The repose angle must depend strongly on the average shape of the sand grains, which would depend on the material (normally silica), the amount of wear, presence of moisture, etc. So the repose angle would be determined experimentally and is not a mathematical constant of any interest. But the angle would be independent of the pile size. Does anyone know differently? Steve Gray -----Original Message----- From: math-fun-bounces+stevebg=adelphia.net@mailman.xmission.com [mailto:math-fun-bounces+stevebg=adelphia.net@mailman.xmission.com] On Behalf Of Simon Plouffe Sent: Tuesday, April 03, 2007 7:55 AM To: math-fun Subject: [math-fun] pile of sand constant Hello, I have this information about a certain constant associated with a pile of sand. Apparently the ratio of the half the base to the height is approx. 4/3. I don't remember where I saw that for the first time, empirically, well at least for ordinary and dry sand, it looks like it is. In other words, a pile of sand will always have the same shape regardless of the size, or the slope is constant. Is there anybody that has any information about this phenomena? Is this known ? Simon Plouffe