Author : Charles F. Gripper
Release : 2013-09
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Kind : eBook
Book Rating : 481/5 ( reviews)
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Book Synopsis Railway Tunnelling in Heavy Ground by : Charles F. Gripper
Download or read book Railway Tunnelling in Heavy Ground written by Charles F. Gripper. This book was released on 2013-09. Available in PDF, EPUB and Kindle. Book excerpt: 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. 1879 edition. Excerpt: ... CHAPTEB Y. os Jcxj-j Ayr-T-v?ntrv.--Excavatdtg and builling the brickwork of a Tunnel is done piece by piece, or in lengths, as they are termed; one length being mined and lined complete before any great amount of work is done in the next. The length of a length must be determined by the probable weight which will require supporting on the bars before the brickwork can be commenced and brought up; also upon the size and quality of the timber procurable for bars. A length is seldom more than 6 yards long, generally 5 yards, and in a heavy Tunnel 4 yards, and this sometimes has to be reduced to 3 yards in length. Let us suppose that lengths of 5 yards each can be worked, and that the Tunnel is rather heavy, and that drawing barn are required. In a light Tunnel all bars carrying the roof can be taken out as the brickwork is built up to them, and are called "taking-out bars," that is to say, that the ground is excavated and mined as nearly as can be to the exact shape of the extrados of tho brickwork, or lining, and therefore the back of the bars wipporting tho ground is just even with the back of the lining, excepting fivo or six of them at or about the crown of the arch, which aro kept up a few inches to compensate for settlement and witf; Mm Whiih aro built and the arch commenced, and when it coniim up to tho underside of the lowermost bar, it (the bar) is removed, and Ho on until all the bars are out and the arch keyed. It will ho obvious that when the arch is complete all but about BAES AND CILLS. 33 4 feet (measuring transversely), the crown, or top bar, must be taken out, and that the ground and incomplete arch are thus left without any support but that of the centres, and that the pressure or weight must be very Blight to allow of...