MAA GROUP Consulting Engineering

Common ducts along MRT lines

Installing common utility ducts along MRT lines during their construction is now a trend which avoids repeated excavations of the same road. MAA has designed two of these ducts, one along the Xinyi Line, one along the Songshan Line.

Xinyi Line

For the Xinyi Line, the same shield tunneling machine used for the metro line was used for the common utility duct, for the first time in Taiwan. The alignment and cross-sections of the common duct had to change frequently to avoid conflicts with existing utilities and to comply with the structures of the Xinyi Metro line. For example, the area of the future common duct near the World Trade Center station (R06) was already used by an existing sewage pipeline, a drainage box culvert and shafts of the Taipower company shield tunnels of the Xinyi Metro line. In this case, there was no available space to construct a shaft for the transition of the shield tunnel section to box culvert section over the station. Besides that, the heavy traffic was also a reason why using a shaft would be unacceptable. The shield tunnel machine had to stop ahead the station structure, and then enlarge the cross-section from inside out of the tunnel.

The common duct had a total length of 5,026 m of 2-3 cell duct, composed of a 3,134 m shield tunnel and a 1,892 m open cut box culvert. The construction was completed in 7 years along with the Xinyi subway line. The estimated total cost was about NTD 5.2 billion (approximately USD 153 million).

Songshan Line

In the case of the Songshan Line, the project included four underground subway stations, a twin shield tunnel with a total length of 2.9 km and a common duct system with a total length of 690 m.

Scope of work

• Common Duct Design using shield tunneling
• Interface Design