The Keio Line starting at Shinjuku is an important part of the main artery in the Tokyo Metropolis rail transportation network with daily passengers of 1.69 million and with its operating length of 84.7 km in the western district of Tokyo and the northern district of Kanagawa.

To mitigate traffic congestions as well as to avoid potential traffic accidents due to surface crossings, a 3.7 km long underground double-track railroad project was planned and has been under construction with stations by cut-and-cover method and tracks in-between by EPB shield tunneling method.

The paper introduces special features of the shield tunneling such as:

1)Establishment and control of tunnel face pressure as well as measurement of excavated soils weight and volume to maintain strict tunnel face stability and to minimize settlements of the overlying tracks all along the tunnel alignment, resulting in no disruptions to the existing railroad operations.
2)Smooth and stable discharge of excavated soils from pressure chamber by controlling face
pressure and selecting most suitable liquefizer and its injection volume to bore through gravelly soils with boulders as large as 300 mm in diameter, and with seasonal changes of groundwater level.
3)Minimizing influences of the in-bound tunneling on the preceding out-bound tunnel lining with only
400 mm intervals.