Richard M Iverson

DYNAMICS OF DEBRIS FLOWS AND ROCK AVALANCHES

Abstract: DYNAMICS OF DEBRIS FLOWS AND ROCK AVALANCHES Diverse geophysical mass flows involve rapid, gravity-driven motion of grain-fluid mixtures across three-dimensional terrain.  Dense geophysical mass flows (with grain volume fractions larger than about 0.4) dissipate energy primarily through direct grain-to-grain contacts mediated by intergranular fluid pressure.  Such flows include water-saturated debris flows and rock avalanches in which the interagranular fluid consists largely of air.  This specturm of flows can be modeled using a theoretical framework that is essentially a revision and generalization of the well-known Savage-Hutter model of granular avalanche motion resisted by Coulomb friction.  The model revisions described in this lecture include (1) use of rectangular Cartesian coordinate system rather than a fitted curvilinear coordinate system, (2) explicit estimation of vertical accelerations that modify the effect of gravity on internal stresses and basal tractions, (3) evaluation of Coulomb stresses using a finite-element calculation that enables stress components to be resolved into any coordinate system, including a rectangular Cartesian system.  Effects of pore-fluid pressure and physical experiments that motivate model formulation and test model predictions are also discussed.&

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