That's terriers for you....it's what they're bred for! Digging! I have a really good toy...it's a ball you put biscuits in, and you make the hole in it small...they have to nudge it around and the biscuits fall out..keeps them interested for ages....or even a Kong with Peanut butter or something yummy in it.

The only other thing you can do is catch him in the act. There is no use once the damage is done. I don't think that rubbing their face in it does it (but that's just me) but a good firm NO does the trick. You don't want to make the dog afraid of you! If catching him in the act is difficult, then maybe cordon off the dog into a smaller area, then gradually make it bigger.

I'm lucky my pooch isn't a digger. He isn't allowed in the garden beds, but has free reign of the garden. I know it's difficult when kiddlies take up most of your time, but do try and spend time training your dog too....it will work wonders

Good luck