On Mon, 13 Sep 2004 02:23:52 GMT, Marcus Fox wrote:

I am trying to calculate a formula to determine approximately how much
earth/material I would need to create a "pile" - for want of a better word -
of a given height I could use just earth, but I could also have a pile of
rocks covered by earth.

The pile will be approximately cone shaped, and I know the formula to
calculate the volume of a cone. 1/3 pi r2 (base radius) x height. However,
since the soil will spread out and the base gets wider as the height
increases, I need to know to what degree this will happen, for example what
is the smallest slope in degrees where the pile will remain stable? 45? If
this is the case then the radius of the base will be the same as the height.

Your problem is not one of geometry. It is one of geology: what
is the angle of repose of a certain soil?

Easily solved. Just start shovelling the soil into a narrow pile.
It will, if you shovel accurately, form a conical heap that you
can measure. This will give you the *steepest* angle you can
maintain.

A reminder that wet soil behaves differently dry soil and a
stable heap of dry soil can be expected to sag when soaked by
rain. Coarse gravel, though it too has a characteristic angle of
repose, would not sag much, if at all.


--
Rodger Whitlock
Victoria, British Columbia, Canada
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