In article ,
"Toy" writes:
| "Marcus Fox" wrote in
| message ...
|
| I am trying to calculate a formula to determine approximately how much
| earth/material I would need to create a "pile" - ...
|
| 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. ...

It's more general than that. The volume of anything that goes from
a point to a flat area by straight lines is 1/3 of the area multiplied
by the distance from the point to the plane of the flat area. The
same formula applies to cones, pyramids, ones that lean sideways, and
irregular shapes.

| 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.
|
| first it depends on the material.
|
| sand would have a shallower base angle for instance.
|
| if you have the same amount of material and it starts to spread out, without
| adding more material, the volume remains the same.
|
| or am I missing something here.

No, you are correct. To a first approximation, material poured onto
a pile will form a structure of the shape that the above formula
applies to - look at spoil heaps etc.

And the angle depends critically on the material and its dampness.
really dry sand may support only 15 degrees above the horizontal;
wet sand may reach 60. Earth is more cohesive than sand.


Regards,
Nick Maclaren.