DOT shield tunneling beneath residential districts in Nagoya City's subway construction

In Nagoya City, five subways with a combined length of 78.2 km are currently in service, and a new 11.3 km long line is currently under construction. The Double O Tube (DOT) shield tunneling method was adopted for seven out of the nine shield tunnel work areas, and excavation of four tunnel work areas has already been completed. The DOT method is a shield tunneling method for constructing a double-track tunnel of rational cross-sectional shape and has so far been used in four projects in Japan. This paper reports on the planning and construction of the Motoyama North Area, the longest tunnel section whose excavation began first and has already been completed. With an excavation length of 1,23 8.4 m, a maximum overburden depth of only 32.3 m and a longer-than-one-kilometer section that needs to be driven under a residential district, the tunnel section posed a challenge for the DOT method. A mucking system combining a continuous in-tunnel belt conveyor and a vertical belt conveyor was developed. The shield tunneling machine was launched on October 2, 2000, and the machine reached Motoyama Station on June 1, 2001.