NK TI NN F.I.I N<; 



219 



was accomplished by dividing the shield transversely, separat- 

 ing the tail-end section, or that which overlaps the tunnel, from 

 the cutting-edge section containing the working chaml>ers. 

 These two sections were, of course, circular, 11 ft. g in. out- 

 side diameter. The tail end section was 3 ft. 6 ins. long, ar.d 

 the cutting-edge section 3 ft. 8 ins. long. Both of tl c. c o 

 sections were a:_ r ain divided, longitudinally, into four quadrants. 

 The outside shell, in both tail-end and cutting-edge sections, 

 was made up of one i in. and one | in. steel plates riveted 

 together; and at the four quadrant joints, there were -in. butt- 

 straps 12 ins. wide running the whole 

 length of the shield and uniting the 

 quadrants and the two sections. The 

 middle diaphragm, separating the 

 cutting-edge and tail-end sections, 

 was made of two plates, one riveted 

 to each of the two sections, and these 

 two plates bolted together with the 

 butt-straps united the sections. The 

 cutting-edge section contained two 

 platforms, one vertical and one hori- 

 zontal, of the same length as the 

 section. 



To erect this shield the only rivet- 

 ing necessary was at the four butt- 



strap joints in the tail-end section, where it was necessary to 

 preserve a flush surface on both sides of the outer shell. In 

 tbe cutting-edge ]art countersunk bolts were used through the 

 biitt-strai>s. About 5>S() ;-in. bolts and 100 rivets were used to 

 the shield. T\v dnors closing cadi of the four working 

 chaml>ers were hung on the vertical platform, and were pro- 

 vided with fastenings so that the whole face could be easily 

 oiotecL 



T" drive the shield 1- -Vin. hydraulic jacks were used, 

 designed for a working pressure of 5,000 Ibs. per sq. in., or 



Fio. 118. Election and Section 

 of Hydraulic Jack, Kut Kiver 

 OM Tunnel. 



