



 
Firstly, I would drop the assumption that the pile must be elliptical; a truck should be able to dump gravel fairly uniformly over a rectangle. Now, the angle of repose will depend on many things, but I think 30 degrees or better is a safe assumption. That means the height of the pile will be at least 1/4 its minimum width. A pyramid 16' x 16' x 4' contains about 12.5 yards of gravel, 16 x 16 x 4 x (1/3) x (1/27) so you should be OK, if the driver starts dumping in the middle of the drive and comes forward just a little as it's tipping. With damp crusherrun gravel I'm guessing you might get close to 45 degrees and it might actually need spreading to the side if the truck bed is low. Good luck!  


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