EMPLOYEE USED DOZER TO PUSH A 60' LENGTH OF RAILROAD RAIL OUT OF THE WORK AREA. HE POSITIONED THE RAIL PERPENDICULAR TO THE DOZER BLADE. THE RAIL STOPPED MOVING FORWARD AND THE DOZER CONTINUED TO TRACK. THE RAIL BOWED AND SPRANG UP OVER THE DOZER BLADE AND CAME DOWN THROUGH THE LEFT SIDE CAB DOOR GLASS AND ONTO OPERATOR'S LEFT KNEE.