INJURED WAS HELPING CHANGE OUT A TRAM MOTOR ON A MINER. HE WAS SITTING IN THE SCOOP BUCKET WHICH THEY USED TO CHANGE THE MOTOR WITH WHEN A PIECE OF DRAW ROCK FELL OUT BETWEEN BOLTS, MEASURING 17' LONG, 3' WIDE & 1/4"" THICK ON ONE END & 7"" ON THE OTHER END. THE ROCK STRUCK HIS SHOULDER & PUSHED HIM OVER HURTING HIS BACK.