Influence of fine sediment on the fluidity of debris flows
- 169 Downloads
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.
KeywordsDebris flow Fine sediment Friction coefficient Liquefaction Open channel Reynolds stress
Unable to display preview. Download preview PDF.
- Egashira S, Ashida K, Yajima H, Takahama J (1989) Constitutive equations of debris flow. Annals of the Disaster Prevention Research Institute, Kyoto University 32(B-2): 487–501. (In Japanese with English summary)Google Scholar
- Egashira S, Miyamoto K, Itoh T (1997) Constitutive equations of debris flow and their applicability. In: Proceedings of the 1st International Conference on Debris-Flow Hazards Mitigation, San Francisco, California, US, 7–9 August 1997. pp 340–349.Google Scholar
- Hotta N, Miyamoto K (2008) Phase classification of laboratory debris flows over a rigid bed based on the relative flow depth and friction coefficients. International Journal of Erosion Control Engineering 1(2): 54–61.Google Scholar
- Itoh T, Egashira S (1999) Comparative study of constitutive equations for debris flows. Journal of Hydroscience and Hydraulic Engineering 17(1): 59–71.Google Scholar
- Nishiguchi Y, Uchida T, Tamura K, Satofuka Y (2011) Prediction of run-out process for a debris flow triggered by a deep rapid landslide. In: Genevois R, et al. (eds.), Debris-Flow Hazards Mitigation: Mechanics, Prediction and Assessment. Casa Editrice Universita La Sapienza, Roma. pp 477–485.Google Scholar
- Takahashi T (1977) A mechanism of occurrence of mud-debris flows and their characteristics in motion. Annals of the Disaster Prevention Research Institute, Kyoto University 20(B-2): 405–435. (In Japanese with English summary)Google Scholar
- Takahashi T, Kobayashi K (1993) Mechanics of the viscous type debris flow. Annals of the Disaster Prevention Research Institute, Kyoto University 36(B-2): 433–449. (In Japanese with English summary)Google Scholar