EE WAS INSTALLING 1 ST BOLT IN #5 CROSSCUT WHEN A PIECE OF ROCK FELL IN FRONT OF ATRS AND END OF ROCK STRUCK EE ON THIGH. EE WAS TREATED AT A MEDICAL FUCILITY AND RELEASED TO RETURN TO WORK AT REGULAR DUTY. THIS EE WORKS A FOUR ON FOUR OFF WORK SCHEDULE AND WAS A LOT DUE TO WORK UNTIL 10-01-01 AND HE FAILED TO REPORT TO WORK DUE TO PAIN IN AREA OF INJURY./