■inure <i. I In. ,v\i 1 1 \m i . Flash- 

 powder photograph of Burleigh drills 

 at the working face, i Fholo cow 

 tnwealth of I ' 



require the machines to do too much .m<l the powder 

 too little of the work, thus contradicting the funda- 

 mental principles upon which all labor-saving 

 machinery is framed ... I could only look upon it 

 .is .) misapplication of mechanical genius." 



Latrobe stated the basic philosophy of rock-tunnel 

 work. No mechanical agent has ever been able to 

 improve upon the efficiency of explosives for the shat- 

 tering of rock. For this reason, the logical application 

 of machinery to tunneling was not in replacing or 

 altering the fundamental process itself, but in enabling 

 it to be conducted with greater speed by mechanically 

 drilling the blasting holes to receive the explosive. 



Vm.il work on the Hoosac Tunnel began at both 

 ends of the tunnel in about 1854, but without much 

 useful effeel until 1858 when a contracl was lei to 

 the renowned civil engineer and railroad builder. 

 Herman Haupt of Philadelphia. Haupt immediately 

 resumed investigations of improved tunneling meth- 

 ods, both lull-area machines and mechanical rock 

 drills. At this time mechanical rock-drill technology 

 was in a state beyond, but not far beyond, initial 

 experimentation. There existed one workable Ameri- 

 can machine, the Fowle drill, invented in 1851. It 

 w.is steam-driven, and had been used in quarry work, 

 although apparently not to any commercial extent. 



However, it was far too large and cumbersome to 

 find any possible application in tunneling. Never- 

 theless, it contained in its operating principle, the 

 seed of a practical rock drill in dut tin drill rod was 

 attached directly to and reciprocated by a double- 

 acting steam piston. A point of great importance 

 was the independence of its operation on gravity, 

 pei mitting drilling in -mv direction. 



While experimenting, Haupt drove the work on- 

 w.ud liv the classical methods, shown in the left-hand 

 section of the model (fig. 2). At the far right an 

 advance heading or adit is being formed by pick and 

 hammer work; this is then deepened into a top 

 heading with enough height to permit hammer 

 drilling, actually the basic tunneling operation. A 

 team is shown ••double jacking," i.e.. using tWO- 

 h mded hammers, the steel held by a third nun. 

 This was the most efficient of the several hand-drilling 

 methods. I he top-heading plan was followed so 

 that the bulk of the rock could be removed in the 

 I, ,iiii nl .i bottom bench, and the majority of drilling 

 would l>e downward, obviously the most effective 

 direction. Blasting was with black powder and its 

 commercial variants. Some liberty was taken in de- 

 picting these steps so that both operations might be 

 shown within the scope of the model: in practice 



PAPER 41: TUNNEL ENGINEERING A MUSEUM TREATMENT 



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