-. V • 



Figure 14 YVksi portai 01 1 1 < •. j-, \. I rxxr.i before 



completion, 1868, showing six rings of lining I > 1 i * k. 

 {Photo courtesy of State Library • \i husetts.) 



.1 degree of effectiveness impossible with the powder 

 train and cord fusing used with the black powder. 

 < )\ er .1 million pounds of nitroglycerine were pro- 

 duced In Mowbray between 1866 and completion oi 

 the tunnel. 



When the Shanleys took the work over in 1868, 

 following political difficulties attending operation l>\ 

 the St. ite. the period of experimentation was over. 

 The tunnel was being advanced by totally modern 

 methods, and to the present day the overall concepts 

 have rem. lined fundamentally unaltered: the Bur- 

 leigh piston drill has been replaced by the lighter 

 hammer drill; the Doane drill carriage by the more 

 flexible "jumbo"; nitroglycerine by its more stable 

 descendant dynamite and its alternatives; and static- 

 electric blasting machines by more dependable 

 magnetoelectric. But these are all in the nature of 

 improvements, not innovations. 



Unlike the preceding model, there was Liood docu- 

 mentation for this one. Also, the Hoosa< was appar- 

 .iit 1 \ the firsl American tunnel to be well recorded 

 photographically. Earl) flashlight views exist of the 

 drills working at the heading Mi'-;. 6) as well as of the 

 portals, the winding and pumping works at the cen- 

 tral shaft, and much of the machinery and associated 



aspei ts 0! the projei t. I hese and copies ol drawings 

 of much of Doane's experimental apparatus, a rare 

 technological record, are preserved at the Massachu- 

 setts state Library. 



Soft-Ground Tunneling 



v,, great is the difference between hard-rock and 

 soft-ground tunneling that the) constitute two almost 

 separate brain lies ol the held. In penetrating ground 

 lacking the firmness or cohesion to support itsell above 

 an opei.ii •_', the n iner's . hiel concern is not that ol 

 it 11 o\ ing the n at< 1 tal, but oi preventing its collapse 

 u, 1 o In- 1 xcavation. I he primitive methods depend- 

 ing upon brute strength and direct application ol fire 



and hi m lone were suitable tor ass.iuli on roik. 



bm lacked the artifice needed for delving into less 

 stable material. Roman engineers were accomplished 

 in spanning subterranean ways with masonr) arches, 



but apparently most of their work was done b\ cut- 

 and-covei methods rather than b) actual mining. 



\oi mini the Middle Ages did the skill of effectivel) 

 working openings in soft ground develop, and not 

 until the Renaissance was this development so con- 

 sistently successful that it could l».- considered a 

 science. 



RENAISSANCE \1l\l\t. 



From the earliest periods of rock working, the quest 

 for minerals and metals was the primary force that 

 drove men underground. It was the technolog) ol 

 mining, the product of slow evolution over the 

 centuries, that became the technology of the earl) 

 tunnel, with no significant modification except in 

 size of workings. 



Every aspect of 16th-century mining is definitively 

 detailed in Georgius Agricola's remarkable I)> >> 

 \\ ,. first published in Basel in 1556. During 



its time of active influence, which extended for two 



centuries, it served as the authoritative work on the 

 subject. It remains today an unparalli led earl) record 

 of an entire branch of technology. I he superb 

 woodcuts of mine workings and tools in themselves 

 constitute a precise description of the techniques ol 



the period, and provided an ideal Source of informa- 

 tion upon which to base the first model in the soft- 

 gl ound series. 



The model, representing a typical European mine. 

 demonstrates the early use of timber frames or 

 "sets'" to support the soft material of the walls and roof. 

 In areas of only moderate instability, the sets alone 



PAPER 41: TUNNEL ENGINEERING — A MUSEUM TREATMEN1 



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