PERMFILE111363 - Laserfiche WebLink

Home Browse Search

Areas in which the overburden over the extracted seam approaches zero are critical to longwall systems. The country rock in these areas are usually weathered and fractured because of its proximity to the outcrop. The roof rack can break up right up to the surface, placing the total weight on the longwall roof supports and gate entries. There are no calculable values for the minimum overburden over longwalls as this depends on a wide range of factors such as compaction and strength of the roof rock, tectonic stresses and configuration of the surface. BME has selected 150 feet as the minimum overburden thickness to ensure a dependable, controllable longwall system. III.A.2.c Mining Method Decision. The above criteria governed the selection of the mining system as shown on Map 119. The areas close to the outcrop on the south of the mining area were unsuitable for longwall mining due to the low overburden height. Room and Pillar panels RP-1 and RP-2 in the D Seam were excluded from longwall mining because the boundary geometry did not allow longwall mining. Previously designed longwall panels to the west of the West Mains in the D Seam were eliminated in the new mine plan because the coal seam is thin and consists of partings, and it overlies better coal in the B Seam. In BME's opinion the B Seam coal under this portion of the D Seam should not be jeopardized. BME has designed a mining plan which will give the highest resource recovery in the safest and most economical manner. III.A.3 Mining Sequence Maps 119 and 120 show the mine plan and development sequence for the D Seam and the B Seam, respectively. Initial mining began with the D Seam portals. Underground access to the coal seam has been provided by two declined rock tunnels: one double-compartment decline and one single-compartment decline. The double-compartment decline is divided by a steel divider. The upper compartment contains the coal conveyor belt, and the lower compartment is for transportation of men and materials. The single-compartment slope is used solely for intake ventilation through the mine fan. The double compartment slope is approximately 500 feet long driven on a decline of 14° to intersect the coal seam. The ventilation slope is driven on a decline of 16°. Bottom development was completed in the area where the two slopes intersected the coal. The West Mains were developed to a point where development of the South Submains could begin. When the South Submains were completed, the East Exhaust Portal was developed and the portal constructed. Development of the East Mains and the gateroads for longwall panels then began. Mining in the first • Permit Renewal #3 (Rev, 8/99) III-6