SMRT renews North-South, East-West lines' ageing track beds

Checks show more locations require renewal, prompting pre-emptive plans

- Vanessa Paige Chelvan Correspondent

old ballast in between sleepers at Bishan MRT station in the early hours of Dec 11, as part of a process to renew worn-out ballast to ensure rail reliability. Renewing ballast involves intensive labour. It takes 10 to 12 workers roughly three hours to replace the stones on an up to 5m stretch of the track. ST PHOTO: MARK CHEONG

(ST PHOTO: MARK CHEONG)

Efforts are under way to renew the ballast foundations of the North-South and East-West MRT lines (NSEWL), as the ageing stones beneath the tracks show signs of wear after nearly four decades of service.

Ballast, a layer of hard, angular stones, such as granite or basalt, forms the foundation of ballasted tracks.

The stones interlock tightly to hold sleepers and rails in place, keep track geometry stable under fast and frequent train movements and distribute loads evenly across the track bed.

They also absorb shocks and vibrations, reduce wear on rails and wheels and help dampen noise.

Because ballast drains water efficiently and withstands repeated compression, it provides a durable base that is central to safe and reliable train operations.

But after 38 years, the edges of ballast stones on parts of the NSEWL have become rounded and crushed under heavy train loading and exposure to the elements.

The lines, which began operations in 1987, are the only ones in Singapore that operate on a ballasted track.

SMRT demonstrated ballast renewal works during an overnight media visit to Bishan MRT station on the NSL on Dec 11.