Tunneling and underground transport : future developments in technology, economics, and policy : papers prepared for the conference held by the Macro-Engineering Research Group and the Center for Advanced Engineering Study of the Massachusetts Institute of Technology in cooperation with Stone and Webster Engineering Corporation, Arthur D. Little, Inc., and the American Society for Macro-Engineering, held April 24 and 25, 1985, at the Copley Plaza Hotel, Boston, Massachusetts / ceditor, Frank P. Davidson.