AMID THE hustle and bustle of the world’s biggest cities, one thing becomes clear: traffic may be the greatest obstacle in the way of increased productivity. From Moscow to New Delhi to Singapore, governments are initiating large and extensive new metro projects to deal with rising populations and increasing commute times. In Singapore, the 21km section of the Downtown Line Three is underway, using 29 TBMs excavating between 16 station sites in short bores often less than 1km each. By 2017, some 39km of new construction will cut commute times in half in one of the world’s most densely populated locales. The effect of these large projects is equally massive: whole new subway systems built in a single push have a large impact on the local population, are logistically complex, require substantial funding, and can present many challenges to the tunnelling community.
Steve Skelhorn, project sponsor at McNally Construction gives his take on the ongoing trend: "Simply put resources are the limiting factor, people being the hardest one of all. We are currently seeing a knowledge gap between the young graduates now getting into tunnelling and those that are a product of the tunnelling boom in the 1980s and 1990s." Given the world’s worsening traffic, however, getting the right mix of the proper equipment and people is a challenge that many cities are willing to take on.
THE IMPACT OF BIG PROJECTS
Filling the worker gap continues to be the biggest challenge for contractors seeking to qualify their bids: "There has been a lull in work over the last 15 years with many contractors doing one or two contracts simultaneously. Consequently, contractors did not supplement their crew with additional people. With the increase in workload over recent years this has put considerable strain on contractors. Finding skilled people even to pre-qualify is now a challenge," said Skelhorn. The changing face of tunnel projects, such as the use of dozens of machines simultaneously for short tunnels, is also altering the TBM manufacturing and supply chain: "The other logistic problem we have is equipment. For a local tunnel contractor with 90 per cent of work in their back yard, equipment ownership used to make sense and was a major advantage – mobilisation from one project to another was simple.
"With larger and larger projects, and geographically distant ones, the equipment ownership side has diminished. TBMs are now procured for a project as opposed to using an existing machine and making the project match." Skelhorn cited other variables as well, such as the local effects of big international contractors on smaller contractors and the available resources.
Of the biggest challenge, though, he remained certain: "Anybody can buy additional equipment, but not everyone can find the additional right people."
However, international communities of tunnellers are coalescing on large projects in Moscow, India, and Singapore, where they are gaining experience on a grand scale.
MASSIVE METRO: MOSCOW’S MASTER PLAN
In Russia’s capital city of more than 12 million people, the average Muscovite has become accustomed to daily commutes of two hours or more. To ease the perpetually slow flow of traffic, the Moscow Government has initiated a major scheme that consists of at least 50km of new metro line by 2016, and more than doubles that by 2020. At its current pace, Russia’s rate of metro construction will be second only to China.
The metro system, nearly entirely underground, involves the use of dozens of mixed ground EPBMs: the largest simultaneous construction by TBM that has ever taken place in the city. The compact jobsites, complex ground conditions, and tight construction schedules are all challenges that are being met head on, using customised machines, conveyor muck haulage systems, and an army of skilled personnel.
Moscow’s Metro Development Program, unveiled in 2012, calls for 150km of new metro lines within the next eight years. Work thus far has been around the clock, with close to 18,000 workers and specialists engaged in the projects. Their number is expected to reach 35,000 by the end of 2013.
In 2012 alone, 50km worth of new rail were built at 69 different sites. Currently, the effort is largely aimed at preparing the sites where the future stations and lines will be built. This task is a challenge due to the density of Moscow, it is not easy to _ nd appropriate sites that can host train depots, stations, ventilation chambers, emergency exits, and other facilities for the metro. In those areas that have already been designated for metro construction, many utility and communication lines must be relocated.
In a press release issued by the Moscow Government, Marat Khusnullin, deputy mayor for urban development and construction, spoke about the project’s unprecedented scope: "Unfortunately, there is a complication related to the lack of existing construction projects, and therefore the first thing we had to do was to invest in planning and design activities," said Khusnullin. According to the deputy mayor, there has been a shortage in the city of planners and skilled construction workers. Thus, the priorities under the new program are to ease the load at the busiest stations and lines, to revise construction schedules, to build interchange centers and parking lots near metro stations, and to promote underground transit in the city’s outer districts. Plans also call for a third, 42km long interchange circuit that will have a considerable impact on the congestion of some of the metro’s busiest lines.
The entire program will bring the Moscow Metro system to 451km in length and 252 stations at a cost of approximately RUB 100bn (USD 3.2bn) per year. "This country has never built a metro system on this scale, even in the best Soviet years," said Khusnullin.
MIXED GROUND TUNNELLING
Tunnelling is currently underway at dozens of compact jobsites. Most of these jobsites are characterised by Moscow’s challenging mixed ground conditions including fine sand, gravel, loam, stiff clays and boulders. As such, each EPBM must be designed with customised characteristics for the geology. Three new Robbins High Performance EPBMs and one refurbished machine are up to the challenge: The EPBMs, operating at various sites in western and southern areas of the city, are the _ rst in Moscow to use electric variable frequency drives (VFDs). The high thrust and torque capabilities of the machines allow for faster excavation while minimising disturbance that can lead to surface settlement. Active articulation on the machines will enable them to excavate tighter curves without the risk of segment deformation that is present when using passive articulation. Mixed ground cutterheads reinforced with abrasion-resistant wear plate give the option of changing out carbide knife-edge bits with 17- inch disc cutters depending on the conditions.
Two 6.6m diameter Robbins EPBMs are excavating left and right-hand tunnels, each 1.8km in length, for contractor Engeocom. A third, refurbished machine for Engeocom, nicknamed ‘Julia’, is also excavating a 2km section of tunnel. The final machine, a 6.2m diameter Robbins EPBM with mixed ground cutterhead, is boring a 1.9km section of tunnel for contractor USK MOST. All four machines are utilising Robbins continuous conveyors in the mixed ground conditions.
RUSSIA’S RECORD BREAKER
The Robbins machine at USK MOST’s jobsite was launched in winter 2012 from a 15m deep shaft. The machine has been excavating in dense clay and fine sand. "With the homogenous soil conditions, we have been using foam and conditioner to keep the earth balanced and for easier muck removal," said Vadim Bocharov of USK MOST.
By spring 2013, the machine had achieved a record for EPBMs in Moscow, excavating 29.4m in one day, 150m in one week, and up to 500m per month. "The soil condition, crew experience, rigorous schedule, continuous conveyor, and the reliability of the TBM are all factors that helped achieve the record," said Bocharov.
The TBM is scheduled to break through later in spring 2013. After its initial excavation, the machine will be disassembled in the receiving station site and launched on an additional 1.4km tunnel in the first quarter of 2014.
Additional work for USK MOST includes 8km of tunnel and seven stations using multiple TBMs including two Caterpillar and two Herrenknecht EPBMs.
The USK MOST work is just one part of dozens of simultaneous construction operations underway in Moscow.
According to Doug Harding, Robbins vice president of sales, mixed ground TBM excavation in Moscow is the best way to ensure the projects are completed within schedule and on budget: "High Performance type EPBs with properly specified muck haulage systems are the only cost effective solution here, due to the deep nature of the stations and tunnels required for the metro."
A MONSTER UNDERTAKING
New Delhi, India, a city of over 16 million, is also home to some of the world’s busiest traffic. In answer, the Delhi Metro Rail Corporation (DMRC) has built two phases of the Delhi Metro, with a third phase just starting up. Currently the metro is 190km with 142 stations. In the Delhi Metro Extension Phase Three, an additional 140km will be built throughout Delhi and connecting to neighboring cities Haryana, Faridabad, and Bahadurgarh. Some 50km of the new ring lines will be built underground.
"As far as the benefit of Delhi people is concerned, any mass transit system is a benefit to the public. It will decongest many roads, as a large number of people will shift from road to metro. Not only that, but the new line will provide a great support to the working class who commute between Delhi and Faridabad and Bahadurgarh (Haryana), as they can stay in those areas where the standard of living is quite a bit cheaper than Delhi," said Jitender Tyagi, director of projects for the Delhi Metro Rail Corporation.
The underground portion of rail line was proposed for aesthetic reasons and due to the available space in densely populated areas. "Right now four TBMs are currently working but Phase Three has just started. We can expect 26 TBMs will be working simultaneously in and around one year from now," said Tyagi. The ground consists of a mixed face with rock, and DMRC expects that all tunnelling will be done with mixed ground EPBMs.
Phase Three has a tight construction schedule, with completion targeted for the end of 2016. The logistical challenges of launching so many TBMs simultaneously in order to meet the schedule, admits Tyagi, will be many. "Wherever the TBM is launched, we require some space, as land is not available everywhere, so we are waiting for the allotment of land apart from whatever area we have already. The second problem is utility diversion; there are many times water or sewerage lines are present, which need diversion. Monitoring of 26 TBMs at the same time will definitely be a challenge and for that we are planning a centralised monitoring system, which has not yet been finalised but we are planning to have a centralised server and from there management information will be generated. This will smooth construction management."
Also, traffic management around multiple jobsites requires detailed planning for road closures and service lane closures. When near residential areas, the jobsites will also be subject to noise restrictions at night. The new ring lines are projected to carry three million riders annually, and the DMRC is not going to stop there: "Planning for Phase Four has begun. The initial tender should be finalised by 2015," adds Tiyagi.
MORE BIG PROJECTS
The trend of large metro projects will most certainly continue as the world’s populations flock to already crowded urban locations. The DMRC has looked to models in Japan, Singapore, Hong Kong, and Bangkok in researching their design, and hope their system will become a model as well. "Gradually, we have built our own unique metro system.
One improvement will be with ring lines, which encourage connectivity. Our previous reaches of metro were built in long radial lines," said Tyagi. Some of the logistical problems associated with the big projects, says Skelhorn, could be helped with a similar approach to the work in New Delhi. "Mega projects by their nature can last many years and tend to be staffed by very large groups. New tunnellers become part of a very large machine and this can last for the duration of the project. Splitting mega projects into smaller parts actually increases the knowledge base down the road." He cited the Channel Tunnel as a mega project that required many tunnellers all at once and sent them all out into the industry at the same time after the project had been completed, creating an imbalance. Of mega projects, it seems that one thing is for sure: they are on the rise, and will be changing the face of the tunnelling industry for years to come.
