A comparative assessment of rheological laws for mud flows

Climate change has increased the frequency of prolonged and intense rainfall events. As a result, increasingly frequent slurry flows, channelised landslides that occur on mountain slopes, have manifested all over the world causing extensive damage. On 15-16 December 1999 the municipality of Cervinara was hit by several slurry flows and some authors simulated the events considering the mixture as an equivalent continuous fluid. These models have adopted depth-averaged approaches, in which both internal and basal flow resistance are described by the bottom shear stress. By investigating the various rheological models applied, the comparisons highlighted the differences in terms of shear stress values with the same flow depth and unit discharge width. Despite these differences, the models applied satisfactorily to simulating the same event. A further rheological law is introduced, derived from the characterization in the laboratory of a mud reconstituted from a soil sample taken at the Cervinara site, which models the slurry as a shear-thinning fluid. Whatever the flow depth and flow conditions, the low shear-thinning index values imply an almost constant shear stress. Future simulations of the full event could reveal the performance of this bottom-up approach in predicting the consequences of a field-scale landslide.