A TWO-PHASE DEBRIS-FLOW MODEL THAT INCLUDES COUPLED EVOLUTION OF VOLUME FRACTIONS, GRANULAR DILATANCY, AND PORE-FLUID PRESSURE — IJEGE
 
 
You are here: Focus and scope Issues from 2005 to 2017 5th International Conference on Debris-Flow Hazards "Mitigation, Mechanics, Prediction and Assessment" Topic 5 - Numerical Modelling of Debris Flows A TWO-PHASE DEBRIS-FLOW MODEL THAT INCLUDES COUPLED EVOLUTION OF VOLUME FRACTIONS, GRANULAR DILATANCY, AND PORE-FLUID PRESSURE
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A TWO-PHASE DEBRIS-FLOW MODEL THAT INCLUDES COUPLED EVOLUTION OF VOLUME FRACTIONS, GRANULAR DILATANCY, AND PORE-FLUID PRESSURE



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.

Authors:
David L. George - U.S. Geological Survey, 1300 SE Cardinal Ct., Vancouver - WA 98683 USA
Richard M. Iverson - U.S. Geological Survey, 1300 SE Cardinal Ct., Vancouver - WA 98683 USA
Keywords
Debris flow, dilatancy, pore pressure.
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