TUNNELING 



CHAPTER XII. 



REPRESENTATIVE MECHANICAL INSTALLA- 

 TIONS FOR TUNNEL WORK. 



THE important role played by the power plant and other 

 mechanical installations in constructing tunnels through rock 

 has already been mentioned. In some methods of soft-ground 

 tunneling, and particularly in soft-ground subaqueous tunnel- 

 ing, it is also often necessary to employ a mechanical installa- 

 tion but slightly inferior in size and cost to those used in 

 tunneling rock. The general character of the mechanical 

 plant required for tunnel work has been described in another 

 chapter. It is 1 proposed to describe very briefly here a few 

 typical individual plants of this character, which will in some 

 respects give a better idea of this phase of tunnel work than 

 the more general descriptions. 



Rock Tunnels. The tunnels selected to illustrate the me- 

 chanical installations employed in tunneling through rock ore : 

 The Hoosac Tunnel, the Cascade Tunnel, the Niagara Falls 

 Power Tunnel, the Palisades Tunnel, the Croton Aqueduct 

 Tunnel, the Strickler Tunnel, in America, and the Graveholz 

 Tunnel and the Sonnstein Tunnel in Europe. In addition 

 there will be found in other chapters of this book a description 

 of the mechanical installation at the Busk tunnel and at the 

 St. Gothard and Simplon tunnels. 



Hoosac Tunnel. The Hoosac tunnel on the Fitchburg R.R: 

 in Massachusetts is 25,000 ft. long, and the longest tunnel in 

 America. The material through which the tunnel was driven 

 was chiefly hard granitic gneiss, conglomerate, and mica-schist 

 rock. The excavation was conducted from the entrances and 



