EE WAS REMOVING OUTSIDE DUAL ON LUBRICATION TRUCK. TIRE SIZE UR 24.5-14 PLY-100 PSI NON SPLIT RIM A ROCK HAD WEDGED BETWEEN DUALS. AS LAST LUG ONUT WAS REMOVED FROM OUTSIDE DUAL THE INSIDE DUA L BLEW OUT. ROCK WAS THROWN OUT AND STRUCK FENDER WELL. SHEET METAL BULGED OUT AND STRUCK EE ON HARD HAT AND GLASSES.