Athermal Sediment Creep Triggered By Porous Flow

The dynamics of sediment creep under the stress of a porous flow, a situation ubiquitous in the environment, remains scarcely studied. To initiate such effort, experiments of a submerged quasi-two-dimensional sediment layer creeping downslope were performed, varying the setup tilt and a porous flow under the two respective thresholds for yielding. Logarithmic decay rates of the deformation are observed, with the rate increasing with both control parameters. A new dimensionless parameter, P*, accounting for the mean porous flow intensity and the distance to the yield stress, is proposed and allows a collapse of all the deformation results on a single curve. Two distinct creep regimes are identified and correspond to a weak but systematic change of the mean void size as P* increases.