Coal mining in Illinois . I I Fig. 15. Shearing the ribs in District VII at intervals of 500 to 600 feet along the cross-entries pairsof room-entries, often called panel entries, are tinned off at aright angle to the cross-entries. The solid pillar of coal be-tween the cross-entry and the first room, called the cross-barrier pillar, in Illinois varies in width from 20 to 150 feetand averages 56. The main barrier-pillar which is the coalleft between the main entry and the ends of the rooms turnedoff those room-entries which are nearest to the main entry,varies in width from 20 to 150 feet, aver
Coal mining in Illinois . I I Fig. 15. Shearing the ribs in District VII at intervals of 500 to 600 feet along the cross-entries pairsof room-entries, often called panel entries, are tinned off at aright angle to the cross-entries. The solid pillar of coal be-tween the cross-entry and the first room, called the cross-barrier pillar, in Illinois varies in width from 20 to 150 feetand averages 56. The main barrier-pillar which is the coalleft between the main entry and the ends of the rooms turnedoff those room-entries which are nearest to the main entry,varies in width from 20 to 150 feet, averaging 68. The num-. Fig. 16. Plan of panel mine MINING PRACTICE 85 ber of rooms on a room-entry varies in Illinois from 12 to 35and averages 23. The obvions advantage of a true panel system is thateach panel is surrounded on all sides by a pillar of solid coaland is a separate unit in operation. A squeeze occurring inany panel is confined by the barrier pillars, if large ventilating current can be regulated so as to supply airaccording to the needs of each panel and pillar-drawing canbe more advantageously practiced, thus giving a higher coal-recovery. In Illinois some of the newer mines were opened on thepanel system and some of the older mines which had beenunsuccessful in preventing squeezes under the unmodifiedroom-and-pillar system have changed their system to are, however, only a few mines operating on a truepanel system with proper barrier pillars. In many mines nopanel is maintained but rooms are driven to hole through,the main barrier pillar is gouged, and the cross barrie
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectcoalmin, bookyear1915
