DURING A WEEKLY AIRCOURSE EXAM A FALL WAS FOUND 20' OUTBY STATION #1860 IN #2 ENTRY OF NORTH MAINS. THE FALL IS ABOUT 40' LONG, 18'-20' WIDE AND 6'-7' HIGH. THE AREA WAS BOLTED WITH 60"" INSTAL L ROOF BOLTS WITH 6"" X 16"" PLATES & SKINS. CABLE BOLTS WERE OBSERVED IN THE SURROUNDING AREAS. VENTILATION WAS NOT INTERRUPTED. NO MEN OR EQUIPMENT WERE INVOLVED.