There are 2 ways to solve this
1)Give the shovel to one of your main characters NOT to companions or henchemens,because if you trying to dig out a grave sometimes there is can be choise which you should make(to dig or not to dig but compainions cannot make choises)
2)If you currently controlling the main character then equip shovel and just click left mouse button on the mound
IIRC it should work
Last edited by James 540; 05/07/14 02:11 AM.