Living in a very heavily populated snake area (mainly Black's, Brown's, and Copperheads)as we do, you can do all you like to keep them at bay. But the simple fact is this ..... they will still be there!!! I have seen snakes dig into a yard (a Red Belly), I have seen them climb up chain mesh and they keep persisting. Black's and Copperheads will generally stay away from dogs, but Brown's and tigers won't.
What we have found is mow the area outside the pens (4-5m) and don't build pens in the bush. Also, don't have piles of rubbish or wood etc around the area. The more open, the better. It does seem to help, but we still end up killing a couple every year.
Also, something to remember. The red belly is a natural predator to the brown. It's much better to have those guys around than browns!!!!