If you think creating the MRT train tunnels that Singaporeans travel in every day is as simple as digging a hole and laying tracks, that is far from the case, says Land Transport Authority (LTA) deputy director Alvin Sim. The engineer, who has been with LTA for 14 years, has worked on the tunnels for the Downtown and Thomson-East Coast lines, and is currently working on the Cross Island Line.
As Singapore speeds towards its goal of expanding its rail network to about 360km by 2030, it is tapping some of the world’s most sophisticated machinery to keep the building process humming along.
Specialists like Mr Sim oversee the construction of tunnels to ensure they are safe and of high quality, while keeping construction projects on schedule and within budget.
Learn how Singapore builds the underground tunnel network that connects the city.
For the 39-year-old, helming daily meetings for such massive tunnelling projects to make sure they remain on track is par for the course. He sleeps with his phone within reach at night so he can immediately respond to unforeseen issues – such as groundwater ingress – and ensure that the tunnels are well constructed to enhance the nation’s connectivity.
“Like other developed cities with limited space, the more we harness our underground space, the more precious land area we free up for uses such as housing and recreation in land-scarce Singapore. This is why we must continue to develop and be strong in our underground engineering capabilities,” Mr Sim explains.
Tunnel boring machines (TBMs) are used to excavate Singapore’s underground space to create tunnels. Like giant mechanical earthworms, the TBMs eat away at rock, soil and other materials in the ground to create the tunnels.
Mr Sim, who started working on tunnelling projects fresh out of university, has had a front-row seat to how the LTA and Singapore’s built environment industry have embraced construction innovations. This includes the use of Building Information Modelling (BIM) to aid design, planning and coordination of construction works.
He says: “BIM has been a game changer. In the past, reliance on 2D plans meant that our designers had to make numerous revisions to the drawings whenever tunnel alignments were modified. This was laborious, time-consuming and occasionally subject to human error. Moreover, engineers had to study multiple 2D drawings to grasp the spatial complexities of our projects.”
BIM helps collate the 2D drawings and transform them into 3D models for easier understanding. Mr Sim adds: “This also helps us better identify potential clashes and conflicts at the early stages of design, and helps us make informed decisions so we can keep our projects safer.”
With revisions to 3D BIM models documented on a shared platform, multidisciplinary teams can review and optimise designs at the same time, increasing workplace productivity.
With the built environment sector moving towards digitalisation to increase productivity, more companies are adopting digital tools like Building Information Modelling (BIM) to streamline their operations.
Innovating for better productivity and efficiency requires investment but firms can seek help to defray this cost. Companies in Singapore can tap the Productivity Innovation Project (PIP) incentive scheme to have up to 70 per cent of costs related to tech adoption and innovation co-funded.
The PIP offers financial support in three areas: technologies and innovations, design for manufacturing and assembly, and integrated digital delivery. Companies that adopt innovative solutions under any of these areas can submit their proposal by Dec 31, 2024, to qualify for co-funding. Co-funding will be provided based on the potential for productivity improvement on site.
Learn how the Productivity Innovation Project can help you and your business.
With each project, built environment professionals in Singapore devise solutions to problems and hone approaches to excavation and construction.
An example is LTA’s recent work on the Circle Line. When finished in 2026 with three new stations – Keppel, Cantonment and Prince Edward Road – and their tunnels connecting the HarbourFront and Marina Bay stations, the line will reduce commuters’ travelling time. Currently, it takes about 30 minutes to get from Telok Blangah station to Marina Bay station. It will take 20 minutes once this section of the line is completed.
The area surrounding the works for the new stations and tunnels includes national monument Tanjong Pagar Railway Station, commercial buildings in the Central Business District and key road infrastructure such as the Keppel Viaduct. To maintain the integrity and stability of these important structures, the project team had to be innovative in carrying out the tunnelling process.
To construct the tunnel between the Keppel and Cantonment stations, the team bored through part of the foundation of the Keppel Viaduct, specifically some of its reinforced concrete piles.
Says LTA senior project engineer Bryan Chng: “We needed to cut the metal rebars into manageable chunks, or they could have gotten entangled in the TBM and hindered it from maintaining the required face pressure. That could have led to ground settlement on the surface.” Rebars are steel bars used to reinforce concrete piles.
Mr Chng, who shares that he is in his 20s, is in charge of reviewing the Circle Line project’s construction design and maintaining its works’ safety and quality.
For the first time in Singapore, the project team deployed specialised tungsten carbide-reinforced cutter tools on the TBM, designed specifically for cutting through such reinforced concrete piles. “Using these specialised tools on the TBM, productivity and safety were improved as workers didn’t have to enter the front of the TBM to manually hack the piles,” says Mr Chng.
To protect the viaduct’s structural integrity and its users’ safety, an extensive range of monitoring instruments was deployed to monitor it during the underpinning and tunnelling works. These included digital levels to monitor ground movement, as well as tiltmeters to measure the inclination of vertical structures aboveground (see Ensuring safety above ground while tunnelling).
For the tunnels between the Cantonment and Prince Edward Road stations that pass under Tanjong Pagar Railway Station, the project team had to play detective.
Because the original drawings, which were hand-drawn on paper, had faded over time, little information on the foundational structures was available. The engineers had to be creative – they used seismic waves to determine how deep the foundation was and whether it clashes with the tunnels’ planned alignment.
Measures like these ensure that tunnelling works do not affect existing structures above and near them.
When boring under or near structures, extensive foundation investigation works are usually carried out before tunnelling starts, to check that their piles are not within the tunnel’s alignment.
Before the project team tunnelled under Tanjong Pagar Railway Station, it applied extensive instrumentation techniques, including the use of sensors, to keep an eye on the building’s structure, and detect any minute movement during the tunnelling.
Mr Cheng Ch’ng Yih, a qualified person (QP) from Ronnie and Koh Consultants whose job is to ensure that builders follow design blueprints and safety standards on site, supervised work on the Prince Edward Road Station and its tunnels. The 47-year-old says: “We check these sensors’ readings every four hours, and receive alerts if these exceed certain threshold levels. Appropriate actions, such as adjusting the TBM’s operating parameters when needed, can then be implemented in a timely manner.
“For the Circle Line tunnel boring works, we tracked the amount of excavated material every day. There is a chance that we may excavate more than we should, resulting in issues like ground movement which could affect the stability of infrastructures within its vicinity. That’s why we need to reconcile what we are taking out.”
To Mr Cheng, his work helps to maintain safety for the public and the people building Singapore’s infrastructure. “We all have a role to play in ensuring safety during construction, from the builder to the client to my team. At the end of the day, we have a duty of care to one another to make sure that we go home safely to our loved ones.”
Mr Sim adds: “My career in the built environment sector has been very rewarding. I have been exposed to roles in both operations and policy, and this has given me an appreciation of the exciting engineering that we are doing across the public service. Knowing that our work contributes to enhancing connectivity across our island gives me all the motivation that I need to do my job well.”
For those looking at a career in built environment or hoping to upgrade their qualifications in construction and engineering, there are certifications and courses available:
Diploma:
Industry practitioners:
Building Singapore is a five-part series featuring the people behind the nation's built environment sector who are transforming the urban landscape. Get an inside look at how they are creating more liveable, sustainable and vibrant spaces for Singaporeans to live, work and play in. This feature is the second in the series.
Find out more about the Built Environment sector here.