The more tired a dog is the less likely he is to get into any trouble. Booby trap him from the house. Try silently lobbing a shake can or two in his direction when he starts to dig. This is most effective if he does not see or hear you do this. Shake cans falling from the sky are a fine deterrent.
Prevention is the best cure.
If your dog is outside, supervise him. If you can't supervise him, don't leave him out. As with so many canine behavior problems, prevention is often the easiest route for both of you. You get the facts all of them here. Get concrete suggestions here.