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 

 tunneled substance is of relatively small concern, 

 eclipsed by the problem of preventing the surrounding 

 material from collapsing into the bore. 



In one other principal respect does tunnel engi- 

 neering differ widely from its collateral branches of 

 civil engineering. Few other physical undertakings 

 are approached with anything like the uncertainty 

 attending a tunnel work. This is even more true in 

 mountain tunnels, for which test borings frequently 

 cannot be made to determine the nature of the 

 material and the geologic conditions which will be 

 encountered. 



The course of tunnel work is not subject to an overall 

 preliminary survey; the engineer is faced with not 

 only the inability to anticipate general contingencies 

 common to all engineering work, but with the pecu- 

 liar and often overwhelming unpredictability of the 

 very basis of his work. 



Subaqueous and soft-ground work on the other 

 hand, while still subject to many indeterminates, is 

 now far more predictable than during its early history, 

 simply because the nature of the adverse condition 

 prevailing eventually was understood to be quite 

 predictable. The steady pressures of earth and water 

 to refill the excavated area are today overcome with 

 relative ease and consistency by the tunneler. 



In tunneling as in no other branch of civil engineer- 

 ing did empiricism so long resist the advance of scien- 

 tific theory; in no other did the "practical engineer" 

 remain to such an extent the key figure in establishing 

 the success or failure of a project. The Hoosac Tun- 

 nel, after 25 years of legislative, financial, and techni- 

 cal difficulties, in 1875 was finally driven to successful 

 completion only by the efforts of a group who, while 



in the majority were trained civil engineers, were to 

 an even greater extent men of vast practical ability, 

 more at home in field than office. 



DeWitt C. Haskin (see p. 234), during the inquest 

 that followed the death of a number of men in a 

 blowout of his pneumatically driven Hudson River 

 Tunnel in 1880, stated in his own defense: "I am not 

 a scientific engineer, but a practical one ... I know 

 nothing of mathematics; in my experience I have 

 grasped such matters as a whole; I believe that the 

 study of mathematics in that kind of work [tunneling] 

 has a tendency to dwarf the mind rather than en- 

 lighten it . . . ."' An extreme attitude perhaps, and 

 one which by no means adds to Haskin's stature, but 

 a not unusual one in tunnel work at the time. It 

 would not of course be fair to imply that such men 

 as Herman Haupt, Brunei the elder, and Greathead 

 were not accomplished theoretical engineers. But it 

 was their innate ability to evaluate and control the 

 overlying physical conditions of the site and work that 

 made possible their significant contributions to the 

 development of tunnel engineering. 



Tunneling remained largely independent of the 

 realm of mathematical analysis long after the time 

 when all but the most insignificant engineering works 

 were designed by that means. Thus, as structural 

 engineering has advanced as the result of a flow of 

 new theoretical concepts, new, improved, and strength- 

 ened materials, and new methods of fastening, the 

 progress of tunnel engineering has been due more to 

 the continual refinement of constructional techniques. 



A NEW HALL OF CIVIL ENGINEERING 



In the Museum of History and Technology has 

 recently been established a Hall of Civil Engineering 



204 



BULLETIN 240: CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHNOLOGY 



