[jashan]

you must not be letting your dog for walk or exercise
thats why he use his energy digging so that he can do little bit of exercise
or your dog must be chained all the day and when he is free he is very happy
and just start digging
or the area where he diggg may be smeelling something or something must be dug inside the are where your dog digs
ur friend
jashan(jatt)