Journal of Mountain Science

, Volume 10, Issue 2, pp 233–238 | Cite as

Influence of fine sediment on the fluidity of debris flows

  • Norifumi Hotta
  • Takahiro Kaneko
  • Tomoyuki Iwata
  • Haruo Nishimoto


Debris flows include a great diversity of grain sizes with inherent features such as inverse grading, particle size segregation, and liquefaction of fine sediment. The liquefaction of fine sediment affects the fluidity of debris flows, although the behavior and influence of fine sediment in debris flows have not been examined sufficiently. This study used flume tests to detect the effect of fine sediment on the fluidity of laboratory debris flows consisting of particles with various diameters. From the experiments, the greatest sediment concentration and flow depth were observed in the debris flows mixed with fine sediment indicating increased flow resistance. The experimental friction coefficient was then compared with the theoretical friction coefficient derived by substituting the experimental values into the constitutive equations for debris flow. The theoretical friction coefficient was obtained from two models with different fine-sediment treatments: assuming that all of the fine sediments were solid particles or that the particles consisted of a fluid phase involving pore water liquefaction. From the comparison of the friction coefficients, a fully liquefaction state was detected for the fine particle mixture. When the mixing ratio and particle size of the fine sediment were different, some other cases were considered to be in a partially liquefied transition state. These results imply that the liquefaction of fine sediment in debris flows was induced not only by the geometric conditions such as particle sizes, but also by the flow conditions.


Debris flow Fine sediment Friction coefficient Liquefaction Open channel Reynolds stress 


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Copyright information

© Science Press, Institute of Mountain Hazards and Environment, CAS and Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  • Norifumi Hotta
    • 1
  • Takahiro Kaneko
    • 2
  • Tomoyuki Iwata
    • 3
  • Haruo Nishimoto
    • 1
  1. 1.Faculty of Life and Environmental SciencesUniversity of TsukubaIbarakiJapan
  2. 2.Faculty of AgricultureThe University of TokyoTokyoJapan
  3. 3.Graduate School of Agricultural and Life SciencesThe University of TokyoTokyoJapan

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