Figure ti. Hoosac 1 1 \\i i survey 

 crew at engineering office. Thehighesi 

 .11 , in. n \ hi the abi iveground and 

 underground survey work was required 

 in insiin- proper vertical and horizontal 

 alignment and meeting of the 



itely driven sections. (Photo cour- 

 • State library, Commonwealth of 

 Massa, husetts.) 



mounted on a carriage designed l>\ 1 inane. These 

 drove the holes lor the first blast in the center of the 

 heading in about six hours. The full width of the 

 heading, the 24-foot width of the tunnel, was then 

 drilled and blasted out in two more stages. As in 

 the early section, the benches to the rear were later 

 removed to the full-tunnel height of about 20 feet. 

 rhis operation is shown by a single drill (fig. 4) 

 mounted on a screw column. Three 8-hour shifts car- 

 ried the work forward: drilling occupied half the 

 time and half was spent in running the carriage back, 

 blasting, and mucking (clearing the broken rock). 



The tunnel's 1028-foot central shaft, completed 

 under the Shanloy contract in 1870 to provide two 

 additional work faces as well as a ventilation shaft is 

 shown at the far right side of this half of the model. 

 Completed so near the end of the project, only 15 

 percent of the tunnel was driven from the shaft. 



The enormous increase in rate of progress was not 

 due entirely to machine drilling. From the outset 

 of his jurisdiction. Doane undertook experiments with 

 explosives as well as drills, seeking an agent more 

 effective than black powder. In this ease, the need 

 for speed was not the sole stimulus. As the east and 

 west headings advanced further and further from the 

 portals, the problem of ventilation grew more acute, 

 and it became increasingly difficult to exhaust the 

 toxic fumes produced by the black powder blasts. 



In 1866, Doane imported from Europe a sample 

 of trinitroglycerine, the liquid explosive newly intro- 

 duced by Nobel, known in Europe as "glono'm oil" 



and in the United States as "nitroglycerine." It 

 already had acquired a fearsome reputation from its 

 tendency to decompose with he.it and aye and to 

 explode with or without the slightest pi 1 1\ . M .1 1 il I] 1 



Nevertheless, its tivmniilniK power and character- 

 istic oi almost complete smokelessness led Doane to 

 employ the chemist George W. Mowbray, who had 

 blasted for Drake in the Pennsylvania oil fields, to 

 develop techniques lor the bulk manufacture of the 

 new agent and for its safe employment in the tunnel. 

 M11vvl11.1v established a nml mi the mountain .mil 

 shortly developed a completely new blasting practice 

 based on the explosive. Its stability was greatly in- 

 creased by maintaining absolute purity in the manu- 

 facturing process. Freezint; the liquid to reduce its 

 sensitivity during transport to the headings, and 

 extreme caution in its handling further reduced the 

 hazard of its use. At the heading, the liquid was 

 poured into cylindrical cartridges lor placement in 

 the holes. As with the Burleigh drill, the general 

 adoption of nitroglycerine was immediate once iis 

 qualities had been demonstrated. The elicit on the 

 work was notable. Its explosive characteristics per- 

 mitted fewer blast holes over a given frontal at 

 wot king face, and at the same time it was capable 

 of effectively blowing from a deeper drill hole. 42 

 inches against 30 inches lor black powder, so that 

 under ideal conditions 40 percent more tunnel length 

 was advanced per cycle of operations. A new fuse 

 and a system of electric ignition were developed which 

 permitted simultaneous detonation and resulted in 



PAPER 41: TUNNEL ENGINEERING — A MUSEUM TREAI Ml \ I 



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