Tunnel Boring Machine Selection for the Baltimore Red Line Downtown Tunnel

摘要

The Baltimore Red Line Project by the Maryland Transit Administration (MTA) involves designrnand construction of a three mile long tunnel through downtown Baltimore, enabling light rail service betweenrnresidential and business areas. This paper focuses on the considerations for the selection of an appropriaternTunnel Boring Machine methodology for the Downtown Tunnel contract procurement. Design challengesrnof tunneling beneath downtown Baltimore include: a tight right-of-way; close proximity to historic andrnmodern high-rise buildings; pre-existing underground tunnels and utilities; and extremely challenging groundrnconditions consisting of soil and rock in both full-face and mixed-face conditions. A comprehensive assessmentrnand comparison of state-of-the-art tunnel face support, including innovative hybrid machine techniques withrnearth pressure balance, slurry face control and open-mode capabilities was performed to determine the mostrnsuitable approach for the project.