LABORATORY AND NUMERICAL STUDY OF MUD AND DEBRIS FLOW. (VOLUMES I AND II)

The presence of high concentrations of suspended sediment affects the physical and dynamic properties of mud and debris flows. At a critical concentration of suspended sediment, which depends on the fraction of fine particles, the water-sediment mixture has rheological properties that are very different from those of clear water. Turbulence intensities, velocity gradients, flow resistance and sediment transport capacities for mud and debris flows are different from those for clear water flow.;The rheological measurements showed that the bentonite mud is a non-Newtonian fluid that possesses properties of an elastic solid. The yield stress and viscosity decrease with an increase in the shear rate.;A one-dimensional numerical model accurately simulated unsteady mud flows generated in the laboratory flume over a wide range of concentrations of solid particles when the flow resistance was defined by constitutive relations based on the rheological measurements.;A series of unsteady, non-uniform mud flows was generated in a laboratory flume to enhance the understanding of dynamics of mud and debris flows. The fluid mud was represented by bentonite slurries of varied concentrations of solid particles. Samples of mud from most of the flume test were analyzed to identify the characteristics and rheological properties of the fluid mud.