EMPLOYEE STATED HE HURT HIS BACK WHILE PUSHING A LARGE ROCK OUT OF THE WAY (A SHORT AREA) THE BLADE OF THE #103 D11R DOZER SLIPPED OFF THE SIDE OF THE ROCK HE WAS PUSHING. THIS THREW HIM SIDEW AYS IN THE SEAT, CAUSING PAIN AND TWISTING HIS BACK. HE WAS WEARING A SEAT BELT. EE STARTED MISSING WORK ON 5-21-02, PAIN IN BACK.