EMPLOYEE WAS LOCATED ON THE OFF SIDE OF THE #4 A BELT BETWEEN 17 & 18 BREAK. HE WAS IN THE PROCESS OF SHOVELING THE WALKWAY WHEN A COAL RIB MEASURING 12' X 5' X 2' FELL STRIKING HIM ON THE LOW ER LEFT LEG, PINCHING HIS LEG BETWEEN THE RIB AND THE BELT STRUCTURE.