our dogs were really bad at digging for a little while. when we would catch them doing it, we would just tell them "no" and then pick them up and bring them in, and wash their paws off, then put them into their cage for a little while for time out.
they hate having their paws washed.
i think that in conjunction with the time out somehow sunk in for them as not being worth digging the holes anymore.
good luck!