How do I get my dog to stop digging?

He's approx 8 years old (in human years), lab/chow mix and recently neutered (about 3 weeks ago). In the past 3-4 weeks he has dug more holes than he's ever dug; Im assuming there's a dog in heat somewhere in the neighborhood. He digs holes to get out of the yard. I've refilled the holes, put bricks, heavy flowerpots, a wrought iron table and chair...everything I could think of to line my fence so he can't dig an escape tunnel, yet he still gets out. He will literally move all of said items or dig around them so they fall over so he can squeeze by. Im at my whits end. Right now he's in my garage because I can't trust him in the yard anymore. I can't leave him alone while im at work because I know he'll get out. Luckily I have great neighbors who have called me to let me know they've found my dog. Im at my last resort. I love this dog like a child and would never get rid of him, but it's becoming impossible to keep him.