56 



TUNM-:LIN<; 



FIG. 35. Iron Dump-Car for 

 Tunnel Work. 



wooden platform mounted on tracks, and they are usually em- 

 ployed for the transportation of timber, ties, etc. Dump-cars 

 are used in greater numbers in tunnel work than any other 

 form. Fig. 35 shows a dump-car of metal construction, and 



Fig. 36 one constructed with a metal 

 under-frame uid wooden box. These 

 cars are made to run on narrow-gauge 

 tracks, and usually have a capacity of 

 about one to one and one-half cubic 

 yards. Box-cars are more extensively 

 employed in Europe for tunnel work 

 than in America. Fig. 37 shows a 

 typical European box-car for tunnel 

 work. It is made either to run on narrow-gauge or standard- 

 gauge tracks. 



It is usually desirable in tunnel work to employ cars of 

 different forms for different parts of the work. In rock 

 tunnels it is a common practice to use narrow-gauge cars of 

 small size in the headings, and 

 larger, broad-gauge cars for the 

 enlargement of the profile. 

 Where narrow-gauge cars are 

 employed for all purposes, it will 

 also be found more convenient 

 to use platform-cars for handling 

 the construction material, and 

 dump-cars for removing the spoil. 

 The extent to which it is desir- 

 able tO USe Cars Of different forms Fro. 36.- Wooden Pump-Car for Tunrel 



Work. 



will depend upon the character 



and conditions of the work, and particularly upon how far it is 



possible to install the permanent track. 



As a general rule, it is considered preferable to lay the 

 permanent tracks at once, and do all the hauling upon them, 

 so that as soon as the tunnel is completed, trains may pass 



