Building Challenges

The construction of the Circle Line was a feat that required innovation in design, engineering and construction. Imagine tunnelling under densely packed Singapore, just below the surface of existing roads, busy expressways, buildings and a maze of underground structures!

Soft Soil Conditions

Engineers faced soft soil conditions at the Millenia and Nicoll Highway stations. They also had to be cautious when boring tunnels under the Kallang Basin. Various construction methods were used to combat these conditions:

Interlaced Tunnels & Cables

Circle Line tunnels would sometimes be build close to the Kallang-Paya Lebar Expressway (KPE) tunnel, the Deep Tunnel Sewerage System and PowerGrid’s cable near the Upper Paya Lebar/Airport Road junction. Our engineers had to exercise extreme precision to avoid collapsing train tunnels.

Sticks & Stones

One of the many challenges was having to extract 500 reinforced concrete and steel foundation structures called piles. At Mountbatten station, we encountered rock at fairly high levels and had to use explosives to break the rock up before we could proceed further.

Nicoll Highway Collapse

A section of the tunnel collapsed when a retaining wall gave way, leaving a collapse zone 150m wide, 100m long and 30m deep. As a result of this accident, the first phase of Circle Line was completed in 2010 instead of 2008, and stricter safety regulations were introduced for future MRT projects.