Rail engineers working with the Gulf environment

13 September 2011

Solving problems unique to the Middle East, such as the impact of sand on rail tracks and humidity on electronic systems, is a priority for the engineers bringing the region’s railway ambitions to fruition

Technical rail challenges in the Middle East

  • Integration of systems, designs and contract packages
  • Sand accumulation
  • Drifting dunes
  • Underground voids
  • Dealing with mountainous terrain
  • High humidity
  • High salinity
  • High water table

Source: MEED

From beginning to end, railways present engineers with a range of challenges. Creating a system where passengers can sit in air-conditioned carriages at a comfortable 21 degrees Celsius, using their devices to work online and moving at 300 kilometres an hour, is complicated.

Sand [can be] so thin it flies with the wind and enters the motors, electronic devices and power systems

Pascale Grasset, Alstom

Some challenges remain the same wherever you are in the world, such as systems and design integration, compatibility with neighbouring railways and other public transport systems, and selecting the most appropriate procurement method. But the arid deserts of the Middle East and North Africa (Mena) add further issues that other regions do not have to face. Those planning rail networks in the Mena region have to consider sand accumulation, camel crossings or high levels of humidity in their designs.

Rail project delivery

Before any of the technical issues can be solved, clients must decide on the most appropriate way of delivering the project and this alone can be a major challenge for both light and heavy rail operators.

“One of the main problems that a new customer has to go through at a very early phase is: ‘How will I buy my metro or tramway?’” says Pascale Grasset, vice president of development strategy and marketing for South Europe, the Middle East and North Africa at France’s Alstom. “‘Do I contract an engineering company to help me buy on a lot-by-lot approach or do I use a turnkey solution?’”

The approach has huge implications for the technical success of the project. A lesson that the region will want to learn from international railways is to ensure the compatibility of the core systems. Ensuring that the signalling system is correctly integrated with the rolling stock and that this is compatible with the telecommunications system, for example, is a key element in project success and can be overlooked.

“The customer needs someone able to define precisely the different systems so that in the end they get on together well,” says Grasset.

For clients, this can mean appointing consultants to act as interface managers or it can mean taking the turnkey approach, as was recently used on metros and tramways in Dubai and Algeria, passing the risk to the contractor, for example, through design and build contracts.

Slab track is more expensive than ballasted … but it enables tunnels to be a little smaller and helps reduce vibration

James Musgrave, Arup East Asia

“We are able to cover the whole electromechanical system, so for the customer there is only one head. We can orchestrate all the different specialities, such as signalling, rolling stock, track works and electrification. Knowing how to define the interfaces and how to sequence the project execution of the different lots … this is the know-how of the turnkey approach,” says Grasset.

Mark Raiss, an international metro expert and special projects director at US consultant URS Scott Wilson, agrees that integration of interfaces is a major issue for new projects, particularly at the design stage. “However you cut it up, there are big interfaces to manage and I am not sure that one is better than the other,” he says, explaining that the regulatory environment can be a big factor in selecting the approach. “The design-and-build model puts more risk and onus on the contractor. It means the client is possibly less in control than he would be if he was controlling the design. But on a project like London’s Crossrail, where you have an awful lot of procedural and approval requirements complying with the Crossrail Act, it would be more difficult to do design and build.”

On Crossrail, where URS Scott Wilson has been a consultant since 2002, the design is being undertaken by the client’s consultant and each has an interface manager as part of the team. Final designs are passed by the client to the contractor, unlike on the Dubai Metro, where the contractor finalised the design.

Regardless of where responsibilities lie, technical challenges such as dealing with sand, humidity and high temperatures must all be mitigated. Experts say that the main issue with sand is its tendency to accumulate on railway lines, particularly on long-distance projects. “Flat areas tend to be sandy and that is an issue of concern for railway operations and maintenance,” says Bashar Rihani, director of Lebanese consultants Dar al-Handasah. “You have to clear the lines more frequently and that requires more staff and equipment and money to spend on maintenance.”

Drifting dunes cause rail delays

In Iraq, which already has 1,900km of track running the length of the country from Rabiya to Basra, drifting sand dunes commonly cause delays to services. A solution employed by Iraqi Republic Railways Company is to use sand removal machines. The local Al-Burhan Group brought a new generation of machines to Iraq in 2008 from US-owned rail equipment supplier Kershaw, which is owned by Caterpillar. The machines act as a plough that delves 10cm below the top of the rail. Side wings push sand outwards up to 4.2 metres and a brush on the back sweeps the sleepers and the fastenings that connect the rail to the sleeper.

Preventing build-up in the first place is preferable, but not always possible. For metros, elevating the sections that run above ground is a common solution. “Generally speaking, the technique is to raise it perhaps 1.5 metres above the surrounding ground. But this creates a 1.5-metre dividing line through the city,” says Raiss.

Another technique is using a slab-track system, rather than ballasted rail lines, as is understood to be the preferred model for Qatar. With slab-track systems, the rails are fixed to continuous concrete slab, rather than sleepers sat on a ballast. The spacings between sleepers can allow sand to accumulate, whereas with slab track it can just blow over the rails. “Slab track is more expensive than ballasted, but it tends to get used on metros as it enables the tunnels to be a little smaller and helps reduce vibration,” says James Musgrave, rail director for Arup East Asia, an engineering consultancy.

Elevating the railway also has major cost implications when considering lines that run for hundreds of kilometres.

Filters needed to improve rail performance

On the systems side, sand can also have a detrimental effect on equipment and appropriate protection is required for trains, depending on their traction systems. “In some Middle East countries, the sand is so thin it flies with the wind and enters the motors, electronic devices and power systems and either breaks the system or reduces performance,” says Grasset. “We use filters to prevent that.”

Sand is also an issue for the telecoms network, as is the high humidity levels in the Middle East. “To have a more efficient communication between train controllers, drivers and the supporting team, you need a reliable communication system that allows the operator to reach the staff on board and allows staff in the field to reach each other using special handsets,” says Rabii Ouadi, head of business development North Africa and Middle East for railway telecoms at Huawei Enterprise, a China-based telecoms provider. “People need to be reachable at any time. This is very important and this system is called GSM-R (GSM railways).”

The GSM-R system uses a base-station sub system (access network), a mechanism that receives and distributes radio signals between the train, the controllers and the supporting team along the route and has a core control network that acts as the brain of the system, receiving and managing the codes transmitted by the access network.

“A base-station sub system (that an antennae is a component of) needs to have strong characteristics. Huawei has experience in placing these systems all over the world in very tough conditions,” says Ouadi. “In the GCC, the temperatures are high, but it is the humidity that the material must be proven against. We have given this a special focus, especially in locations such as the UAE and Qatar, where we are facing 90 per cent humidity. The architecture of base-stations and core networks are designed in such a way that it prevents the inside equipment from being impacted.”

Base-station sub-systems are designed so that the higher the antennae is raised on masts, the greater the coverage of the signal and reduction in exposure to blown sand and extreme heat. “The higher your antennae, the better the wireless coverage and the next antennae can be further away, but, of course, you have to compromise because building a taller mast will incur additional costs through civil construction work and material, so we typically look at heights of 30-50 metres,” says Ouadi.

For metro systems running underground, as is planned for 119km of the new Doha Metro, there are yet more challenges to be tackled. “Building underground is more difficult than building above ground and more expensive, but it has some advantages in that you can avoid services such as roads and utilities,” says Musgrave. However, obstacles below the surface can also cause problems. “In Doha, some of the ground is karstic limestone, which is limestone that has voids in it as a result of water passing through and wearing it away. It creates big holes and you get very strange steep rock cliffs below ground and sometimes they are not well identified,” says Raiss.

If a tunnel boring machine were to fall into a void it could cause serious settlement of the ground above the machine. Raiss points to several solutions, including the use of ground investigation techniques carried out from the inside of the tunnel as the boring machine moves along. Grout can then be pumped into any voids before the machine reaches them.

Rail boom in the Gulf

Beyond these technical problems, the region still has issues of standardisation, and long-term operation and maintenance to consider. Term contracts are likely to be chosen using the equipment suppliers, with requirements to train local operators and engineers.

Although there are still decisions to make and challenges to overcome when it comes to new rail, progress is being made. After many years of planning, contracts are being awarded and, in the case of Dubai and Saudi Arabia, projects are reaching conclusion. The region’s long-promised rail boom is here at last.

Electrification: Oman leads the way

Oman is the only country to have confirmed it will electrify its section of the GCC railway from the outset, with other states choosing to operate diesel-powered locomotives. Qatar is understood to be planning to electrify its links to Bahrain and Saudi Arabia, which will connect to the GCC line.

The electrified sections in Oman will be powered by overhead lines from a land-based power station, rather than running diesel trains that carry their power source on board. As a result, the line will require considerable additional infrastructure. To counter this investment, electrified lines have advantages that can outweigh the extra costs. By being connected to major power sources, electrified lines can have higher output and therefore achieve greater acceleration. Electric motors are also highly efficient.

The consumption efficiency and other benefits have to be weighed against the considerable electrification costs and, in many cases, diesel trains are found to be more cost effective. Frequency of services and their location are key factors in choosing between the two.

“If you operate one train a week, don’t electrify it,” says Pascale Grasset of France’s Alstom. “If you want a line with dense traffic that goes through cities where pollution from diesel engine emissions is an issue, if you want to optimise the global energy consumption and if you measure this after a decade of operation, you will see that the investment of electrifying the network is going to be fruitful.”

Although overhead lines appear simple, their construction involves several challenges, such as the need to carry thousands of amps of current, maintain the same geometry of the route line and ensure they are weather resistant. Maintaining the lines also incurs cost. Despite initially opting for diesel-powered trains, GCC states have the option of electrifying at a later date – should passenger and freight volumes justify the extra investment. This would also enable the use of high-speed trains running at up to 350 kilometres an hour.

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