首页|Unraveling the effect of a two-layer system on the mobility of rapid gravitational flows
Unraveling the effect of a two-layer system on the mobility of rapid gravitational flows
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NSTL
Elsevier
Rapid gravitational flows such as debris avalanches and debris flows may entrain significant amounts of in situ material along their tracks, increasing their volume. Interactions between rapid gravitational flows and bed material are complicated. Especially, the physical mechanism of the fluidization has remained a mystery up to now. To gain a better understanding of the fluidization mechanism and influencing factors, we conducted flume experiments simulating the process of a flow overriding saturated bed material. Results showed that the overriding flow fluidized the bed material into a viscous state rather than liquefying saturated bed material. We also carried out a rheometer test on the saturated bed material. It revealed shear-thinning of the bed material. We deduced that shear thinning, and not liquefaction, was the principal mechanism for bed-material fluidization. Based on these results, a two-layer flow model was proposed using the classical depth-integrated approximation and the Saint Venant equation. It was assumed that both the dry rock avalanche and the impacted saturated bed material behaved as visco-plastic flows with different apparent viscosities. The model's two viscosity parameters were calibrated using the experimental run-out times and distances. We conclude from comparison of the tests and simulations, that our model well simulates the entrainment process.
NSTL
Elsevier
