Optimization of tunnel pre-support-Softground NATM at Washingon, D.C. Metro's section F6b

摘要

Section F6b includes the construction of Congress Heights Station using cut and cover techniques and two 460 m long. single track tunnels that are the focus of this paper. The New Austrian Tunneling Method (NATM) was selected for tunnel construction because of (1) short length of tunnels, (2) short mobilization, and (3) the capability to mine from multiple headings. NATM tunneling started in October 1996 and the "hole through" in the IB tunnel was made in September 1997.