Granular collapse in a fluid: Role of the initial volume fraction

Abstract

The collapse of a granular column in a viscous liquid is experimentally investigated. The morphology of the deposits is shown to be mainly controlled by the initial volume fraction of the granular mass and not by the aspect ratio of the column, an observation which differs from dry granular collapse. Two different regimes are identified corresponding to initially loose and dense packings. Loose packings give rise to thin and long deposits, the dynamics being fast. A positive liquid pressure is measured below the column. For dense packings, the runout distance is twice less, the flow is slow, and a negative pore pressure is measured during the flow. These observations suggest that the dynamics of the granular collapse in a fluid is strongly affected by the dilatancy or contractancy behavior of the granular medium.

Commentary on "Granular discharge rate for submerged hoppers"

“…In particular, since the grains initially filling the hoppers are arranged in dense packing, the flow at the aperture, necessary involving shearing, may induce locally dilation and the sucking of water in the hopper, as it is the case in quick sands for instance. In [5], the pressure at the bottom of dense granular columns immersed in water at the onset of collapsing was found to be negative. Of course the systems are different, but the same mechanism may apply.…”

Mechanics of a granular skin

“…The column is anchored via capillary forces with the hydrophobic substrate at the bottom and is slightly flared close to the anchoring region. Under an identical protocol, hydrophilic beach sand instead slumps to form a canonical sandpile [31].…”

Modelling shallow debris flows of the Coulomb-mixture type over temporally varying topography

“…In the present study, we consider a saturated mixture, in which case the interstitial fluid may affect the value of the neutral angle. Rondon et al (2011) investigated granular collapses in a fluid and found there to be a roughly linear proportion between the initial solid volume fraction and the final deposition slope. In Coulomb-mixture theory, the solid normal stress at the base is assumed to be a fraction, 1 − f , of the total basal normal stress.…”