Runout distance of debris flows : experimental and numerical simulations

Pao Yue-kong Library Electronic Theses Database

Runout distance of debris flows : experimental and numerical simulations

 

Author: Chan, Chin-pang Leo
Title: Runout distance of debris flows : experimental and numerical simulations
Degree: M.Phil.
Year: 2001
Subject: Debris avalanches
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Civil and Structural Engineering
Pages: x, 122 leaves : ill. (some col.) ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1544784
URI: http://theses.lib.polyu.edu.hk/handle/200/4010
Abstract: The main objective of this paper is to study the runout distance of debris flow by experimental simulations and to compare the runout distance observed in experiments with numerical predictions. In the experimental study, we design a new flume for modelling the real scale debris flows, by ensuring the equivalence of three constitutive scaling parameters (Bagnold number, Savage number and friction number) and four geometric scaling factors (velocity factor, flow factor, yield stress factor and viscosity factor) between the model tests and real events. The first three parameters reflect the relative importance of dispersive force, the friction force and the viscous force at the microscopic level, while the latter four factors ensure that the same macroscopic governing equations are applicable to both model and prototype. Debris materials collected by the Geotechnical Engineering Office (GEO) of the Hong Kong Government from the site of the Tsing Shan Debris Flow of 1990 are used in our study. It is found that the seven scaling parameters and factors of experiments are comparable to those of the Tsing Shan Debris Flow. The development of debris fan and the maximum runout distance of debris flows are investigated as functions of various parameters (including slope gradient, deposition board gradient, granular content and cross section shape of flow channel). For experiments with a flat deposition board, a slope angle increase from 26o to 32o of the flume leads to 84% increase in the runout distance. However, a further 6oincrease (from 32o to 38o) in the flume slope only gives a 42% increase in the runout distance. In addition, the runout distance can increase by 59% on average when the flume cross-section is changed from rectangular to triangular for various debris materials with flume slope at 26o and deposition board slope at 0o. The experimental simulations results are then compared to the predictions of various theoretical models, including the dispersive model (Takahashi and Yoshida, 1979), constant friction slope model (Hungr et al., 1984), sled model (Heim, 1932) and DAN model (Hungr, 1995). The DAN model prediction (Hungr, 1995) is found to be more agreeable to our experimental results than the predictions by other models. In the DAN model simulations, the Voellmy constitutive model is found to yield agreeable results if proper values in friction and turbulence coefficients are employed.

Files in this item

Files Size Format
b15447844.pdf 6.433Mb PDF
Copyright Undertaking
As a bona fide Library user, I declare that:
  1. I will abide by the rules and legal ordinances governing copyright regarding the use of the Database.
  2. I will use the Database for the purpose of my research or private study only and not for circulation or further reproduction or any other purpose.
  3. I agree to indemnify and hold the University harmless from and against any loss, damage, cost, liability or expenses arising from copyright infringement or unauthorized usage.
By downloading any item(s) listed above, you acknowledge that you have read and understood the copyright undertaking as stated above, and agree to be bound by all of its terms.

     

Quick Search

Browse

More Information