How is technology facilitating better tunnelling?

As NCE has reported extensively in recent years, tunnelling is a growing sector globally and the diversity of tunnelling work is growing too. In addition, technical and data complexity continues to rise, particularly due to geological uncertainty and interdisciplinary coordination. NCE speaks with experts about how technology is facilitating better tunnelling.

Around the world, tunnelling has always been a solution to some geographical challenges, including the need for infrastructure capacity in urban environments. Increasingly, it is also a solution to some political challenges, with subsurface infrastructure being more palatable to some communities or protected areas than visible overground infrastructure. We also see growing reports that biodiversity and other environmental impacts are adding to the demand to bury infrastructure underground.

That said, tunnelling remains one of the most capital-intensive and risk-sensitive areas of construction. Delays and cost overruns can exacerbate that, often brought about by discovering unexpected geological conditions during tunnelling. And with growing numbers of specialisms involved in almost every project, there is an added complexity of project teams being more diverse not just in technical specialisms, but in the number of companies involved and the number of locations they are based in.

Ageing tunnels in Italy

There is also an ever-expanding stock of ageing tunnels that need retrofitting and expansion, which can raise its own challenges for the tunnelling profession. That is something Italy is grappling with, with more than 2,500km of tunnels criss-crossing the country.

Tunnels built during the 1960s and ‘70s enabled a practical pathway for transport links to negotiate the country’s rugged, mountainous terrain. However, they may now be in need of significant interventions, including more extensive assessment and rehabilitation work to ensure they continue to comply with the relevant Italian guidelines.

Tecne Systra-SWS Advanced Tunnelling bears the responsibility of carrying out the required assessment and rehabilitation work, and Systra head of BIM and digital services Alessandro Menozzi notes the complexity of this work.

“The assessment phase involved managing a huge amount of data from inspections, investigations and different types of service. Interpreting this complex and sometimes fragmented information is far from simple and is the basis of our design. So, it is here where there is a huge need for digital engineering approaches and standardised and reliable procedures to make sense of it.”

By using 3D geological models for the borehole TV camera, flat jacks and core drilling compression tests, the team were able to integrate and evaluate the survey data into a central model produced with Open Tunnel Designer.

This reduced the time required for interpretation of the existing tunnel conditions by around 30% compared with traditional methods.

Menozzi also says it leads to better and safer design, and perhaps most importantly, helps to improve the understanding of uncertainties that can create challenges for any projects.

“An important aspect to this approach is that we have centralised and digitised all the data. We can evaluate all the data we have and distinguish between factual data and non-factual data. That is helpful for our design proposals, as we can treat uncertainties as something that we can measure.”

Client buy-in

Ineco BIM geologist Héctor Salcedo Gutiérrez has seen similar value with the company’s adoption of new technologies for new projects.

Ineco worked on the Rail Baltica project and began by using ProjectWise to establish a connected data environment. This allowed team members to contribute to the international project from different physical locations, and it gave Ineco the confidence that all information was correct and up to date when using it.

“We integrated geotechnical and geological information into the BIM methodology,” explains Gutiérrez, who has seen different software packages integrate into their operations. “We modelled 94km of the project with Leapfrog, and then used OpenRail to model soil treatments. We then used OpenBuilding to integrate geotechnical information into the whole BIM model.” This workflow demonstrates how Seequent’s Leapfrog and OpenGround solutions integrate seamlessly with Bentley’s BIM environment. That is valuable because inter-operability can help ensure data consistency from subsurface modelling to design delivery.

Next, they used OpenGround and Leapfrog to model the site environment, helping them to determine the optimal designs for the terrain. “There was a lot of information across 94km of route. There were 1,284 field tests, boreholes and so on. So, we needed to model this.”

But while Rail Baltica encouraged this technical approach, that isn’t always the case. “At first, clients sometimes didn’t see the case for the inclusion of geotechnical information in BIM models,” explains Gutiérrez. “But over time they’ve started to realise that it makes sense not to keep these separate. I think in the last two years, we’re seeing more clients include geological information in the whole project.”

Systra Subterra has deployed digital subsurface mapping across numerous projects and is working on the development of metro lines in Barcelona, Bucharest and Dubai, high speed rail in northern Spain, and an underground highway in Santiago, Chile.

Systra Subterra technical director Ero Vinicius Silva Espiña notes that for linear infrastructure, the key to success with technology is its role in information sharing.

“We have prepared our tools to collect information in the right form to input into Leapfrog easily. So, the moment we get the information from the people collecting the data on the ground, it’s not difficult to introduce the information and make it available quickly to projects teams.”

Not that this is universally applied by others, he notes. “One challenge is that some do not use the information, which is why I don’t like to separate models. For me, the geological and structures teams are not separate teams, so their information needs to work together.”

This approach was born of necessity, explains Espiña. “We had a lot of information and the only way to ensure it could be used properly was to move away from old ways of working and build a very good 3D model. We began collaborating with Leapfrog specialists to link geological and numerical models, and once this integration became clear, we pushed to fully adopt the approach.”

Ayesa head of ground engineering and tunnelling Claudio Cabral Dias had a similar experience. Ayesa worked on the Silvertown Tunnel and is now working across Porto Metro in Portugal.

“We identified a problem with the way we were doing work – lots of repetition, lots of tedious work. Geotechnical cross sections were done by hand, scanned and put into CAD. If something changed you had to do it again. So, we wanted to get something smart as software was becoming more powerful and we had some people who moved us forward. Then Ana came along.”

Ana is Ayesa geotechnical engineer Ana Marina Sanchez de la Riva, who had previously worked in mining.

“I came from a mining company and thought that the technology used there could be highly beneficial for underground works. We can build full 3D models and export data smoothly, integrating all the work and calculations, which really helps project teams. Things were starting to move forward with BIM regulations in technical engineering, and with a Leapfrog model it’s easy for geotechnical engineers to become part of the buildability conversation in underground projects.”

Dias is clear, however, that this is still a decision pending for many companies. And he has advice for them. “I think taking the risk of changing your workflows and processes within the company is worth it. We have so many challenges so the greater risk is to continue with the old ways of working and wasting time on repetitive tasks. Instead, we embraced the challenge and embraced the change.”

eBook: The collaborative workflow for tunnels