The revival of the giant tunnel boring machines

  • Living
  • Tuesday, 27 Feb 2018

S776 underwent a Factory Acceptance Test in the TBM Refurbishment Plant in Pusing, and is now ready for action.

In less than 48 hours from now, Prime Minister Datuk Seri Najib Tun Razak will press a button to bring to life a machine that has been lying dormant after its mission to Kuala Lumpur was completed four years ago.

That machine is codenamed S776, a state-of-the-art variable density tunnel boring machine that had proved its prowess by playing its part in excavating the 9.5km long twin tunnels of the Sungai Buloh-Kajang MRT Line, which is now serving nearly 120,000 commuters each day.

S776 may look spanking new to the untrained eye, but it is actually a refurbished machine (more on this later).

S776 was retrieved from the ground in 2014, after fulfilling its role along with another nine tunnel boring machines (TBMs) that worked simultaneously at other parts of the underground alignment that now hosts seven stations: Muzium Negara, Pasar Seni, Merdeka, Bukit Bintang, Tun Razak Exchange, Cochrane, and Maluri).

S776 was fabricated by Germany-based Herrenknecht, which has a manufacturing factory in China. This TBM, along with others ordered from Herrenknecht, were shipped piece by piece to Malaysia in 2012 before being assembled on site.

The journey of S776, with an external diameter of nearly 7m, weighing in at approximately 1,100 tonnes, and up to 140m in Iength when operational, is testament of how far Malaysia has progressed in terms of underground construction competency, specifically on mechanised or bored tunnelling.

“When S776 was pulled out of the ground in 2014 after just travelling a kilometre or two underground, great care was taken to protect this expensive investment – each variable density TBM costs up to RM50mil each, from the elements so that they can be preserved in good condition for the next job,” said Gamuda Engineering managing director Datuk Ubull Din Om.

tunnel boring machines
The locally trained tunnel crew is now well-versed in the mechanised TBM operation.

A TBM can actually live on for a very, very long time as each and every component (save perhaps for the TBM shield) is replaceable or repairable, very much like how a car can be kept going after undergoing an overhaul.

He added that with a careful maintenance regime, used TBMs still have lots of mileage left in them, and in view of this, there is actually a thriving market for used TBMs all over the world.

“In fact, two of the machines that worked on the Sungai Buloh-Kajang Line were exported to India, where they are still working to expand India’s metro network,” he said.

tunnel boring machines
Datuk Ubull Din Om, managing director of Gamuda Engineering Sdn Bhd.

Completion of Sungai Buloh-Kajang MRT opens new doors

At the end of the tunneling programme for the Sungai Buloh-Kajang Line, the underground work contractor, MMC-Gamuda KVMRT (T) Sdn Bhd (or MGKT), inherited a sizable pool of trained personnel who are now highly conversant with underground construction work, which imposes different demands on timeline, machinery, and complexity compared to building structures on ground level, or above it, such as the elevated portions of the MRT.

Any delays in underground work could be difficult to remedy as the space is tight, and there is not much room to easily scale things up such as adding machinery like other kinds of construction work.

Ubull admitted that MGKT’s competency in terms of managing its assets will be put to a gruelling test this year as both men and machinery will be worked to the hilt to excavate the 13.5km pair of twin tunnels – the longest ever rail tunnel in Malaysia that passes through at least seven (known or inferred) treacherous geological fault zones, each of them capable of throwing a spanner in the smooth journey of any tunnelling programme, no matter how experienced the contractor is.

The journey of S776

This tunnel boring machine (TBM) was assembled at the Cochrane launch shaft when it arrived in pieces from China in 2012. After finishing her job for the SBK line, she was mothballed at a custom-made TBM refurbishment facility at Pusing, near Ipoh.

The team that worked with this machine from the start were also sent to Pusing so that they could disassemble the TBM so that critical components could be replaced, while others parts were repaired. Extra care was made to ensure the main bearings – arguably one of the most critical parts of a TBM – remained in good condition as bearing failure with the TBM stuck tens of metres underground will make any tunnel engineer cry, especially if there is no available space to dig a “rescue shaft” to reach the machine from the ground surface.

Caring for all these mechanical components mean frequently turning them so that they don’t get “stuck” in a fixed position for long, other than oiling them every now and then. Stripping each TBM down also allowed technicians to fully understand in greater detail how things work, and the final test for them is that they have to assemble the TBMs, and restart them at the factory so that external auditors can certify that the machines are fit to run.

Sungai Buloh-Serdang-Putrajaya (SSP) tunnel drives, tunnel boring machines

With tender, loving care, S776 is now reassembled at the Bandar Malaysia North launch shaft, which will eventually form part of the Bandar Malaysia North MRT station.

The Sungai Buloh-Serdang-Putrajaya or SSP Line will have 12 TBMs, eight of them refurbished in Malaysia at the Pusing-based facility which is the only one of its kind in the region.

“The refurbishment plant set up is a strategic move by MMC-Gamuda leading up to cost and time savings for the Government,” said Salehudin Md Shaarani, tunnelling manager with MGKT who started off his tunnelling career by working at the KTM Ipoh to Padang Besar double-tracking project (featuring two tunnels).

The cost savings are significant given the steep price of these sophisticated TBMs. In this regard, MRT project owner Mass Rapid Transit Corporation Sdn Bhd is also to be commended for its clear thinking in allowing refurbished TBMs to be used in the SSP Line. Not all project owners think alike, with some, such as Singapore’s Land Transport Authority, insisting on brand-new machines to be used for each tunnelling drive, no matter how short it is.

Even as the TBMs are being renewed, Malaysians are getting upskilled in ways they could not have imagined. Salehudin himself is a sterling example of the upskilling of locals who grew from knowing nothing about tunnelling to become someone so highly involved in managing tunnelling worksites.

Other than engineers like him, hundreds of technicians have now acquired the skills to work in any worksite in the world. Some did venture overseas to work in other tunnelling jobs, some stayed behind after being reassigned to other tasks, while the truly outstanding ones were “persuaded” by MGKT to return home to rejoin the team.

Another crucial piece of the puzzle in the creation of a tunnelling workforce is MMC-Gamuda’s Tunnelling Training Academy (TTA) at Shah Alam, which is considered another rarity in this region. Like a finishing school for underground construction workers, more than 1,000 Malaysians have already passed through its door. In fact, Salehuddin is a product of the TTA when he joined Gamuda as a young engineer.

ssp line tunnel boring machines
Salehudin Md Shaarani explaining about the SSP Line underground stations and the geological formation complexities.

After continuous exposure to underground work, he is now competent enough to pass on his knowledge to younger engineers and technicians. “Working underground is unlike other regular construction work. It is exciting in the sense that each new day may throw a new challenge at you. You will be stretched in ways you never imagined, but you end up wiser and more knowledgeable. Tunnelling cannot be learnt in classrooms or universities. It is a live subject that can only be learnt by people who are hungry and eager to learn,” he said.

The preparation of the tunnel launch shaft is a feat in itself, as Bandar Malaysia North station lies in an area filled with cavities, courtesy of weathered limestone in a geological formation known as karst. And Kuala Lumpur’s karst is the absolute worst kind for underground work as it is the most weathered grade of limestone.

To prepare the shaft, 190 of the 472 bored piles have been sunk in at the perimeter to create a stable and watertight rectangular box so that men and machinery can work safely. The shaft measures 128m wide, 28m long, and 20m deep, and within this tight space, pieces of the TBM had to be slowly lowered by gigantic cranes in order to be assembled before it starts boring.

While casual observers will just see Prime Minister Datuk Seri Najib Tun Razak pressing the button, engineering enthusiasts are cheering the restarting of S776 as it marks another important milestone in Malaysia’s journey towards the acquisition of deep knowledge about tunnelling.

S776 launch will be followed by another 14 launches over this year. Under the current work schedule, it will disappear underground until the last quarter of 2019. After tasting the convenience of rail, commuters who are wishing that Malaysia will speed up its MRT network expansion are surely hoping that S776 will not have to spend another four years in a workshop waiting for its next job.

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