  Sandpiles have become paradigmatic systems for granular flow studies in
statistical physics. New directions of investigations are discussed here.
Rather than varying the nature of the pile (sand, salt, rice,..) we have
investigated changes in the boundary conditions. We have investigated
experimentally and numerically sandpile structures on bases having a fractal
perimeter. This type of perimeter induces the formation of a quite complex set
of ridges and valleys. A screening effect of the valleys is observed and
depends on the angle of repose. Binary granular systems have also been
investigated on such bases: a spectacular demixing is obtained along the
valleys. This type of phase segregation is discussed with respect to numerical
studies.
