Longitudinal Surface Profiles of Granular Debris Flows

by Chyan-Deng Jan, U.C. Berkeley, Berkeley, United States,
Hsieh Wen Shen, U.C. Berkeley, Berkeley, United States,

Document Type: Proceeding Paper

Part of: Hydraulics/Hydrology of Arid Lands (H²AL)


Longitudinal surface profiles of granular material flowing down an inclined plane were studied by means of theoretical analysis and laboratory experiments. There are two driving forces acting on the granular material. One is a gravity force component along the inclined plane and the second is a force induced by lateral pressure gradient. The lateral earth pressure theory used in soil mechanics was expanded for granular debris flow. The total resistant stress acting on granular flows was treated as the linear sum of a rate-independent, contact friction part and a rate-dependent, viscous part. The former was expressed as a Mohr-Coulomb relationship. The latter was expressed as a friction slope relating to flow velocity and flow depth. According to this forgoing assumptions and the balance of longitudinal momentum, a method to calculate the longitudinal surface profiles was developed, by using a moving coordinate. Experiments with 5 mm glass beads were conducted in a conveyor-belt flume. Preliminary results suggest that the slope of the surface profile of granular flow decreases as the flume slope increases, and the slope of the surface profile increases as the belt speed increases. Experimental results were also compared with theoretical results.

Subject Headings: Slopes | Gravity forces | Lateral pressure | Overland flow | Granular materials | Debris | Solids flow | Flow profiles

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