A two-phase debris-flow model that includes coupled evolution of volume fractions, granular dilatancy, and pore-fluid pressure

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Abstract

Pore-fluid pressure plays a crucial role in debris flows because it counteracts normal stresses at grain contacts and thereby reduces intergranular friction. Pore-pressure feedback accompanying debris deformation is particularly important during the onset of debrisflow motion, when it can dramatically influence the balance of forces governing downslope acceleration. We consider further effects of this feedback by formulating a new, depth-averaged mathematical model that simulates coupled evolution of granular dilatancy, solid and fluid volume fractions, pore-fluid pressure, and flow depth and velocity during all stages of debris-flow motion. To illustrate implications of the model, we use a finite-volume method to compute one-dimensional motion of a debris flow descending a rigid, uniformly inclined slope, and we compare model predictions with data obtained in large-scale experiments at the USGS debris-flow flume. Predictions for the first 1 s of motion show that increasing pore pressures (due to debris contraction) cause liquefaction that enhances flow acceleration. As acceleration continues, however, debris dilation causes dissipation of pore pressures, and this dissipation helps stabilize debris-flow motion. Our numerical predictions of this process match experimental data reasonably well, but predictions might be improved by accounting for the effects of grain-size segregation.

Additional publication details

Publication type Conference Paper
Publication Subtype Conference Paper
Title A two-phase debris-flow model that includes coupled evolution of volume fractions, granular dilatancy, and pore-fluid pressure
Year Published 2011
Language English
Publisher Università La Sapienza
Publisher location Padua, Italy
Contributing office(s) Volcano Science Center
Description 10 p.
Larger Work Type Conference Paper
Larger Work Title Debris-flow hazards : mitigation, mechanics, prediction, and assessment : proceedings of 5th international conference : Padua, Italy, 14-17 June 2011
Conference Title Debris-flow hazards : mitigation, mechanics, prediction, and assessment : proceedings of 5th international conference : Padua, Italy, 14-17 June 2011
Conference Location Padua, Italy
Conference Date June 14-17, 2011
Online Only (Y/N) N
Additional Online Files (Y/N) N