Laserfiche WebLink
<br />4.2.2 Rnom-and-Pillar Minin¢ Room-and-pillar mining with continuous miners is a standazd <br />method of underground coal mining in the United States. This mining system can easily adjust to <br />changes in the geological and physical conditions of the mine. It is possible to exclude undesvable <br />sections of the deposit, negotiate structurally disturbed areas of the mine, and adapt to variations of the <br />' coal seam. The equipment can be easily moved to different locations in the section and the overall <br />system is only minimally affected by a stoppage of any one unit. Although this system is generally <br />more hazardous and more expensive to operate than a longwall system, it is this flexibility that has <br />' made continuous mining machines the mainstay of underground coal production in this country. In the <br />Deserado Mine the overall coal reserve recovery from room-and-pillar panel mining is estimated to <br />' average about 70 percent because all of the pillars cannot at all times be safely extracted. It is estimated <br />that a continuous miner will produce between 600 to 800 tons per 8-hour shifr depending upon specific <br />mining conditions. Coal recovery from areas not suited for longwall mining will be accomplished with <br />room-and-pillaz mining wherever ecomically and technically feasible. <br />Atypical room-and-pillar panel will be 1000 feet wide, of varying length and surrounded by 200-foot <br />thick barrier pillars. The panel will be developed by 20-foot wide entries. The pillaz size during <br />development will vary from 40'x40' to 50'x50'. The pillars will be partially extracted during retreat. <br />The final pillar size will vary from 32'x32' to 42'x42'. Figure 4-2 shows a typical room-and-pillaz <br />panel. <br />4Z.3 inngwall Minin¢ I.ongwall mining is relatively new in the United States. It has gained great <br />acceptance because of its three apparent advantages: <br />' 1) high recovery of the reserve <br />' 2) high productivity <br />3) better safety record <br />' In longwall mining, coal is extracted from panels that are thousands of feet long and hundreds of feet <br />wide. The shearer cuts coal as it passes back and forth across the longwall face. The coal falls onto <br />' a face conveyor, consisting of flexible steel pans, which transfers the coal away from the face to the <br />gate conveyor. The roof along the face is supported by hydraulic shields that sit behind the face <br />conveyor. As the shearer passes across the face, the face conveyor is advanced, and then the shields <br />' are advanced up to the conveyor. As the shields are advanced, the roof behind them is allowed to cave. <br />This cycle is then repeated each time the shearer passes across the face for the entire length of the <br />longwall panel. <br />21 <br /> <br />