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Effects of coarse grain size distribution and fine particle content on pore fluid pressure and shear behavior in experimental debris flows

Kaitna, Roland and Palucis, Marisa C. and Yohannes, Bereket and Hill, Kimberly M. and Dietrich, William E. (2016) Effects of coarse grain size distribution and fine particle content on pore fluid pressure and shear behavior in experimental debris flows. Journal of Geophysical Research. Earth Surface, 121 (2). pp. 415-441. ISSN 2169-9003. doi:10.1002/2015JF003725.

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Debris flows are typically a saturated mixture of poorly sorted particles and interstitial fluid, whose density and flow properties depend strongly on the presence of suspended fine sediment. Recent research suggests that grain size distribution (GSD) influences excess pore pressures (i.e., pressure in excess of predicted hydrostatic pressure), which in turn plays a governing role in debris flow behaviors. We report a series of controlled laboratory experiments in a 4 m diameter vertically rotating drum where the coarse particle size distribution and the content of fine particles were varied independently. We measured basal pore fluid pressures, pore fluid pressure profiles (using novel sensor probes), velocity profiles, and longitudinal profiles of the flow height. Excess pore fluid pressure was significant for mixtures with high fines fraction. Such flows exhibited lower values for their bulk flow resistance (as measured by surface slope of the flow), had damped fluctuations of normalized fluid pressure and normal stress, and had velocity profiles where the shear was concentrated at the base of the flow. These effects were most pronounced in flows with a wide coarse GSD distribution. Sustained excess fluid pressure occurred during flow and after cessation of motion. Various mechanisms may cause dilation and contraction of the flows, and we propose that the sustained excess fluid pressures during flow and once the flow has stopped may arise from hindered particle settling and yield strength of the fluid, resulting in transfer of particle weight to the fluid. Thus, debris flow behavior may be strongly influenced by sustained excess fluid pressures controlled by particle settling rates.

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Palucis, Marisa C.0000-0003-0034-5810
Additional Information:© 2016 American Geophysical Union. Received 10 SEP 2015; Accepted 13 JAN 2016; Accepted article online 30 JAN 2016; Published online 25 FEB 2016. The authors would like to thank Michael Manga, Leslie Hsu, Leonard Sklar, Fritz Zott, Chris Ellis, Jim Mullin, and Stuart Foster for insightful discussions and help with sensor development and drum experiments. We particularly thank Anne Mangeney for insightful and critical review that significantly improved the manuscript. We also thank Michael Manga and Max Rudolph for training and use of the Haake Rheoscope1 for our rheology measurements. The discussion of the contraction and dilation cycles was inspired by an anonymous reviewer comment. This work was supported by the STC program of the National Science Foundation via the National Center for Earth-Surface Dynamics under the agreement EAR-0120914, the National Science Foundation grant CBET-0932735, and the Austrian Science Fund (J2837-N10). Marisa Palucis was partially supported by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA under the Mars Program Office. The experimental data may be obtained from R.K. (
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FWF Der WissenschaftsfondsJ2837-N10
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Record Number:CaltechAUTHORS:20160425-083159493
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Official Citation:Kaitna, R., M. C. Palucis, B. Yohannes, K. M. Hill, and W. E. Dietrich (2016), Effects of coarse grain size distribution and fine particle content on pore fluid pressure and shear behavior in experimental debris flows, J. Geophys. Res. Earth Surf., 121, 415–441, doi:10.1002/2015JF003725
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:66438
Deposited By: Tony Diaz
Deposited On:03 May 2016 03:22
Last Modified:10 Nov 2021 23:58

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