EE WAS DRIVING A 30T MOXY TRUCK ON THE EXIT HILL OF THE #28 QUARRY. THE HILL HAD ROCK ON IT AND EE ATTEMPTED TO STRADDLE SOME ROCKS THAT HAD BEEN LOST ON THE PREVIOUS LOAD. THE FRONT FRAME OF TRUCK CAUGHT THE LOOSE ROCK AND THREW IT UNDER FRONT TIRE CAUSING CAB & BED TO TWIST. EE EXPERIENCED BACK/HIP PAIN & TAKEN TO CO. DR. THEN WENT TO OWN DR & TOLD TO BE OFF WORK 2 WEEKS & THERAP