Detachment of dilatant soil due to high hydraulic shear stresses explained
M. van Damme (TU Delft - Hydraulic Structures and Flood Risk)
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Abstract
When soil surfaces are exposed to high shear stresses induced by high-velocity water flows, they erode. Erosion consists of the detachment, entrainment and transport of soil particles. When exposed to high shear stresses the process of soil detachment is no longer given by the pick-up of individual particles but by the continuous shear failure of layers of soil. The understanding of how soil properties influence the detachment rate of soil is lacking. This paper presents how the bed shear stress, initial and critical porosity, hydraulic conductivity, and density influence the detachment rate of dilatant soils which are subjected to high-velocity flows. Based on the constitutive mass and momentum balance equations it is hypothesized that the exchange of mass and momentum during soil detachment corresponds with that situation for which the dilatancy induced shear resistance of the soil is maximum. The hypothesis is validated against high-velocity erosion experiments on sand.
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