Depletion-induced aggregation of rods enhanced by clustering is observed to produce a novel model of attractive pairs of rods separated by a line of spheres in a quasi-2D, vertically-shaken, granular gas of rods and spheres. We show that the stability of these peculiar granular aggregates increases as a function of shaking intensity. Velocity distributions of spheres inside and outside of a pair of rods trapping a line of spheres show a clear suppression of the momentum acquired by the trapped spheres. The condensed phase formed between the rods is caused by a clustering instability of the trapped spheres, enhanced by a vertical guidance produced by the confining rods. The liberated area corresponding to direct excluded-volume pairs and indirect depletion-aggregated pairs is measured as a function of time. The stability of rod pairs mediated by spheres reveals an attraction comparable in strength to the one purely induced by depletion forces.

Convection velocity measurements in vertically vibrated granular materials are presented. The convection velocity close to the walls grows quadratically with the difference between the maximum and critical, or excess, amplitude (proposed as a dynamic parameter to describe related problems) and it is shown numerically that the average bed-bottom relative velocity during the distancing between them, grows linearly with the squared as well. This is interpreted as the signature of an inertial shearing force or momentum transfer proportional to the bed-container relative velocity, acting mainly during the bed-plate distancing part of each cycle which leads to the formation of the convective flux.

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Binary mixtures of dry grains avalanching down a slope are experimentally studied in order to determine the interaction among coarse and fine grains and their effect on the deposit morphology. The distance travelled by the massive front of the avalanche over the horizontal plane of deposition area is measured as a function of mass content of fine particles in the mixture, grain-size ratio, and flume tilt. A sudden transition of the runout is detected at a critical content of fine particles, with a dependence on the grain-size ratio and flume tilt. This transition is explained as two simultaneous avalanches in different flowing regimes (a viscouslike one and an inertial one) competing against each other and provoking a full segregation and a split-off of the deposit into two well-defined, separated deposits. The formation of the distal deposit, in turn, depends on a critical amount of coarse particles. This allows the condensation of the pure coarse deposit around a small, initial seed cluster, which grows rapidly by braking and capturing subsequent colliding coarse particles. For different grain-size ratios and keeping a constant total mass, the change in the amount of fines needed for the transition to occur is found to be always less than 7%. For avalanches with a total mass of 4 kg we find that, most of the time, the runout of a binary avalanche is larger than the runout of monodisperse avalanches of corresponding constituent particles, due to lubrication on the coarse-dominated side or to drag by inertial particles on the fine-dominated side.