EMPLOYEE CLAIMS THAT AFTER HE BACKED HIS HAUL UNIT TO THE CRUSHER DUMP HOPPER AND RAISED THE BED OF THE HAUL UNIT, A LARGE BOULDER IN THE BED OF THE TRUCK GOT HUNG-UP AND WOULD NOT ALLOW THE M ATERIAL TO FLOW OUT OF THE BED OF THE TRUCK. THE WEIGHT OF THE MATERIAL CAUSED THE FRONT END OF THE HAUL UNIT TO COME OFF THE GROUND. THE FRONT END CAME DOWN HARD CAUSING DRIVER SHARP BACK PA