Ground conditions delay Singapore North

Singapore’s Land Transport Authority (LTA) has pushed back completion of the 12.3km tunnelled section of the North-South Corridor (NSC) by around two years after encountering difficult rock and groundwater conditions along several sections of the route. The tunnel section, running from Lentor Avenue to East Coast Parkway (ECP), is now expected to open in phases from 2031, compared with the previous target of 2029. LTA said more than 90% of foundation works for the tunnels have been completed, with major excavation continuing along the alignment. Among the most technically challenging works are at Novena, where the NSC passes both above and below the operational North-South Line (NSL) MRT tunnels, with clearances reducing to around 1m. Fractured rock and groundwater inflows beneath the live NSL forced contractors to adopt a more controlled and time-consuming mining approach than originally planned. Excavation is being undertaken in smaller sections, involving repeated cycles of rock removal, grouting and installation of ground support. LTA said the methodology was necessary to control ground movement and settlement and protect both MRT operations and surface traffic. Construction requires careful sequencing and continuous monitoring because of the extremely constrained interface with the existing tunnels. Further difficulties have been encountered at Thomson, where investigations identified harder-than-anticipated rock and highly variable ground conditions. Extensive controlled blasting, additional rock excavation and ground stabilisation have been required before excavation could proceed. Construction methodologies and earth-retaining systems have also been modified to accommodate the conditions and maintain excavation stability. The challenges at Novena and Thomson, together with difficulties affecting the NSC’s viaduct works farther north, have cumulatively added approximately two years to the programme. The 8.8km viaduct between Admiralty Road West and Lentor Avenue will consequently open in phases from 2029 rather than 2027. LTA said it would continue to deploy additional manpower and equipment and optimise construction sequencing where possible. More construction activity is expected to move underground from 2027, allowing roads and footpaths occupied by the works to begin being progressively reinstated from 2028. The 21.5km NSC comprises 12.3km of tunnels and 8.8km of viaduct and will connect Singapore’s northern districts with the city centre. The corridor will link with the Seletar, Pan-Island and East Coast Parkway expressways and is intended to relieve congestion on the Central Expressway and surrounding arterial roads. Comments: