โ Scribed by Pierre Evesque
No coin nor oath required. For personal study only.
It is demonstrated experimentally that 2-D embankments of granular material which are slightly confined and submitted to quasi-static cyclic bulldozing exhibit spontaneous grain convection and grain diffusion: on an average, the grains dive down along the bulldozer wall, rise up at 45 ยฐ from the vertical after having reached the bottom and end their loop by moving parallely to the lid towards the bulldozer. Grain motion exhibits randomness, so that grain mixing is achieved after a few cycles. Grain rotation occurs during convection; rotations are distributed inhomogeneously too.
Large spatial fluctuations and intermittency are observed during both diffusion and rotations. Mixing process is briefly studied; it exhibits complexity. Changes of boundary conditions, of sample size and shapes and effect of grain elasticity are investigated briefly.
We interpret these phenomena within the scheme of classical soil mechanics, using both a finite element technique and the yield design theory with simple boundary conditions. Specially dedicated experiments demonstrate, however, that use of such simple flat boundary conditions are able to explain neither the exact deformation process nor the real back and forth motions of grains.
An analogy with convection pattern in horizontally vibrated samples is made.
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