EMPLOYEE RECEIVED CONTUSIONS AND LACERATIONS TO THE HEAD WHEN THE GRADER DOOR SLAMMED SHUT ON HIS HEAD. THE GRADER WAS BEING USED TO LEVEL THE GROUND AT THE STOCKPILE AREA. THE GROUND WAS VERY HARD THE BLADE WAS CATCHING AND BINDING. AT ONE TIME IT CAUGHT HARD AND EMPLOYEE STUCK HIS HEAD OUT THE RIGHT SIDE OF THE CAB DOOR TO SEE WHAT IT WAS CATCHING. BLADE BROKE FREE THEN CAUGHT.