Life in today’s modern urban environment is very much an above and underground experience. As urban populations swelled during the 20th century transport planners found that they could no longer rely solely on a city’s increasingly gridlocked road network. In many cities the green light was consequently given to dig more tunnels that would provide the fast and efficient transport services demanded by an increasingly suburbanized population.
“The idea when developing many of the world’s cities was that habitation should take place on the surface and transport should happen underground,” says Roland Leucker, CEO of Stuva, an independent, non-profit research institution that focuses on underground construction.
“Underground transport, particularly rail which has higher capacity than individual vehicles, is the most effective way to move thousands of people very quickly.”
“While we have seen this in European cities which are home to 1 or 2 million people, it is a particularly pertinent issue now in some of the world’s megacities like São Paulo and Tokyo. These cities each have over 10 million residents which are increasingly spread out. It is essential to have an above ground transport system here, but planners have found that many of the oldest tunnels on some of the world’s most important underground networks were constructed over a century ago and inevitably tunnel engineering has changed significantly since then. Stuva was founded in 1960 at the point when concerns were rising about road congestion in urban centers and tunnel construction was increasingly viewed as the answer to these problems. While tunnel engineering has continued to advance through a steady demand for new transport tunnels, Leucker says that perhaps the most striking technological advance has occurred in the past two decades with the development of tunnel boring machines (TBMs).
“TBMs are built flat faced so that employees can work under atmospheric pressure,” Leucker says. “TBMs are very effective at boring and their use is more conducive to worker safety, particularly as considerations for occupational health standards have increased in recent years in Europe and North America. TBMs have also helped to reduce the amount of time it takes to construct tunnels and decreased costs because you are not so reliant on manual labor.”
ICT advances aid engineering process
In addition to improvements in technologies and techniques associated with fundamental tunnel construction, advances in ICT technology are also aiding the engineering process and improving safety for workers. For example RFID tagging of construction workers and machines is now in widespread use all over the world.
“Every worker should wear an RFID tag in their clothes,” Leucker says. This electronic chip transmits a signal to the control centre so if there is an accident or a problem, controllers can identify exactly where they are and exactly how many people are in a certain area.”
“Communication Technology has also improved the quality and the extent of communications possible in a tunnel environment, both during construction and when the tunnel is operational.”
Another major advance that is aiding safety is the use of sensors to measure settlement displacement as tunnel construction is carried out. These sensors again transmit a wireless signal to the control centre from the continual measurement of ground movement above and below the tunnel structure. Leucker says that displacement of 5-10mm is normal during construction, with the sensor able to detect any dangerous movements immediately, therefore minimizing the chance of damage to structures on the surface which is essential during construction under heavily-developed urban areas.
As well as measuring movement of settlement, sensors are also being used to detect the condition of the tunnel ahead of boring and fitting out. This might include locating old communications and sewage lines that might not have been recorded during previous construction projects thus avoiding any surprises and potential difficulties with relocating this infrastructure.
Leucker says that technology has also improved the quality and the extent of communications possible in a tunnel environment, both during construction and when the tunnel is operational. Previously telephone lines were laid in tunnels during construction to provide links between the various construction sites. Today the availability of advanced wireless technology means every worker can carry a mobile phone, ensuring constant contact with operators above and underground.
Advances in communications technology are also benefiting train operations. Drivers can stay in constant contact with control centers so they are capable of immediately reporting any problems experienced during the journey, improving response times and safety. Passengers can also access this GSM signal on their mobile phones so calls are not dropped when travelling through a tunnel improving journey experience. Onboard Wi-Fi systems are also not impacted when passing through a tunnel.
Making the difference
“Passengers now expect a mobile phone signal when travelling around an urban metro network, or when entering the city on a commuter train. With many long-distance rail journeys taking the same amount of time as a car journey, this could be the difference between a passenger driving and taking the train where they can use their time more productively.”
Leucker says that the success of installing systems with these capabilities means that passengers now expect a mobile phone signal when travelling around an urban metro network, or when entering the city on a commuter train. He says that with many long-distance rail journeys taking the same amount of time as a car journey, this could be the difference between a passenger driving and taking the train where they can use their time more productively.
“Wi-Fi and mobile phone services are not essential for passengers to use an underground railway, but they do improve the quality of journey,” he says. “This gives rail another distinct advantage over the car when travelling long distances.”
By offering high capacity and the capability to move large numbers of people quickly, rail and metro tunnels are improving quality of life and helping the mega metropolises of the 21st century function more effectively. However, tunnel construction is a dirty and noisy process, and can also be very disruptive to the surrounding neighborhoods and environment, particularly in already crowded cities. Leucker therefore says that adopting the right approach to managing these projects is crucial to completing projects on time and on budget.
“People need to be consulted from the very start,” he says. “Stuttgart 21 is an example of where this did not happen and people have since voiced their disapproval quite strongly against a project that I believe will improve transport in Germany. If they were involved in the process and consulted about the plans and the improvements they are going to provide from the very beginning the problems that they have experienced here might have been avoided.”