Experimental Study of Sand Transport

Experiments were made to determine the effects of sediment size, sediment concentration, and flow velocity on the depositional style of sand-sized particles in a highvelocity surgd. A dimdnsional analysis of the experimental system was performed in an effort to relate the experimental results to deposits from turbidity currents and overwash surges. A large part of each deposit was a result of deposition from suspension or mass emplacement. Fine and coarse sands are deposited primarily by mass emplacement, while medium sands result from deposition from suspension. These results suggested that grain size plays the dominant role in determining depositional style. Concentration has a lesser effect. For fine and medium sands, sediment volume concentrations of 20% and 40% were characterized by different styles of deposition. Several mechanisms currently described in the literature used to explain features produced by high-velocity surges may have to be revised or discarded in light of the experimental results. Moreover, the development of interfacial instabilities and deformed beds as a result of turbulent eddies impinging on a liquefied bed may have important implications with respect to soft-sediment deformation and unusual types of grading, though these areas require extensive study. Thesis Supervisor: Dr. John B. Southard Professor of Geology Title: