature and mechanical agitation greatly increase the fluidizability of ignimbrite. It is inferred that a combination of high temperature and shear during transport will promote Geldart group A behaviour in pyroclastic flows.