In Taiwan, the northern city of Taoyuan, near the capital Taipei, has seen rapid development in its commercial and industrial sectors as well as population growth over the last few decades. A strategic transport improvement initiative is being implemented, involving a major expansion of its mass transit network and including much underground construction.

For the Taoyuan’s Mass Rapid Transit (MRT) network, a number of metro lines are in planning and development – the priority line being the 27.8km-long Green Line, which will run approximately south-north through the centre of the growing city. The line has about 40% state funding, 40% from revenue-based, and about 20% from the city.

Green Line

The Green Line is to have 21 stations, 10 of them underground. It is due to be completed in 2026.

In the south, the line starts in the Bade District’s urban enlargement area with two surface stations (G01, G02) before running underground through the middle of the city with the 10 sub-surface stations (G03-G12) and then the alignment is above ground with the remaining nine stations, close to the airport.

At the northern above-ground stretch the lines branches into two sections, both connecting to the city’s Blue Line (which is part of Taoyuan Airport MRT, running from the Taipei).

For the construction works of stations and twin tube tunnels, Contract Lot GC03 will be undertaken in two sections: the north, 2.3km-long portion (stations G10-G12); and, the 2.6km-long stretch immediately south (G07-G09).

The contractor is Futsu-Obayashi-Cec Joint Venture (FOC JV).

The stations are Taoyuan main rail station (G07), Yong’he Market station (G08), Minguang Road station (G09), Daxing West Road Intersection station (G10), Taoyuan P Arts Center (G11), and Nankan Bus station (G12).

For the tunnelling work on Lot GC03, upon passing their Factory Acceptance Tests (FAT), Terratec has delivered four machines to FOC JV. There were two 6.24m-diameter TBMs supplied for the north section, and two 8.38m-diameter machines for the south section. The machines were supplied on behalf of Terratec’s group company JIMT.

The first two machines passed their FATs in 2021, the larger TBMs most recently.

Geology along the contract tunnel alignment includes sandstone and boulders. The two 8.38m-diameter EPBMs have robust spoke type with outer ring cutterheads and discharge large boulders through a ribbon-type screw conveyor.

Other features include VFD electric cutterhead drives, disc roller cutters and reinforced cutting tools for gravel layers, high torque screw conveyors, active articulation systems and state-of-the-art guidance and control systems.

Tunnel lining is 1200mm-wide by 350mm-thick reinforced concrete segmental rings (6+key). Muck cars will be used.

The two TBMs are to bore parallel southbound drives from the launch shaft near Daxing West Road Intersection station (G10) and finish at Taoyuan main rail station (G07). Tunnelling is expected to start in the second half of 2023.

A total of seven TBMs for the project has come from Terratec/JIMT – five manufactured in Terratec’s factory with key components from Japan. JIMT was formed by merging the TBM divisions of Japanese groups IHI, Mitsubishi Heavy Industries and JFE Engineering. Terratec has been a member of JIMT since 2018.

Green Line Extension

At the south end of the Green Line, a future extension is being planned to run northwest to also connect with the Blue Line – ending at Zhongli main rail station; the Blue Line’s route is in a semi-circle around the north of Taoyuan.

From the end of the Green Line, at G01 surface station, the extension will run with five new stations (four underground (GE02-GE05)) to the Blue Line.

Taoyuan Rail Underground

The city also plans a major underground link between mainline rail terminals at Taoyuan station and Zhongli station. The link will run across the part of the middle of the city, and will intersect with the Green Line, at the G07 underground station – at also meet the end of the Green Line Extension.

Sanying Line Extension

Another linking line, this one is relatively short – only 3.9km, and underground in part – to tie together the Taoyuan network with that of Taipei, which extends very near to the city.

The Sanying Line is located in Yingge District, New Taipei City and a short extension would take it near to the Green Line’s at station G04. There, its station would be the LB14 underground station.