Preventing Rodents (rats) from Returning to existing burrows
Rats leave behind a scent as they enter and exit burrows. When you "evicted" those rats, that scent was still there and at some point, another rat came across it and thought "Hey, someone else was digging here, there must be something good there!" and started digging again. That's how you always end up with rats re-digging tunnels or chewing through a blockage in a hole, they appear to be pre-programmed to investigate anything that another rat has done and given that they tend to be prey for so many types of predators, its a good survival strategy for the species.

The thing that I found has worked is to get fox / coyote urine crystals and sprinkle them around the area after you evict them. That overrides their curiosity factor with a danger factor. You can order it on-line from numerous sources. Just be forewarned; your dogs will be VERY VERY interested in that smell too. This by the way also works to keep skunks away from going under porches and decks.

I am currently experimenting with pouring liquid ammonia around their excavations to see if that has a similar effect, based on the fact that urine eventually breaks down into that at some point. So far so good actually, but right now is the peak of their invasion season as they begin looking for places to raise their babies, so it remains to be seen if it really stops the onslaught.