Singapore – As part of works to construct railway tunnels at the Thomson-East Coast Line (TEL) Marina Bay Station, the Land Transport Authority (LTA) has successfully carried out a ground-freezing process to create ice-walls to stabilise the ground.
This is the first time such a technology is being used by LTA to improve ground conditions before railway tunnel excavation works begin. The formation of ice walls will help to prevent water seepage during mining works, as the soil comprises mainly of permeable Old Alluvium. The ground-freezing will also help ensure that works have no impact to the safe operations of the Circle Line and North-South Line tunnels located above the TEL tunnels.
The Ground-Freezing Process
The ground-freezing method adopted for TEL Marina Bay Station was done by installing a series of freeze pipes into the ground. Chilled brine at a temperature of -30 degrees Celsius is circulated within the freeze pipes, to allow the surrounding soil to freeze and form individual ice columns. The columns will then grow in size and join together with neighbouring columns to form one continuous, impermeable ice wall.
The ground-freezing process at TEL Marina Bay Station worksite started in March 2018. After about two months, two ice walls 1.8m in diameter were formed about 40 metres below ground level. The ice walls will be in place for about three months until the construction of the TEL’s Woodlands-bound tunnel is completed. The freeze pipes will then be deactivated, allowing the ground to thaw. Following which, construction works for the upper Changi-bound TEL tunnels above it will commence.
The contract to construct TEL Marina Bay Station and its tunnels was awarded in February 2014, and is expected to complete in 2021.
The Progress of TEL
The 43km-long Thomson-East Coast Line (TEL) will add 31 new stations to the existing rail network, with seven interchange stations linking the TEL to all five existing MRT lines. Besides enhancing connectivity between the north, central and eastern parts of Singapore, the TEL will strengthen the resilience of the rail network by providing alternative travel routes for commuters on other lines.
The construction of TEL is progressing well, and commuters can start enjoying the TEL in stages from 2019. When fully operational in 2024, the TEL will be Singapore’s sixth MRT line, and is expected to serve approximately 500,000 commuters daily in the initial years, with the figure rising to about one million commuters in the longer term.
- 2019: Woodlands North – Woodlands – Woodlands South
Structural works for the stations and tunnels are mostly completed. Track laying, architectural and Electrical and Mechanical (E&M) fitting out works are about 12% complete. Depot architectural and E&M fitting out works are 25% complete with tracks in the depot substantially completed. The depot received its first TEL train in May 2018.
- 2020: Springleaf – Lentor – Mayflower – Bright Hill – Upper Thomson – Caldecott
Structural works for all six stations, as well as the tunnels connecting them are nearing completion. Track laying, architectural and E&M fitting out works have commenced.
- 2021: Mount Pleasant – Stevens – Napier – Orchard Boulevard – Orchard – Great World – Havelock – Outram Park – Maxwell – Shenton Way – Marina Bay – Marina South – Gardens by the Bay
The excavation and structural work for stations are about 60% complete whereas around 75% of tunnel drives are complete.
- 2023 -– 2024: Tanjong Rhu – Katong Park – Tanjong Katong – Marine Parade – Marine Terrace – Siglap – Bayshore – Bedok South – Sungei Bedok
Foundation and excavation works for the stations are in progress in tandem with road and services diversions. Tunnelling works have commenced and are making good progress.
The installation of retaining walls for construction of the East Coast Integrated Depot are substantially completed. The excavation and structural works are about 15% complete.