. Manual for railroad engineers and engineering students : containing the rules and tables needed for the location, construction, and equipment of railroads as built in the United States . ork 9inches thick. This brickwork was built upon an oak curb 9X3inches, from beneath which the earth was excavated, the curbbeing temporarily propped until underpinned by the brickworkbrought up from the second curb below. The greatest depth ofthe shafts was 344 feet, and the least 66 feet. The average rateof progress per day of 24 hours, from the commencement to thecompletion of each shaft, was 2 feet ; but
. Manual for railroad engineers and engineering students : containing the rules and tables needed for the location, construction, and equipment of railroads as built in the United States . ork 9inches thick. This brickwork was built upon an oak curb 9X3inches, from beneath which the earth was excavated, the curbbeing temporarily propped until underpinned by the brickworkbrought up from the second curb below. The greatest depth ofthe shafts was 344 feet, and the least 66 feet. The average rateof progress per day of 24 hours, from the commencement to thecompletion of each shaft, was 2 feet ; but counting only the daysupon which work was actually done, 3 feet 4 inches. The ma- ROCKWORK AND TUNNELLING. 93 terial was chiefly blue marl. The size of the heading was 5x3feet, the bottom being level with the topof the invert. The Almondsbury Tunnel, near Bristol, upon the Bristol andSouth Wales Junction Railway, Fig. 33, is 1221 yards long, 18feet 6 inches wide at the widest part, 17 feet wide at the road-bed, and 19 feet high. It was built for a single track ; the wholework being done by means of the shafts, of which there were five ;the deepest being 144, and the least 6y The Sydenham Tunnel, on the London, Chatham, and DoverRailway, is 2100 yards long, and is made through the Londonclay. It had seven shafts, varying from 50 to 186 feet in depth,and 9 feet internal diameter. Two only of these shafts wereintended to be left open permanently. The clay in which thiswork was executed, though yielding freely to the pick, afterwardsswelled, and crushed the masonry. The shafts were made 9 feetin diameter, but were afterwards pressed in so as to be hardlymore than 6. The headings were 4x6 feet, and were run for- 94 MANUAL. FOR RAILROAD ENGINEERS. ward at the top, and not the bottom, of the excavation. Theoriginal section is shown in Fig. 34. But the swelling of the clayso forced in the masonry that 6780 cubic yards of the side walland 2065 yards of the invert had to be rebui
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Keywords: ., bookcentury1800, bookdecade1880, bookpublisherbosto, bookyear1883
