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Contribution's prom I The Museum of History and i c bnology. Papi.k 41 Tunnel Engineering—A Museum Treatmi \ i Robert M. Vogel lM'KOIU ( HON 2<H ROCK TLNNELING 206 SOFT-GROUND TUNNELING 215 BIBLIOGRAPHY 239 L-J( 527 67 - i lo break out ore i\ i[ \ i iu\s, chiseling i . Mining BY EARLY EiR' hi an 1/ usint; lire setting and hand and rock. Mill model \'\" scale. (Smithsonian photo 49260-H.) I Robert M. Vogel TUNNEL ENGINEERING- A MUSEUM TREATMENT During the years from 1830 to 1900, extensive developments took place in the field of tunneling, which today is an important, firmly established branch of civil engineering. This paper offers a picture of its growth from the historical standpoint, based on a series of models constructed for the Hall of Civil Engineering in the new Museum of History and Technology. The eight models described highlight the fundamental advances which have occurred between primitive nun's first system. /tic use of fire for excavating rock in mining, and the use in combination of com- pressed air, an iron lining, and a movable shield in .1 subaqueous tunnel .it the end of the 19th century. The Author: Robert M. Vogel is curator of heavy machinery and civil engineering, in the Smithsonian Institution s Museum of History and Technology. Introduction tunnels the utility of the "structure" is derived not from the bringing together of elements but from the I is naturally existing material 1 1 1' .1 In 'K portion of Willi FEW XI I I' '\s. civil ENG1N1 kim. non of one in which the ultimate goal i^ tin- assemblage of from another to permit passaue through .1 former materials into a useful structural form according barrier. scientifically derived plan which is based on various In tunneling hard, firm rock, this is practically natural and man-imposed conditions. This is true the entire compass of the work: breaking away the whether the result he. for example, a dam. a building, rock from the mother mass. and. coineidcntly. re- a bridge, or even the fixed plant of a railroad. How- moving it from the workings. The opposite extreme ever, one principal branch of the field is based upon in conditions is met in the soft-ground tunnel, driven an entirely different concept. In the engineering of through material incapable of supporting itself above PAPER 41: TUNNEL ENGINEERING—A MUSEUM Tkl \l\ll\l 203 — Tunnel. Method of working early sections of the project; blast holes drilled by hand jacking. MHT model }i" scale. (Smithsonian photo 49260-L.) the tunnel opening. Here, the excavation of the in the majority were trained civil engineers, were to tunneled substance is of relatively small concern, an even greater extent men of vast practical ability, eclipsed by the problem of preventing the surrounding more at home in field than office. material from collapsing into the bore. DeWitt C. Haskin (see p. 234), during the inquest In one other principal respect does tunnel engi- that followed the death of a number of men in a neering differ widely from its collateral branches of blowout of his pneumatically driven Hudson River civil engineering. Few other physical undertakings Tunnel in 1880, stated in his own defense: "I am not are approached with anything like the uncertainty a scientific engineer, but a practical one ... I know attending a tunnel work. This is even more true in nothing of mathematics; in my experience I have mountain tunnels, for which test borings frequently grasped such matters as a whole; I believe that the cannot be made to determine the nature of the study of mathematics in that kind of work [tunneling] material and the geologic conditions which will be has a tendency to dwarf the mind rather than en- ."' encountered. lighten it . An extreme attitude perhaps, and The course of tunnel work is not subject to an overall one which by no means adds to Haskin's stature, but preliminary survey; the engineer is faced with not a not unusual one in tunnel work at the time. It only the inability to anticipate general contingencies would not of course be fair to imply that such men common to all engineering work, but with the pecu- as Herman Haupt, Brunei the elder, and Greathead liar and often overwhelming unpredictability of the were not accomplished theoretical engineers. But it very basis of his work. was their innate ability to evaluate and control the Subaqueous and soft-ground work on the other overlying physical conditions of the site and work that hand, while still subject to many indeterminates, is made possible their significant contributions to the now far more predictable than during its early history, development of tunnel engineering. simply because the nature of the adverse condition Tunneling remained largely independent of the prevailing eventually was understood to be quite realm of mathematical analysis long after the time predictable. The steady pressures of earth and water when all but the most insignificant engineering works to refill the excavated area are today overcome with were designed by that means. Thus, as structural relative ease and consistency by the tunneler. engineering has advanced as the result of a flow of In tunneling as in no other branch of civil engineer- new theoretical concepts, new, improved, and strength- ing did empiricism so long resist the advance of scien- ened materials, and new methods of fastening, the tific theory; in no other did the "practical engineer" progress of tunnel engineering has been due more to remain to such an extent the key figure in establishing the continual refinement of constructional techniques. the success or failure of a project. The Hoosac Tun- A HALL OF CIVIL ENGINEERING nel, after 25 years of legislative, financial, and techni- NEW cal difficulties, in 1875 was finally driven to successful In the Museum of History and Technology has completion only by the efforts of a group who, while recently been established a Hall of Civil Engineering 204 BULLETIN 240: CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHNOLOGY Figun ; Hoosac h\\n Workinc oi later stages with Burleigh pneumatic drills mounted on car- riages. The bottom heading is being drilled in preparation for blasting out with nitroglycerine. Mill i }>" scale. (Smithsonian photo $260 M in which the engineering of tunnels is comprehen- tion hi one. Models of these works form the basis of sively treated from the historical standpoint —some- the exhibit. No effort was made to restrict the work in thing nol previously done in an American museum. projei tson American soil. I his would, in i.n t. have 1 .ill i < lias impossible . The guiding precept of the exhibit not been to been quite 1 . urate pit hire Ol tunnel outline exhaustively the entire history of tunneling, technology was to be drawn; for as in virtually all but rather to show the fundamental advances which other areas of technology, the overall development in have 01 curred between primitive man's firsl systematic this held has been international. I he art of mining use "I fire for excavating rock in mining, and the use was first developed highl) in the Middle Ages in the in combination ol compressed air, iron lining, and tnic states; the tunnel shu-ld was invented by movable shield in a subaqueous tunnel at the end of .1 Frenchman residing in England, and the use of the l''lh century. This termination date was selected compressed air to exclude the water from subaqueous because it was during the period from about 1830 to tunnels was firsl introduced on a major work by an 1900 that the most concentrated development took American. In addition, the two main subdivisions, place, and during which tunneling became a firmly rock and soft-ground tunneling, are each intra established and important branch of civil engineering by a model not of an actual working, but of one and indeed, of modern civilization. The techniques typifying early classical methods which were in use ol present-da) tunneling are so fully related in cur- fol ' ' nturies until the comparatively recent develop- rent writing that it was deemed far more useful to ment of mine efficient svvlems of earth Support uid devote the exhibit entirely to a segment of the field's lock breaking. Particular attention is given to accu- history which is less conmionlv treated. ol detail throughout the series of eight models; 1 he major advances, which have ahead) been original sources of descriptive and graphic information spoken of as being ones of technique rather than were used in their construction wherever possible. In theory, devolve quite naturally into two basic classi- all cases except the introductory model m the rock- fications: the one of supporting a mass of loose, tunneling series, reprcsentins; copper mining bv earl) unstable, pressure-exerting material soft-ground tun- civilizations, these sources were contemporary neling; and the diametrically opposite problem of accounts. separating rock from the basic mass when it is so The plan to use a uniform scale of reduction firm and solid that it can support its own overbearing throughout, in order to facilitate the viewers' inter- weight as an opening is forced through it rock, or pretation, unfortunately proved impractical, due to tunneling. the hard-ground greal difference in the amount of area I I" exhibit the sequence in a thorough manner. encompassed in different models, ami the necessity inviting and capable of easy and correct interpreta- that the cases holding them be of uniform height. The tion by the nonprofessional viewer, models offered related models of the Broadway and Tower Subways the only logical means of presentation.