TUNNELING 



CHAPTER I 



PRELIMINARY CONSIDERATIONS. CHOICE BE- 



TWEEN A TUNNEL AND OPEN CUT. 



GEOLOGICAL SURVEYS 



CHOICE BETWEEN A TUNNEL AND AN OPEN CUT 



WHEN a railway line is to be carried across a range of 

 mountains or hills, the first question which arises is whether 

 it is better to construct a tunnel or to make such a detour ;is 

 will enable the obstruction to be passed with ordinary surface 

 construction. The answer to this question depends \\\*m the, 

 comparative cost of construction and maintenance, and upon 

 the relative commercial and structural advantages and disad- 

 vantages of the two methods. In favor of the OJKMI road there 

 are its smaller cost and the decreased time required in it,s ((in- 

 struction. These mean that less capital will be required, and 

 that the road will sooner be able to earn something for its 

 builders. Against the open road there are : its greater length 

 and consequently its heavier running ex]*'ii8es; the greater 

 amount of rolling-stock required to ojienite it; the heavy ex- 

 pense of maintaining a mountain road; and the necessity <-f 

 employing larger loeoi with the increased expenses which 



they entail. In favor of the tunnel there are: the shortening 

 of the road, with the consequent decrease in the operating 

 expenses and amount of rolling-stock required; the smaller cost 



