"cohesionless material"

Ah - Trick Question!

The answer to 'critical angle' above is thus zero - all of it will spill over a practical surface, or spread infinitely out - sorta like one' dem 'SF Horror Movies'...


Another interesting thread of investigation...

"pile ... particles of uniform gradation upon a structure such as pile supported marine dock"

The 'Average weight' over the whole thing is just that - in the middle of the pile (assuming a 'critical angle' of greater than zero!) the greatest actual weight will be where the resultant slumped pile is highest - in the centre.

The 'average strength' of the dock doesn't matter - just where the greatest stress is - 'the weakest link in the chain' thingie...