Identifier: americanaunivers15beac (find matches)
Title: The Americana : a universal reference library, comprising the arts and sciences, literature, history, biograhy, geography, commerce, etc., of the world
Year: 1903 (1900s)
Authors: Beach, Frederick Converse, 1848-1918 Rines, George Edwin, 1860- Scientific American, inc
Subjects: Encyclopedias and dictionaries
Publisher: New York : Scientific American compiling dept.
Contributing Library: University of California Libraries
Digitizing Sponsor: Internet Archive

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ar feet has a diameter of 12feet, making 9,,^40 linear feet in all. The ma-terial penetrated was mostly sand and gravel,some of it being wet. The principal featureof the method is a wrought-iron cylinder ofone fourth inch plate and 6 feet in diameter,the axis of which corresponds with the axisof the tunnel. This small 6-foot heading orpilot is the first portion of the tunnel exca-vated. The front end of the pilot was carriedabout 30 feet ahead of the completed tunnelsection, allowing a lo-foot length of four-ringbrick masonry lining to be put in place, while15 to 20 fect_ of the pilot rested in unex-cavated material. As fast as excavation wasmade at the front end of the pilot, plateswere taken off the rear end which projectedinto the finished work and put in place at thefront end. In this manner the pilot wascarried ahead as fast as excavation could h?made. In this case the pilot was built ofone-fourth inch iron plates carrying 3-incnby 3-inch angles on their edges. The exca- TUNNELS.
Text Appearing After Image:
1. East Boston Tunnel, showing tuo uj.i.li sui.c: ini;i„^i-.i .Iriiis an.l earlli core. 2. East Boston Tunnel. Rear of roof shield. TUNNELS AND TUNNELING vation then made around the outside of thepilot was closely followed by radial strutswith one end supported against the pilot andthe other end carrying iron plates and laggingto protect the exposed face of the excavation.Iron plates were used over the crown of thefinished excavation, but were not carrieddown on the sides, although they could beso extended if desired. In this manner thecomplete tunnel was successfully excavatedand the material held back until the bricklining used in this case was in place. Allwork was done at ordinary atmospheric pres-sure. No other large work has been com-pleted by this method, although it possessesadvantages for many localities. Baltimore Belt Line Tunnel.— This double-track tunnel is a part of the double-trackline of railway in the city of Baltimore, Aid.,built for the Baltimore & Ohio and

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