The Blasting of Rock in Mines, Quarries, Tunnels, Etc

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1898 edition. Excerpt: ...face, and fired simultaneously, the line of resistance being unity for one shothole, that we shall have But in the example we have N = 4, S: 29;; inches, m = 13% inches, /E = 14 inches, and d: 1% inch for the four longer holes, and 1% inches for the shorter holes; therefore, for the four holes Nos. 5, 6, 7, 8, we have Hence the line of resistance these four holes will break by their combined shearing action is 1 foot 9 inches X 0'9 = 1 foot 7 inches, which is less than for each fired singly, and their line of resistance, therefore, cannot exceed that corresponding to each, viz. 1 foot 9 inches. ' I On the other hand, if Nos. 1, 2, 3 and 4 were continued to meet Nos. 5, 6, 7, 8 we shouldl have four pairs of holes supporting each other when fired simultaneously, the relative power of each pair being 2X29: l-:58%: I_85 2(13+2 X 1%inch) 31% ' Consequently, for the four pairs of holes fired simultaneously, we shall have g = 1'85 X 0'9 = 1'67, that is, their combined shearing power is not equal to a greater line of resistance than 1 foot 9 inches 1'67 = 2 feet 11 inches, which is reduced by the small angle of the holes, namely, 20 with the line of resistance, to 2 feet 11 inches X '88 = 2 feet 7 inches, whereas the K actual line of "resistance is 3 feet 3 inches. If the line of resistance be I foot 9 inches for 1%.-inch holes, it will be 2 feet for the 1;;-inch diameter holes, Nos. I, 2, 3, 4, but as these holes are placed at a less angle than 90 with the line of resistance, they are only equal to a line of resistance of 2 feet ' 88 = I foot 9 inches. It will therefore be seen that there is a saving in the expense of boring by the shorter No. 1, 2, 3, 4 holes, and moreover the charge is better placed for doing the work, so that a...show more

Product details

• Paperback
• 189 x 246 x 2mm | 95g
• English
• Illustrations, black and white
• 1236941993
• 9781236941992