COST OF EXCAVATION AND TIME REQUIIIKD 



Mr. Sejourne", a French engineer, who has been connected 

 with the construction of numerous tunnels by the Belgian 

 method where he was in position to secure comparative figures, 

 has given the following rules for calculating the cost of 

 tunnels. Assuming A to represent the cost of excavating a 

 cu. yd. in the open air, the cost of excavating tin- same 

 quantity underground in driving headings will l>e from '.' .1 t> 

 11^4, and in enlarging the profile it will be about 5 ^4. Tin- 

 cost of constructing single-track tunnels varies with the thick- 

 ness of the lining, and may be calculated by the following 

 formulas : 



Without lining, C = 5. 5 A. 



With roof arch only, C = 6.4 + 6.4 A. 



With lining 18 in. thick, C = 9.4 + 7A. 



With lining 2 ft. thick, C = 11 + 8 A. 



In these formulas C is the cost per cu. yd. of excavation, 



including the masonrv. For <luiil>lc-track tunnels the amounts 

 jriven 1>\ the ahove formulas may be used by reducing them 

 ;I!H nit 71- ',' or s 



Tin- second method of estimating the Cost of tunnel \\ork 

 consists in assuming as a unit the unit cost of tunnels pre- 

 viously excavated under similar conditions. Mr. La Dame 

 _ri\es the following unit prices for a number of tunnels driven 

 through different materials: 



