Substantiation of debris flow velocity from super-elevation: a numerical approach

Md Aftabur Rahman, Kazuo Konagai

Abstract

The use of super-elevations that a forced vortex flow leaves on the valley walls of a curved flume is a plausible approach toward estimating debris flow velocities in earthquake-induced geo-hazard studies. The centrifugal force of a speeding flow is responsible for a higher flow depth on the outer bend. However, in reality, a flow is not steady, and only the highest flow-marks are left at the outer and inner bends of the flow, which can lead to an inaccurate estimation of the actual velocity. Seeing the real scenario of the field, a series of numerical flume tests using smoothed particle hydrodynamics (SPH) is conducted to validate the estimation of debris flow velocities from flow-marks. Velocities estimated from flow-marks are lower than real velocities near the source region, but they converge to real velocities as the distance to the source increases. Based on several simulations, a best-fit line is proposed for adjusting debris flow velocity from mud-marks, and it is used to estimate flow velocities of the well-documented debris event called “Shiraito river debris flow,” which happened near the rim of the Hakone Crater, Kanagawa Prefecture, Japan, ensuing from the 1923 Great Kanto earthquake.

Original languageEnglish
Pages (from-to)1-15
Number of pages15
JournalLandslides
DOIs
StateAccepted/In press - 2016 Jun 27

Fingerprint

Debris
Flow velocity
Earthquakes
Hazards
Vortex flow
Hydrodynamics
Rivers

Keywords

  • Mud-marks
  • Smoothed particle hydrodynamics (SPH)
  • Super-elevation
  • Velocity

ASJC Scopus subject areas

  • Geotechnical Engineering and Engineering Geology

Cite this

Substantiation of debris flow velocity from super-elevation : a numerical approach. / Rahman, Md Aftabur; Konagai, Kazuo.

In: Landslides, 27.06.2016, p. 1-15.

Research output: Contribution to journalArticle

Rahman, Md Aftabur; Konagai, Kazuo / Substantiation of debris flow velocity from super-elevation : a numerical approach.

In: Landslides, 27.06.2016, p. 1-15.

Research output: Contribution to journalArticle

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AB - The use of super-elevations that a forced vortex flow leaves on the valley walls of a curved flume is a plausible approach toward estimating debris flow velocities in earthquake-induced geo-hazard studies. The centrifugal force of a speeding flow is responsible for a higher flow depth on the outer bend. However, in reality, a flow is not steady, and only the highest flow-marks are left at the outer and inner bends of the flow, which can lead to an inaccurate estimation of the actual velocity. Seeing the real scenario of the field, a series of numerical flume tests using smoothed particle hydrodynamics (SPH) is conducted to validate the estimation of debris flow velocities from flow-marks. Velocities estimated from flow-marks are lower than real velocities near the source region, but they converge to real velocities as the distance to the source increases. Based on several simulations, a best-fit line is proposed for adjusting debris flow velocity from mud-marks, and it is used to estimate flow velocities of the well-documented debris event called “Shiraito river debris flow,” which happened near the rim of the Hakone Crater, Kanagawa Prefecture, Japan, ensuing from the 1923 Great Kanto earthquake.

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