LTA: North-South Corridor Singapore engineers face most challenging construction phase as rocks and viaduct slow work progress

Summary

• Construction of Singapore’s North-South Corridor has entered its most technically demanding phase, with difficult ground conditions slowing some works.

• The 20km project includes an 8.8km elevated viaduct and 12.3km tunnel section, with construction underway since 2018.

• At Novena, tunnelling passes within about 1m of the North-South Line, requiring slower excavation and extra ground support measures.

SINGAPORE: The North-South Corridor (NSC) is moving into its toughest construction stage, with engineers facing hard rock, groundwater and tight working spaces.

The Land Transport Authority (LTA) said the challenges have required changes to construction methods and extra ground stabilisation.

LTA second deputy group director for the NSC project Ang Pui Boon said ground conditions became harder in some areas as work progressed. Teams have had to adjust their plans to protect workers and nearby infrastructure.

The NSC will stretch more than 20km from Singapore’s northern towns towards the city. It includes an 8.8km elevated viaduct and a 12.3km underground tunnel section.

The viaduct is expected to open from 2027, with the full project opening in phases, Channel NewsAsia (CNA) reported (Sept 12).

Building Singapore’s longest viaduct

The 8.8km viaduct will be Singapore’s longest. It is about 40m wide and 19m tall, requiring more than 6,000 precast pieces.

Much of the installation happens at night, during four- to five-hour windows. Crews must work around live roads, major junctions and existing transport infrastructure.

Some foundation work at Gambas Avenue and Woodlands Avenue 8 has taken longer because of utilities and ground conditions.

More than 90 per cent of foundation work is now complete. Attention has shifted towards columns, crossheads and launching viaduct sections over roads and MRT tracks.

Tunnelling only metres from MRT lines

Novena presents an especially difficult challenge. One NSC tunnel section passes within about 1m of the North-South Line.

Workers encountered fractured rock and groundwater while excavating beneath the existing MRT tunnels.

LTA has switched to smaller excavation sections, supported one at a time. Extra rock removal, grouting and monitoring are also being used.

Similar work is taking place at Nicoll Highway, where the NSC passes above Circle Line tunnels with only 1.5-2.5m of clearance.

In Thomson, hard rock and large boulders have required controlled blasting and changes to earth-retaining systems.

The disruption should eventually ease

Residents and businesses have had to live with hoardings, noise and restricted access during years of construction.

LTA said noise should taper as heavy foundation works wind down. More upcoming work will happen underground, reducing noise and traffic diversions.

Businesses in areas such as Novena may still face reduced visibility and footfall. LTA said it will continue working with affected owners on measures such as signs and advertising banners.

For a project this large, patience is part of the price. The sensible goal is to finish the road safely, without rushing the parts that sit centimetres from Singapore’s existing transport network.