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Open AccessFeature PaperArticle

Experimental Analysis of Velocity Distribution in a Coarse-Grained Debris Flow: A Modified Bagnold’s Equation

1
Department of Engineering, University of Palermo, 90128 Palermo, Italy
2
Faculty of Engineering, University Enna Kore, 94100 Enna, Italy
*
Author to whom correspondence should be addressed.
Water 2020, 12(5), 1415; https://doi.org/10.3390/w12051415
Received: 26 February 2020 / Revised: 8 May 2020 / Accepted: 11 May 2020 / Published: 15 May 2020
Today, Bagnold’s theory is still applied to gravity-driven flows under the assumption of uniform sediment concentration. This study presents findings of flume experiments conducted to investigate the velocity and concentration distributions within the debris body by using high-resolution images. The analysis has shown that the concentration and mobility of grains vary along the depth. A linear law to interpret the grains concentration distribution, starting from the knowledge of the packing concentration and of the surface concentration, Cs, has been identified. By considering such a law, modified expressions of the Bagnold’s number and the velocity in stony-type debris flows are also presented. By using these expressions, three regimes of motion have been identified along the depth, and the velocity profile within the debris body is determined as a function of the parameter Cs. It has been verified that the velocity profiles estimated by using the modified equation compare well (mean square error less than 0.1) with the literature’s measured profiles when Cs is correctly measured or estimated. Results of cutting tests, conducted for a sample of the used material, have also allowed us to verify that Cs could be determined as a function of the static friction angle of the material. View Full-Text
Keywords: debris flows; flow velocity; sediment concentration; prevision debris flows; flow velocity; sediment concentration; prevision
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Termini, D.; Fichera, A. Experimental Analysis of Velocity Distribution in a Coarse-Grained Debris Flow: A Modified Bagnold’s Equation. Water 2020, 12, 1415.

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