Methods of excavation and roof support used in some recently constructed tunnels

Author:	Polack, S. P.
Year:	1950
Document Type:	USBI
Issuing Agency:	U.S. Dept. of the Interior, Bureau of Mines,
SUDOC:	I 28.27:7568
Series:	Information circular / United States Department of the Interior, Bureau of Mines ;
Report Number:	7568
Subjects:	Mining engineering
	Tunneling--Equipment and supplies
Link:	https://hdl.handle.net/2027/mdp.39015078456053