Hadn't thought of that, but you could probably create an effective barrier. However, I have no idea how deep you'd have to go, OR whether they will tunnel through rock dust.

You could check with a local exterminator.

Or, if I were going to try, I think I'd get something like the 6 x 12 patio blocks, and bury those 7" deep in a border around the pool - so the block was under 1" dirt. You'd need to be careful that the blocks touched each other tightly! Again, a local exterminator might have ideas about how best to do that.