LABORATORY EXPERIMENTS OF PULSED SUBAQEOUS SEDIMENT DENSITY FLOWS: INTERNAL STRATIFICATION AND LAYERING

This paper reports on an experimental study which focuses on reproducing small scale sediment density flows in a laboratory flume. The observations are aimed at improving the parametrization of the relations that govern the transition between different phases of the flows. Dense mixtures of plastic sediment of variable grain size (thermoplastic polyurethane) and water were fed into the water-filled flume by gravity from a supply tank. Different grain-size and slope combinations were examined and the resulting velocity fields were obtained using UVP (Ultrasonic Velocity Profile) at various points along the channel. The flow was imaged through the transparent sidewall to track the velocity of the flow head for each test case. Image analysis also allowed a qualitative characterization of the vertical density stratification and water entrainment during runout. The runout distance and flow thickness are used to highlight the differences in the dynamic behavior of the flow for each test case. Data gathered from the experiments will be exploited in the further development of predictive numerical models for slide-induced debris flows transitioning to turbidity currents.