A method for estimating the bed-sediment entrainment in debris flow

Zheng Han, Guangqi Chen

Research output: Contribution to conferencePaperpeer-review

Abstract

The immense destructive impact induced by debris flow in mountainous region endangers human lives and infrastructure facilities. Previous studies have long indicated that the fatalities in a debris-flow event depend on the volume of debris flow, which may be conspicuously amplified by entraining bed-sediment along the trajectory as it descends the slope. Several lines of evidence by the previous studies have also highlighted this viewpoint that debris flow can grow dramatically in magnitude as accompanying by the entrainment. In this paper, we present an elementary model to estimate the dynamic entrainment rate of bed-sediment when overridden by debris flow. Following the preliminary studies done by Iverson (2012) and Medina et al. (2008), a temporal entrainment rate can be computed basing on the momentum conservation of the two-layer system. To take into account the influence of the pore water pressure on the entrainment rate, we employ two parameters, λ1 and λ2 into the model, which denote the saturate degree of debris flow and bed-sediment, respectively. Our approach demonstrates that if flow layer and bed layer shares the same friction angle, the condition λ21 should be satisfied to provoke the entrainment. The performance of the approach is firstly tested on a simple scenario with the parameters of typical value, and then a debris-flow event that occurred in 2010 at the Yohutagawa torrent, Japan. The computed entrainment rate and accumulated depth show a good agreement with the in-situ surveys. Another advantage of our approach rests on the fact that entrainment rate is written in a differential form, thus it can be easily incorporated to the mass constitutive equation of the numerical model using a shallow water approximation.

Original languageEnglish
Pages1089-1093
Number of pages5
DOIs
Publication statusPublished - Jan 1 2015
Event15th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2015 - Fukuoka, Kyushu, Japan
Duration: Nov 9 2015Nov 13 2015

Other

Other15th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2015
CountryJapan
CityFukuoka, Kyushu
Period11/9/1511/13/15

All Science Journal Classification (ASJC) codes

  • Geotechnical Engineering and Engineering Geology
  • Soil Science

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