Sl'l.rlAL TBKACHEHOUS GKOl M MKTHoIi 



171 



previously described. The upper half of the section being ex- 

 cavated, as in the Belgian method, the system of hauling with 

 inclined planes to the tunnel floor below, which is a character- 

 istic of that method, may be employed. It is the more usual 



Pio. 97. Sketch Showing Longitudinal Section of a Tunnel under Construction, 



Italian Method. 







practice, however, since the excavation is carried so little a dis- 

 tance ahead and progresses so slowly, to handle the spoil from 

 the upper part of the section by wheelbarrows which dump it 

 into the curs running on the tunnel floor below. Hand labor 

 is also used to raise the construction 

 materials used in building the upper Mo- 

 tion. The tracks on the tunnel floor, 

 besides extending to the front of the ad- 

 vanced bottom center drift, have right and 

 left switches to be employed in removing 

 the refilling in parts No. 2, the spoil from 

 the upper part of the section, and the . 



Pio. 96. Sketch Showing 



material of part No. 7. Fig. 97 is a longi- 

 tudinal section showing the plan of exra- 

 vation and strutting adopted with the Italian method. 



Modifications. It often happens that the filling placed be* 

 tween the side walls and the planking, which is practically the 

 space comprised by parU No. 2, is not sufficient to resist the 

 inuanl pressure of the walls, and they tip inward. In these 

 cases a common ex [Client is to substitute for the earth filling 



Sequence of Excavation. 

 Htazxa Tunnel. 



