Coal mining in Illinois . ^ CO x^ 5 CM CM CM CM cm CM* cm CO On l>» r^ LO LO nO o a en n a sO vO CM ,£> o ?H en o t> £> |- bfi rt 01 [> CD-1 200 COAL MINING INVESTIGATIONS With but few exceptions the shafts sunk prior to 1913 aretimber lined. The development of the cement gun has pro-vided a means of fireproofing these shafts. The timber lining-can be given a concrete cover by means of the cement gunwhich sprays under air pressure of about 40 pounds persquare inch a cement mortar composed of about 1 part Port-land cement and 3 parts coarse sharp sand. At a shaft inDistrict VI th
Coal mining in Illinois . ^ CO x^ 5 CM CM CM CM cm CM* cm CO On l>» r^ LO LO nO o a en n a sO vO CM ,£> o ?H en o t> £> |- bfi rt 01 [> CD-1 200 COAL MINING INVESTIGATIONS With but few exceptions the shafts sunk prior to 1913 aretimber lined. The development of the cement gun has pro-vided a means of fireproofing these shafts. The timber lining-can be given a concrete cover by means of the cement gunwhich sprays under air pressure of about 40 pounds persquare inch a cement mortar composed of about 1 part Port-land cement and 3 parts coarse sharp sand. At a shaft inDistrict VI the timber lining was covered with a 2-inch layerof Gunite, as concrete applied by this method is called, atthe rate of 190 square yards in 8 hours. The walls of theshaft were first covered with American Steel and Wire Com-panys No. 7A netting as a reinforcement for the Fig. 61. Circular hoisting shaft Gunite sets in 2% to 3 hours. The cost of application variesfrom 16 to 24 cents per square foot depending largely uponthe amount of water the shaft makes. With a dry andsmooth timber lining the work should average about 20 centsper square foot. The shafts of all mines in Illinois are of moderate size,the largest at the mines examined being 11 by 22 feet. Noserious difficulties have been encountered in sinking flow has never been large. At one mine in District VIa considerable body of quicksand necessitated a reduction ofshaft size but in general shaft sinking is comparatively cheapand speedy.
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectcoalmin, bookyear1915
