HOOSAC TUNNEL 



It was possible in the model series, without neglect- 

 ing any major advancement in the art of rock 

 tunneling, to complete the sequence of development 

 with only a single additional model. Many of the 

 greatest works of civil engineering have been those 

 concerned directly with transport, and hence are the 

 product of the present era, beginning in the early 

 19th century. The development of the ancient arts of 

 route location, bridge construction, and tunnel 

 driving received a powerful stimulation after 1800 

 under the impetus of the modern canal, highway, and, 

 especially, the railroad. 



The Hoosac Tunnel, driven through Hoosac 

 Mountain in the very northwest corner of Massa- 

 chusetts between 1851 and 1875, was the first major 

 tunneling work in the United States. Its importance 

 is due not so much to this as to its being literally 

 the fountainhead of modern rock-tunneling tech- 

 nology. The remarkable thing is that the work was 

 begun using methods of driving almost unchanged 

 during centuries previous, and was completed twenty 

 years later by techniques which were, for the day, 

 almost totally mechanized. The basic pattern of 

 operation set at Hoosac, using pneumatic rock drills 

 and efficient explosives, remains practically unchanged 

 today. 



The general history of the Hoosac project is so 

 thoroughly recorded that the briefest outline of its 

 political aspects will suffice here. Hoosac Mountain 

 was the chief obstacle in the path of a railroad pro- 

 jected between Greenfield, Massachusetts, and Troy, 

 New York. The line was launched by a group of 

 Boston merchants to provide a direct route to the 

 rapidly developing West, in competition with the 

 coastal routes via New York. The only route 

 economically reasonable included a tunnel of nearly 

 five miles through the mountain — a length absolutely 

 without precedent, and an immense undertaking in 

 view of the relatively primitive rock-working methods 

 then available. 



The bore's great length and the desire for rapid 

 exploitation inspired innovation from the outset of 

 the work. The earliest attempts at mechanization, 

 although ineffectual and without influence on tunnel 

 engineering until many years later, are of interest. 

 These took the form of several experimental machines 

 ut the "lull area" t\ pe, intended to excavate the entire 

 face of the work in a single operation by cutting one 

 or more concentric grooves in the rock. The rock 



Figure 5. — Burleigh rock drill, improved model 

 of about 1870, mounted on frame for surface work. 

 (Catalog and price list: The Burleigh Rock Drill 

 Company, 1876.) 



remaining between the grooves was to be blasted out. 

 The first such machine tested succeeded in boring a 

 24-foot diameter opening for 10 feet before its total 

 failure. Several later machines proved of equal 

 merit. 1 ' It was the Baltimore and Ohio's eminent 

 chief engineer, Benjamin H. Latrobe, who in his 

 Report on the Hoosac Tunnel (Baltimore, Oct. 1, 1862, 

 p. 125) stated that such apparatus contained in its 

 own structure the elements of failure, ". . . as they 



-' In 1952 a successful machine was developed on this plan, 

 with hardened rollers on a revolving cutting head for disinte- 

 grating the rock. The idea is basically sound, possessing ad- 

 vantages in certain situations over conventional drilling and 

 blasting systems. 



208 



bumf.iin 2-ln: con 1 Rim 1 kins from the museum of history \nd technology 



