The 2019 World Tunnel Congress (WTC) and 45th International Tunnelling Association (ITA) General Assembly took place in Naples in May. The show featured the usual programme of technical sessions on the use of underground space, but this year saw some unusual underground space topics being broached: floating tunnels, underground farming and even tunnelling equipment requirements for the moon.
The theme for this year was ‘Tunnels and Underground Cities: Engineering and Innovation meet Archaeology, Architecture and Art’. The theme was first introduced by Italian tunnelling society (SIG) chair Andrea Pigorini as he presented a new book The Italian Art of Tunnelling 2019, which covers the nation’s tunnelling heritage.
“All roads lead to Rome”, as the book states, and tunnelling in Italy dates back to the time of Ancient Rome, where they began tunnelling to overcome challenges posed by Italy’s topography.
Pigorini says, “This Rome-centric view of the medieval world emphasised the road network’s role as a driver of commerce and power. They built upon the sophisticated road system of the Roman Empire, which was constructed to connect provinces and colonies within Europe across mountains and ridges.”
Modern engineering practice in road and tunnel design has expanded the network and converted this heritage into modern physical infrastructure assets, developing underground solutions to overcome topography barriers and urban constrains.
Due to its topography, Italy is the European country with the highest number of rail tunnels (according to SIG). The operating network has a length of approximately 16,777km and the total length in tunnels is about 1,524km, representing 9% of the entire network.
US Tariffs are shifting - will you react or anticipate?
Don’t let policy changes catch you off guard. Stay proactive with real-time data and expert analysis.
By GlobalDataItaly’s tunnel network is the second longest in the world after China, which boasts more than 2,100km, and it leads the European ranking followed by Norway, Switzerland, Austria and France. It now needs to be connected to the Trans-European Transport Network (Ten-T) as much as possible, through projects such as the Brenner Base Tunnel.
Pigorini adds, “What we understood at WTC 2019 is that infrastructure needs to be placed in underground spaces to respect environment and history. Infrastructure also needs to be not only robust and functional, but also beautiful, and that is possible thanks to a combination of engineering, archaeology, architecture and art.”
Looking forward
Pietro Salini, chief executive of Salini Impregilo, changed the conversation to the future. He emphasised the need to build long-lasting, sustainable infrastructure that will last up to 100 years from now. Although it was not mentioned explicitly, the connection to the Genoa bridge collapse that killed 43 people in 2018 is clear to the Italian industry.
“Tunnelling is a sector which is evolving throughout the world, and planning is required to face the challenges posed by major trends such as population growth, resource scarcity and urban growth. To face these trends we need to develop the skills to manage and gather a vast amount of data,” he adds.
Salini mentioned the development of automation in the construction process to improve performance and reduce costs.
“Sustainability will become more and more of a driver to lead the development of the sector, especially in cities that are pursuing sustainable development through major infrastructure. Two-thirds of the world’s population is set to live in urban areas by 2030,” Salini says. “Building infrastructure is not only a combination of technical skill and technology, but also a craft in the development of humanity to create well-being and employment everywhere. Investing in the future means investing in our youth, committing ourselves to offer new opportunities to those who want to work in our sector.”
The tools
Martin Herrenknecht delivered the annual Muir Wood Lecture, going through the history and evolution of mechanised excavation.
“We construct underground infrastructure all over the world in almost every ground condition,” he said. “Innovation allows us to carry out projects that until even a few years ago were impossible.
He added: “Now [even] Norway is using a double shield technology, and we are looking at increasing shield diameters up to 20m. The reason is to build bigger tunnels with a double deck structure to offer multi-purpose services.
“The future is moving towards multi-service vehicles, digitalisation and sensors in tunnelling as well as mobile phone access to adapted sensor boards to control the jobsite and check the work in progress.”
Outside the box thinking
New technologies
During the conference an open session was dedicated to the theme “Tunnels: a resilient link between past and future”, focusing on repair and maintenance prediction. Speakers illustrated a variety of tunnel projects that explored the use of artificial intelligence (AI), the Internet of things (IoT), big data and BIM methods in implementing efficient analysis of aging infrastructures and repair needs.
Other topics included “Tunnel life-cycle considerations. How long-term maintenance requirements are addressed during design, construction, and asset financing”, and another dealt with “Surveying and maintenance work”, in particular maintenance strategies, which need to be based primarily on proper and appropriate survey and monitoring of the asset.
The discussion also focused on asset inspections when performed at intervals that can vary significantly depending on the asset and the country. Monitoring methods of the past were limited to visual inspection and manual measurements, whereas today, BIM methods make for greater efficiency.
Other methods, however, are also being used like nondestructive scanning and thermography, and destructive methods such as coring. New technologies are being developed using IoT, AI and data analytics for example. When repairs are required, the challenge is being able to make such repairs under live conditions or during minimal outage periods.
Floating tunnels
Floating tunnels were another emerging topic at this year’s WTC.
To limit the environmental impact caused by construction projects, immersed tunnels can create underground connections that can be environmentally favourable compared to surface structures.
Major projects are being undertaken worldwide, but Norway seems to have taken the lead with numerous initiatives, such as the world’s first submerged floating tunnel, which will cross eight fjords, including three of the largest in Norway: Sulafjord, Sognefjord and Bjornafjorden. This project is part of the 40bn EUR construction of the European Route E39, designed to eliminate ferry crossings and speed up traffic on the drive from northern to southern Norway along its western coastline, a drive that currently takes 30 hours to complete.
In Norway the Rogfast tunnel project is ongoing and when completed, the tunnel will be the longest underwater road tunnel (27km) and the deepest (-390m).
To the moon
From the underground up to the moon – this is the challenge posed by Jamal Rostami of the Colorado School of Mines. Rostami illustrated the school’s project: Lunar equipment and techniques for tunnel boring on the moon.
“Space is becoming a passion for a lot of people again,” he said. “There are discussions about going back to the moon, this time to stay. But that implies that once up there, humans need to be shielded from radiation and freezing temperatures in structures which maintain atmospheric pressure in a vacuum.
“Our idea is to actually start underground, using TBMs to make a continuous opening to create habitats or connect the colonies together.
“Technically, weight is an issue, as it’s expensive to take a kilogram of material from the earth to the moon. Our machines weigh hundreds of tonnes, so it’s not feasible to take the machines as they are. We have to convert the design into one where all the components are optimised.”
Borboun excursion
A trip through history was given by via a tour of the famous Bourbon Tunnel. The tunnel and surrounding underground environment demonstrate the last 500 years of Naples’s history.
In 1853 Ferdinand II of Bourbon signed a decree to design an underground viaduct as a military passage in defence of the royal palace for the troops and as an escape route for royals. The tunnel connected the royal palace to a square close to the sea, and to the barracks.
The architect Errico Alvino designed an excavation with trapezoidal section, width and height of 12m, divided into two finished tubes for travel in opposing directions. These finished tunnels had to be large, 4m each, and separated by a slim parapet supporting the gas lamps, and with lateral 2m wide sidewalks.
In 1853 Alvino began the excavation from a former quarry where the current access to the gallery is located, this was the only direction of excavation.
After approximately 245m of excavation, two large tanks from the 17th-century water network were encountered. To avoid depriving residents of water, Alvino designed an 8m-high walkable bridge from the bottom of the tanks as well as rising colossal walls in tuff and bricks to isolate themselves from possible access due to the presence of any further wells.
Two vertical shafts were dug in the streets of Santa Maria Egiziaca and Monte di Dio to ventilate the tunnel. Later, in order to prevent the access of strangers, and potentially endangering the soldiers passing through the tunnel, Alvino decided to build an arched wall under a ventilation shaft to close it. For the other ventilation shaft, Alvino wanted to excavate a recess into the tuff to house the wall and the arch, but the whole operation was never completed so this shaft is still visible.
Tunnel works were completed in May 1855 after about three years of work. Excavation was entirely done by hand with picks, hammers and wedges, and with the aid of lighting provided by torches and candles. On 25 May 1855, the Bourbon Tunnel was decorated and illuminated for the visit of Ferdinand II of Bourbon, remaining open for public transit for only three days.
During the Second World War, between 1939 and 1945, the tunnel and some former neighbouring cisterns were used as shelter for citizens. Between 5,000 and 10,000 Neapolitans, who lost their homes during bombings, took shelter down there and lived for some years. Their daily routine was moved underground; even a baby was born in the tunnel. After the war and until 1970, the Bourbon Gallery was used as a police vehicle impound.
In 2007 geologists Gianluca Minin and Enzo De Luzio were working in the tunnel when they discovered a walled passage that separated it from another large cavity that had been turned into an air-raid shelter. Here the same geologists found another access route to the shelter, which in the 17th century was already an entrance to the subsoil. The passage was used by workers of the cisterns.
In addition to the numerous vehicles and motorbikes, under 8m of debris, several statues of different periods have been found, including the funeral monument in honour of captain Aurelio Padovani, captain of Bersaglieri during the First World War and founder of the Neapolitan fascist party.
WTC 2020
The next WTC will be held in Kuala Lumpur, Malaysia. The tunnelling market continues to expand there, but the country is best known for its iconic 4km-long (road and drain section), 13.2m-diameter Stormwater Management and Road Tunnel which is a clever use of underground space that targets the dual problems of flooding and traffic management. When floods threaten, lower road decks can be closed to form a high-capacity storm drain.
The proposed theme for next year’s edition is “Innovation and sustainable underground serving global connectivity”. We hope to see you there.
