Other trapped graves in the game usually explode as an invisible mine at the center of the grave. You can usually avoid death by digging with a character who has high CON and fire resistance while the rest of the party keeps their distance - that's how I dug up every grave around Cyseal's old church without having to reload.
Yup, thats the way to do it
No 'save cheating' or immersion breaking this way, just being cautious and using the game mechanics as they were intended (I guess).
