New tunnel-boring machine makes cutting corners perfectly sound

A fully assembled rectangular tunnel-boring machine inside the launch shaft of Havelock MRT station.
A fully assembled rectangular tunnel-boring machine inside the launch shaft of Havelock MRT station.ST PHOTO: LIM SIN THAI
A miniature version of the rectangular tunnel-boring machine.
A miniature version of the rectangular tunnel-boring machine.ST PHOTO: LIM SIN THAI

SINGAPORE -The Land Transport Authority has become the first to use a rectangular tunnel-boring machine here, paving the way for future rail and road projects which could be speedier, cleaner and significantly less disruptive.

The first rectangular tunnel-boring machine - which excavates rectangular instead of circular tunnels -was deployed on May 11 for an underpass at the MRT Thomson-East Coast Line's Havelock MRT station.

Using a set of six cutter heads, the machine supplied by China Railway Engineering Equipment Group has since completed about 20 per cent of the 150m underground pedestrian walkway that goes under Zion Road to give commuters of the future line easy access to current and future developments in the area.

This new construction method is four times the cost of a cut-and-cover method, but LTA project director Henry Foo said it saves time, manpower and is far less disruptive.

A cut-and-cover method would involve multiple diversions to road and human traffic above ground, is dustier and noisier, and would have taken much longer.

With the new method, the underpass will be completed in "six to eight months", instead of "three to four years" with the cut-and-cover method -which involves excavating deep trenches along the entire stretch of the underpass.

The underpass is constructed under sections of Zion Road, Havelock Road and Ganges Avenue.

Mr Foo said: "It is hard for people to appreciate the benefits of this new method if we don't tell them about the long roundabout way pedestrians will have to walk if we had used the cut-and-cover, the several stages of road diversion, and the noise and dust residents in the nearby HDB blocks have to bear with."

Mr Foo said rectangular tunnel-boring machines are used extensively in China, where they are employed not only for underpasses but for underground roads too.

The unique machine - the first of its kind in Singapore - will be moved to the Thomson-East Coast Line's Stevens interchange station for another underpass that goes under the Bukit Timah canal.

In future, larger machines may be used to build MRT lines here. If so, such a machine would be able to bore a box tunnel large enough to accommodate two train tunnels as well as stations - significantly shortening the completion time of a new rail project and reducing disruption to the public.