WHILE DUMPING QUARRY ROCK AT STOCKPILE ON LOWER LEVEL MATERIAL HUNG UP IN ONE SIDE OF TRUCK BED CAUSING TRUCK BED TO LIST TO PASSENGER SIDE. DRIVER ATTEMPTED TO PUT BOX DOWN BUT RAM WAS IN A B IND & CONTINUED UP CREATING MORE LIST & CAUSING LOWER PIN ON RAM TO BREAK & OVERTURN BED. THE TRUCK CAB DID NOT TURN ONTO ITS SIDE ONLY THE TRUCK BED. EE BANGED HIS ELBOW ON THE PTO COLUMN CR