130 TUNNELING 



machines. There are two turbines of 100 H. P. and 120 H. P. 

 taking water from a reservoir on the mountain slope, and 

 furnishing 220 H. P., which is distributed about as follows : 

 Boring-machines, 60 H. P. ; ventilation, 30 to 40 H. P. ; elec- 

 tric locomotives, 15 H. P. ; machine shop, 15 H. P. ; electric- 

 lighting dynamo, 25 H. P. ; electric drills, the surplus, or some 

 40 H. P. The boring-machines and electric drills will be 

 operated by the smaller 100 H. P. turbine. 



Sonnstein Tunnel. The Sonnstein tunnel in Germany is 

 particularly interesting because of the exclusive use of Brandt 

 rotary drills. The tunnel was driven through dolomite and 

 hard limestone by means of a drift and two side galleries. The 

 dimensions of the drift were 1\ x 7 ft. The power plant con- 

 sisted of two steam pressure pumps, one accumulator, and four 

 drills. The steam-boiler plant, hi addition to operating the 

 pumps, also supplied power for operating a rotary pump for 

 drainage and a blower for ventilation. The hydraulic pressure 

 required was 75 atmospheres in the dolomite, and from 85 to 

 100 atmospheres in the limestone. The drift was excavated 

 with five 3^ in. holes, one being placed at the center and 

 driven parallel to the axis of the tunnel, and four being placed 

 at the corners of a rectangle corresponding to the sides of the 

 drift, and driven at an angle diverging from the center hole. 

 The average depths of the holes were 4.3 ft., and the efficiency 

 of the drills was 1 in. per minute. One drill was employed 

 at each front, and was operated by a machinist and two helpers, 

 who worked eight-hour shifts, with a blast between shifts at 

 first, and later twelve-hour shifts, with a blast between shifts. 

 The 24 hours of the two shifts were divided as follows : boring 

 the holes, 10.7 hours; charging the holes, 1.1 hours; removing 

 the spoil, 11.7 hours; changing shifts, 0.5 hour. The average 

 progress per day for each machine was 6.7 ft. The total cost 

 of the plant was 817.450. 



St. Glair River Tunnel. The submarine double-track rail- 

 way tunnel under the St. Clair River for the Grand Trunk Ry., 



