2018/05/02 by Benjamin L. Allen, Allen, Benjamin, Arshad Kudrolli +1 · 1 citation
Earth and Planetary Sciences · Engineering · Environmental Science · #FOS: Physical sciences #Geological formations and processes #Granular flow and fluidized beds #Landslides and related hazards #Soft Condensed Matter (cond-mat.soft)
paper · pdf · doi:10.48550/arxiv.1805.00838
openalex publication_date 2018/05/02 · openalex created_date 2022/10/06 · openalex updated_date 2026/07/28
We show that a freshly sedimented granular bed settles and creeps forward\nover extended periods of time under an applied hydrodynamic shear stress, which\nis below the critical value for bedload transport. The rearrangements are found\nto last over a time scale which is millions of times the sedimentation time\nscale of a grain in the fluid. Compaction occurs uniformly throughout the bed,\nbut creep is observed to decay exponentially with depth, and decreases over\ntime. The granular volume fraction in the bed is found to increase\nlogarithmically, saturating at the random close packing value \φrcp\n\≈ 0.64, while the surface roughness is observed to remain essentially\nunchanged. We demonstrate that an increasingly higher shear stress is required\nto erode the bed after a sub-critical shear is applied which results in an\nincrease in its volume fraction. Thus, we find that bed armoring occurs due to\na deep shear-induced relaxation of the bed towards the volume fraction\nassociated with the glass transition.\n