Engineering Wonders of the World
Volume I

THE RIVER TUNNELS OF NEW YORK CITY. 111 soil, but that the shield could force it aside, as a pointed pencil might be shoved into a mass of clay. The scheme was so successful that a simply phenomenal speed of progress was attained. On the best day, in fact, the shield advanced 62 feet in twenty-four hours. But even this was exceeded later on in the lower tunnels, where the record advance of 72 feet in one day was made by the same method. The south tunnel was “ holed through ” late in 1905. In the meantime other shields tf. Roof-Shield places the ■1. Main Tunnels driven-I-.. Cast-Iron Roof Plates 5. Platform Floor ’ Constructed' 4. Shell Removed and Columns and Cinders placed •3. Th/s Space excavated down to Platform Level Fig. 12.—CROSS-SECTION THROUGH STATION BETWEEN TWO TUNNEL TUBES, BUILT BY AN INGENIOUS NEW METHOD. (UPPER HUDSON TUNNELS, LAND SEC- TION.) 1. The two tunnels driven and lined. 2. Station roof section then tunnelled out by use of a small roof shield resting on the two tubes, and a cast-iron arched roof placed behind this shield. 3. The space under the roof excavated, down to the platform level. 4. The tunnel shell removed along the excavated space, and replaced by columns and girders to carry the roof of main and intermediate tunnels. 5. A concrete platform floor put down at the level of the car floor. A stairway up to the surface at one end of the platform completes the station. had been started landward from the New York shore shaft, to construct the land section of the tunnel railway system. Here sand was encountered, almost as dangerous and difficult as the river mud; and the work caused more anxiety, because it passed under the foundations of columns supporting an elevated railway, and under house founda- tions, and the like. An amusing incident occurred in this land work. The compressed air could not be retained at the shield with absolute tightness, but some constantly bubbled up through the sand. Where the shield passed under a house the air would filter up into the dwellings. In one case a sewing-party in . j An Amusing a basement room was sud- , ., Incident. denly terrified by seeing the carpet bulge upward as though the earth were rising, and then subside again, while a blast of air made itself felt. The people were unaware of the tunnel work going on under them, and did not know until afterwards that an usually large leak of air from the shield was the cause of this ghostly phenomenon. Of the many novel schemes worked out in building these tunnels, one example is pic- tured by our sketch (Fig. 12). It shows the strikingly simple method by which station platforms were constructed in the intermediate space of the pair of land tubes. THE LOWER HUDSON TUNNELS. About the time the old Hudson Tunnel was started toward completion, in 1903, there was coupled to it an enterprise for two tunnels under the Hudson some two miles farther south. These lower Hudson tunnels are now nearly finished. They start on the New Jersey shore in a solid rock excavation (Fig. 10), seventy feet below water, directly under the Pennsylvania Railroad train-shed at Jersey city, and thence diverge eastward, the north tube leading to Fulton Street, the south tube to Cortlandt Street, in New York. A cross- connection forms a terminal loop for the trains at the New York end ; while at the New Jersey end they turn northward by a land tunnel, and finally join the upper tunnels. The methods of working have been exactly the same as those used in the simultaneous work of the upper tunnels. The shields used are about 17 feet in diameter, and the cast- iron lining of the tunnels is 16 feet 7 inches outside ; but the north tube of the upper tunnels has a larger diameter, about 19 feet, on account of its connection with the old work. The New Jersey land tubes were also