On the transport mechanism of rockfalls and avalanches
Lacy, Jeffrey Michael
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In this thesis, a numerical model of a granular shear flow is developed. This model is two-dimensional and assumes the shearing granules to be identical, smooth, semi-elastic circular disks. The field containing these disks is bounded on the top and bottom by solid blocks of disks with the same properties. The field is bounded on the right and left by periodic boundaries. The top boundary block has an assigned horizontal velocity and overburden mass, and is unconstrained in the vertical direction. The base boundary block is immobile and does not permit scour. The numerical model is then used to test the hypothesis that, for large overburden pressures, collisions in the shearing region occur involving more than two particles, and that these multi-particle collisions act to reduce the shear strength of the dilatant granular flow. Flows were modeled for a variety of shear speeds and overburden pressures. Results of these simulations show that, although multi-particle collisions do occur with increasing frequency as overburden is increased, they do not have any significant effect on the shear strength of the granular flow. Therefore, this hypothesis is rendered invalid.