SINGAPORE - At 43m deep, Bencoolen MRT station on the Downtown Line is the deepest MRT station in Singapore to date.
Commuters have to travel down five escalators from street level just to reach the train platforms. The tunnel linking Bencoolen and Fort Canning MRT stations also runs just 1m above an existing North-East Line tunnel, complicating its construction.
Such engineering feats are increasingly becoming the norm for MRT engineers and contractors, as more and more MRT lines are planned deeper underground to avoid affecting overground buildings.
The Land Transport Authority (LTA) and the Singapore Institute of Technology (SIT) on Monday (Dec 20) signed a memorandum of understanding to establish a Centre for Infrastructure and Tunnel Engineering, focusing on developing underground tunnelling skills that are still lacking among many in the industry.
It is hoped that SIT's expertise in education, research and development, coupled with the LTA's practical experience, will equip more engineers with the specialised skills necessary, as Singapore targets to double the length of its MRT lines to 360km by 2030.
LTA's chief executive Ng Lang said the centre can provide a pool of tunnel engineers to support the agency's ongoing projects, which increasingly includes projects deep below the earth's surface.
"Our rail lines and road projects are going deeper underground to allow for better use of above-ground spaces and to preserve our natural environment. This requires specialised domain knowledge," he said.
SIT president Tan Thiam Soon said the centre aims to be "at the forefront of cutting-edge applied research and training in Singapore, readying future graduates and workforce to meet the challenges of ever-evolving infrastructure and tunnel developments".
Of Singapore's six operational MRT lines now, only the two oldest lines - the North-South and the East-West lines - have stretches above ground.
A stretch of the Cross Island Line still under construction will run 70m under the Central Catchment Nature Reserve, the LTA has said, and new technology has made building deeper a more and more viable option.
Traditionally, the cut-and-cover method - where the ground is opened up, the station built, and then the soil filled back in - has been used. But it is less suited for deeper building, and in recent years, tunnel boring machines have been trialled and become the norm here.
The Thomson-East Coast Line's Orchard station used a retractable micro-tunnel boring machine to tunnel through the ground and install interlocking steel pipes.
A two-tracked tunnel between Aviation Park station and Loyang station on the Cross Island Line will also be built using a large-diameter tunnel boring machine, a first for the country.
Additionally, newer methods are also being used to stabilise soil underground to prevent it from collapsing in during and after construction. The Thomson-East Coast Line Marina Bay station used a ground-freezing process to create ice walls to stabilise the ground before excavation works began.
Mr Wong Keam Tong, a 57-year-old director of engineering, is one of 30 professionals who are enrolled in the pilot course of the centre. The course started in March, and they will be accredited as specialist professional engineers in tunnel engineering in the first quarter of next year.
Mr Wong said many in the industry still lack knowledge of how to excavate deep underground.
"Topics include ground conditions which affect tunnelling works, how to find the best alignment for underground tunnels and how to maintain public safety during tunnelling works," he said.
"It is a factory under the ground, and we need to know how to put in chemicals to either soften the ground or if it is too sandy, make it more lumpy. We don't want any case of a collapse."