Phalynx's attempt and a small underground shelter.

[glenn kangiser]

Sand and cement can make mortar - plaster - stucco etc.  For the backfill though the reason sand is often used under floors is that just water will pretty well compact it - damp and drive over it, it is compacted but can be moved easily.  Like at the beach.  the damp sand - not wet moves very little under the car tires.  No need for cement unless you just want to frustrate kitty.