EE WAS GOING TO WORK ON COWL TO REPAIR A BUSTED HOSE. HE WAS SITTING ON THE SIDE BOARDS. A COWORKER WENT TO ADVANCE A SHIELD TO ENSURE SOME OF THE LOOSE ROCK IN THE FACE WAS SUPPORTED. WHEN HE BEGAN TO ADVANCE THE SHIELD A PIECE OF ROCK 8' TO 10' LONG FELL STRIKING THE SHEAR DRUM IT BROKE AND A PIECE OF ROCK 2'X2'X8"" STRUCK EE.