I would NOT bury any caches at all. However, I have found a cache that was in a very large coffee can that was buried. The lid was covered with just maybe a sprinkling of sand. After pulling the lid off, the cache was inside - in another container. So technically, the cache was not buried, but it was in another container that was buried, but not under any real amount of sand. (no digging required)It was hard to find, but it was a great hide. Thats the closest to burying that I would imagine doing. I would also leave some sort of hint/marker on the scene. Some of the older caches 2000/2001 were buried in public historical places and the geocachers digging little holes everywhere to find them gave geocaching a bad name. So be very carefull and avoid it if you can.