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The Star - 29th October 2013

New machinery makes headway in MRT construction

BY MENG YEW CHOONG



New machine: For the Pasar Rakyat station, located along Jalan Tun Razak, nearly 300,000 cubic metres of rocks and earth need to be excavated to cater for a total of two tunnels. To speed up excavation works, blasting is supplemented by a surface miner specially brought in for the job.
New machine: For the Pasar Rakyat station, located along Jalan Tun Razak, nearly 300,000 cubic metres of rocks and earth need to be excavated to cater for a total of two tunnels. To speed up excavation works, blasting is supplemented by a surface miner specially brought in for the job.

Construction of the MRT in the Klang Valley is throwing up unusual obstacles that require cutting-edge and customised methods and machinery, some that have not been used anywhere else in the world.

BUILDING a mass rapid transit line in a city that never made proper allocations for rail transit corridors is challenging in many ways, chiefly due to a lack of space to manoeuvre in and to place heavy machinery.

However, the builders of the Sungai Buloh-Kajang (SBK) line of the Klang Valley MRT system are rising to the challenge by introducing machinery and equipment considered new in this part of the world. We look at four innovations used by MMC-Gamuda KVMRT (T) Sdn Bhd, the contractor for the 9.5km underground portion of the line.

Rolling road blocks

ROAD closures, whether partial or otherwise, is not only a source of frustration for motorists but can also be a source of danger for them as well as the road maintenance crew.

Conducting moving works within a fully coned-off area requires long lengths to be prepared in advance, but this is rather impractical if the maintenance work is only for a short while and needs to keep moving ahead several times in a day. Also, the travelling public may not slow down significantly as they may see little evidence of work being done ahead.


Safety feature: With the lorry mounted attenuator, many tasks formerly undertaken after static closures can now be carried out safely and efficiently using what is essentially a mobile road block and signage.

Safety feature: With the lorry-mounted attenuator, many tasks formerly undertaken after static closures can now be carried out safely and efficiently using what is essentially a mobile road block and signage.
Some maintenance contractors employ flagmen, basically personnel who stand in harm’s way trying to inform approaching motorists about impending obstructions by waving bright flags. However, it is a high risk position, indeed.

“They are like human cones,” said Chris Fenton, Head of Safety, Health & Environmental for MMC-Gamuda.

“We did our risk management, and found that the risk from traffic is high – to ourselves and to the public,” said Fenton.

In response to the growing demand from both road users and city councils for a reduction in avoidable static lane closures, as well as to enhance safety for the public as well as its own personnel, MMC-Gamuda has implemented novel – in Malaysia, anyway – mobile traffic management system that comes in the form of a lorry-mounted crash attenuator or crash cushion.

The attenuator, weighing a few hundred kilos, is mounted on the back of a lorry weighing 10 tonnes (eight actually would have sufficed but the company decided to err on the side of caution) so that both the crash cushion and lorry remain stable upon impact.

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The lorry and attenuator in the daytime.
A car hitting the back of a lorry that does have a crash cushion is fatal in many cases for people in the car because of the height of the car seats. The cornerpost of the car (the front pillar is called the A pillar in industry parlance) can deform and collapse into the cabin, even cutting through airbags and killing or seriously injuring the occupants.

Just as important is the safety of the crew working in front of the lorry.

“This device, which is rated to 70kph, is an obvious choice for us,” explained Fenton. “It does look a bit intimidating, and when we deployed this on the road, we found that people are actually slowing down, as well as changing lanes, way back. It is incredibly bright, and can be seen from a mile away. You can say it has improved driver behaviour,” said Fenton, who added that one would have to be really intoxicated to miss it.

While this may seem to be a novelty here, the fact is that this device, costing nearly RM100,000 (excluding the lorry) is mandatory in countries like the United States, Britain, many parts of the European Union, and Australia. Concurrently, the use of flagmen in these countries are either banned or discouraged.

Not surprisingly, highway concessionaires for highways such as Sprint, LDP and Kesas have expressed interest in this equipment. Sprint is especially attracted by the efficiency and practically of this method of lane closure as they have very little space to work with. The Kuala Lumpur City Hall is also very interested, and MMC-Gamuda has demonstrated the capability of the equipment to them already.

In a rather perverse way, “success” will be seen when a car actually hits the attenuator and its occupants are able to walk away from the wreckage. To date, though, no car has crashed into one even though the equipment has been deployed for close to nine months. Not getting any hits, it seems, is another form of success.

According to Goh Chee Young modifying the piling rig to fit under the TNB high tension cables saves time and money.
According to Goh Chee Young, modifying the piling rig to fit under the TNB high tension cables saves time and money.
Modified bored piling machine

CONSTRUCTION of the Maluri station has a rather unique obstacle in the form of overhead high tension electricity cables that form part of TNB’s national grid.

With the cables passing over one corner of the station, MMC-Gamuda did contemplate relocating a few of the 20m-high pylons, but after extensive consultation with TNB, it was decided that the plan was not feasible.

Any shutdown of the grid needs to be planned properly. According to Goh Chee Young, the construction manager for the station, TNB would not allow it under normal circumstances.

“Any shutdown requires at least six months’ notice. It is also very costly to relocate the pylons, which costs around RM4mil each. Land for relocation also needs to be acquired, and the acquisition gazetted first before work can begin.

Altogether, you are looking at nine months for what is one of the most critical stations in the entire line. In this case, time is more crucial than money.”

In the end, MMC-Gamuda arrived at an engineering solution.




Safely low: To make sure the piling rig did not touch the overhead high tension electricity cables carrying 132kV, a customised machine was ordered to fit under the tight clearance.
Safely low: To make sure the piling rig did not touch the overhead high tension electricity cables carrying 132kV, a customised machine was ordered to fit under the tight clearance.
According to Goh, the electricity cables are about 15m from the ground. “TNB requires machinery or equipment working under the cables to have a clearance of at least 5.5m from the lowest point of the cables, which carry at least 132kV.

“This effectively leaves us with a headroom of only 9m. With the math sorted out, it was quickly noted that no machinery exists in Malaysia, or even the world, that enables piling work to be done under 10m.

Normal bored piling rigs are 15.8m tall; so the solution was to get one of the world’s foremost manufacturer of piling rigs, Bauer, to customise a solution for Maluri.

The modified rig is only 7.5m tall when working, making it a contender for the world’s shortest bored piling rig.

MMC-Gamuda ended up paying RM2mil just to modify the rig, which will be going back to Bauer after the task of driving in 85 piles. The drawback is that this machine can only put in one pile per day, with a maximum pile length of 21m, versus two piles daily for a normal mahcine.

The piler has been quietly working for a few months without drawing notice as it is quite a silent worker. So far, none of the residents nearby have complained about noise, says Goh.

This modified piler will have another job waiting for it after Maluri, where it will be sent to Australia, proof that innovations from the MRT construction are also useful elsewhere.

USE SMALL, QUALITY NOT GOOD: According to Dr Ooi Lean Hock calling in specialist contractors with specialised rigs, ancillaries and experience can be considered as moving ahead with the times, as far as Malaysia is concerned.
According to Dr Ooi Lean Hock, calling in specialist contractors with specialised rigs, ancillaries and experience can be considered as moving ahead with the times, as far as Malaysia is concerned.
Specialised ground anchor drilling machine

THE Pasar Seni station is different from the rest as it incorporates part of the old basement from the former Plaza Warisan and UDA Ocean buildings.

The problem of trying to work within a ready-built basement is that the contractor is confronted with very low headroom, generally around 3m, and down to 2m in certain spots.

Challenges come when it is time to put in ground anchors, or struts, to stabilise the wall due to uneven pressure from the earth and ground water behind it.

“It is neither economical nor feasible at this location to design a wall that is infinitely thick to hold the pressure without ground anchors or struts, and in this case, the problem has become more challenging as we cannot use conventional ground anchor drilling machines,” said Dr Ooi Lean Hock, head of geotechnics at MMC-Gamuda.



Compared to conventional ground anchor drills -- which are at least 5m tall (see inset pic) -- this miniature rig from Beretta fits nicely in places with headroom as low as 1.7m.
Compared to conventional ground anchor drills – which are at least 5m tall (see pic below) – this miniature rig from Beretta fits nicely in places with headroom as low as 1.7m.
The solution for low headroom came in the form of three specialised low-profile drilling rigs from Singapore that can fit even in locations as low as 2m, and with ancillaries that can handle variable soil and groundwater conditions in the 2m-high basement.

In some sections of the lower level basement where the soil behind the wall is highly permeable, coupled with the high water pressures at these depths, the soil has to be pre-treated before drilling is carried out.

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According to Ooi, calling in specialist contractors with the specialised rigs, ancillaries and experience in this instance can be considered as moving ahead of the times, as far as Malaysia is concerned.

“In future, we will get more of these situations, when more stations and infrastructure need to be built in highly-built up areas,” said Ooi, who added that using this custom-made solution will make a difference of at least eight-months to the timeline, compared to the best available methodology here.

Surface miner

BLASTING using explosives is the preferred method for removing lots of rocks on account of its relative cheapness. However, when blasting is not practical, or too slow, other methods to excavate a deep shaft in rock have to be deployed.

For the Pasar Rakyat station, located along Jalan Tun Razak in Kuala Lumpur, nearly 300,000cu/m of rock and earth need to be excavated to cater for two tunnels in the future – a volume that is 120 times more than an Olympic-sized pool (which is 2,500cu/m).

This station is the largest on the SBK line, and has the capacity to handle a second line if required (for commuters familiar with the Singapore MRT, Pasar Rakyat will be like either the City Hall or the Raffles Place stations that cater to two lines simultaneously).

According to Ubull Din Om, deputy project manager of construction for MMC-Gamuda KVMRT (T) Sdn Bhd, if they are to rely on blasting alone, the timeline for the excavation would probably have to be extended by at least six months.

“If it is by blasting alone, we probably have to do it three to four times daily. However, it is not easy to schedule blasting in the midst of a highly built-up area. Also, if there is rain or lighting, the blasting has to be cancelled.

According to Ubull Din Om if they are to rely on blasting alone, the timeline for the excavation of the Pasar Rakyat shaft would probably be at least six months longer.
According to Ubull Din Om, if they are to rely on blasting alone, the timeline for the excavation of the Pasar Rakyat shaft would probably be at least six months longer.
“Furthermore, there needs to be a police escort for the explosives to arrive at the site, and traffic jams could mean the explosives might not arrive on time and we could lose a whole day.”

And so MMC-Gamuda engineers visited other countries to see how advanced mining equipment could help in the excavation, and after many rounds of evaluation, they purchased Malaysia’s first surface miner from the United States-based company, Trenco.

The machine, weighing a hefty 150 tonnes, arrived in three containers in April. As it is new to this country, the supplier had to train local operators for two months before they could handle the machine well. The workers are now highly proficient, and can even do maintenance work on the surface miner now.

The surface miner helps MMC-Gamuda achieve its daily target of removing at least 1,000cu/m of rock and earth. The machine scrapes away about 600cu/m daily, depending on the hardness of the rock, while the rest is supplemented by blasting once a day.

Another benefit of the machine is that it churns out spoils with a consistent size of around 10cm, which makes it easy to load onto trucks carrying the spoils away.

Blasting, which produces large boulders, entails secondary blasting or hacking in order to reduce the size so that the spoils can be carried away. Blasting also produces rather rough edges, compared to cutting.

The miner runs up to 12 hours per day, and stops for maintenance, chiefly to change the worn bucket teeth that is made of carbide steel.

Not surprisingly, Ubull described maintenance as being on the high side, as is fuel consumption. “If blasting is feasible, by all means go for it. At any case, this machine, costing us RM9mil (including accessories), has increased our productivity greatly. It is an expensive toy,” Ubull joked.