Construction and tunnelling are making use of Building Information Modelling (BIM) to boost performance but it is only an appetiser for what is coming – digital twins. While BIM is a virtual, information-based copy of a project structure, digital twins will encompass those models and go further with live link-ups to physical assets updated through real-time data flows.

To progress from BIM to digital twins, the greater vision for digital infrastructure for the UK is not ever-greater centralisation of data in one place but more of creating clusters of models connected in networks – accessible as required. Like the advances in computing that make BIM possible, the digital twins and networks will rely on other parts of the rapidly advancing digital technologies outside of construction, such as smart objects (Internet of Things, IoT) and super-fast telecoms (5G and beyond).

Those are the broad brush strokes of the things expected to come soon, but nailing down precisely what a digital twin is – and BIM too for that matter – presents ongoing challenges. For advocates of digital transformation, it is not always an easy sell, and for those who dive in, or stick a toe in the water, they find the choices are many, and open. Much lies in the eye of the beholder.


According to the US-based Digital Twin Consortium, the anticipated digital twins market size is expected to be 15 times bigger within five years. The UK, too, is urging greater use of the technology, pursuing a National Digital Twin Programme which was initiated after a report (Data for Public Good) by the National Infrastructure Commission, four years ago. The government wants digital environments, and shared data, to boost the UK’s infrastructure and built environment.

Development of the NDT Programme is led by the Centre for Digital Built Britain (CDBB), based at the University of Cambridge, and the Digital Framework Task Force. According to the NDT Programme update report, in 2020: “The defining characteristic of a digital twin is its data connection to the physical world, which can be updated to inform decision-making.”

The reports says digital twins should be data-rich, enough to look back, for retrospective analysis, and ahead to do scenario planning. The outcomes are meant to give enough helpful insights to save money, time, resources and boost efficiencies over the life and development of an asset. Even more benefits are anticipated when the systems are scaled across networks of digital twins.

Networks are the bigger picture being pursued in the UK by the NDT approach, which aims to create an “ecosystem” of digital twins, or “cyber-physical fabric”. Basically, beyond their creation by BIM, physical infrastructure assets of the future are to be hooked up live to computers which act as their ever-watchful brains. The aim is to help monitoring and planning across entire sectors, and also over the assets owned by large organisations.

The change is significant – and in process. It is generally accepted that the Covid-19 pandemic has accelerated moves toward acceptance of more digital environments and support. Given that approaches to and interpretations of BIM and digital twins are varied, CDBB earlier this year published the Digital Twin Toolkit, to support the NDT Programme, and which outlines key areas to look at when developing digital twins.

A number of clients, projects and supply chain players are already engaging with digital engineering approaches with a view to create tunnel projects and other infrastructure.


Digital engineering is a key aspect of the UK’s new HS2 high-speed rail line on which tunnelling for the first phase began recently. Phase 1 – between London and Birmingham – is partly underground with long stretches of TBM-bored tunnels.

“BIM has been central to HS2’s development from its earliest days and was used to develop the hybrid Bill scheme,” a spokesman for HS2 Ltd tells T&TI. “Our main contractors are all contracted to utilise BIM and the wider applications of digital engineering to improve design and project delivery.”

The spokesman added: “With an ambitious vision to develop a digital twin of the railway, we are pushing beyond the government’s BIM mandate to capitalise on latest technological trends, with BIM at its core.”

PCSG, a subsidiary of Bentley Group, is supporting HS2 Ltd on a programme-wide basis with the development of a digital twin of the entire rail system. It is using its cloud-based GeoConnect+ system to hold data accessible for design and construction teams, including BIM, health and safety, and environmental information.

For PCSG, digital twins are ‘mirror systems’ with the distinguishing feature, beyond traditional 3D models, of being connected with the physical asset, with real-time data-flow being the key.

With Phase 1 continuing over the next few years, and further phases planned for the future, there is much scope for HS2 to continue to make significant advances in applying digital engineering.


Transport for London’s (TfL) 1.4km-long Silvertown road tunnel under the River Thames is being constructed by the RiverLinx consortium under a PPP concession contract (design, build, finance, operate and maintain).

The consortium includes BAM PPP-PPGM JV, SK Eng & Construction, Macquarie Capital, Cintra, and Aberdeen Standard Investments. Design and construction input is by BAM Nuttall, Ferrovial Agroman and SK E&C on a turnkey basis, with the tunnelling contribution coming from Wayss & Freytag.

With early main construction underway, piling is almost complete for the TBM launch chamber for which excavation has started, a spokesman for TfL told T&TI. He added that the TBM is due to arrive in Spring 2022.

Asimina Makrynioti, TfL’s programme BIM manager for Silvertown Tunnel tells T&TI. “Across TfL, we are adopting BIM and digital engineering into our major projects as it helps both improve the collaboration between the project stakeholders, as well as provides additional assurance that the design solution is coordinated and integrated before it is built on site.”

Makrynioti adds: “Having a digital representation of an asset once it is constructed means we can improve decision-making and introduce further efficiencies during the operational stage.”

RiverLinx is creating 3D models of the assets, ensuring they are kept up to date, that its supply chain design is integrated, and that changes on site are included.

“These are used to improve design coordination, identify programme efficiencies, calculate carbon footprint and suggest health and safety improvements,” Makrynioti says. “The data will also then be passed onto TfL and the operations contractor once the tunnel is completed and available for use. All assets will also be tagged with a unique ID that will enable linking with the asset management systems and improve maintenance activities.”

Makrynioti says further: “The project is BIM Level 2 and is not currently digital twin. However, the work being undertaken now will be able to act as a potential enabler for a digital twin in future.”


Germany has been making significant inroads with digital engineering for the past few years, with implementation of BIM a key part of the strategy, not least on rail company Deutsche Bahn’s (DB) new projects. The move is part of a wider national drive toward digitalisation led by the Federal Ministry of Transport and Digital Infrastructure (BMVI).

“BIM is a new level of planning and implementation of infrastructure projects,” a DB spokesman on DB’s 2nd Core S-Bahn project in Munich tells T&TI. “Using the BIM method, DB can deliver a new degree of quality for planning and implementation of services throughout the entire lifecycle of an infrastructure-related facility.”

The 2nd Core S-Bahn project is a 10km major addition to rail capacity in Munich and runs mostly deep-level below existing stations. The 7km underground section of twin-tube tunnel connects the central station (Hauptbahnhof) with Marienhof and Ostbahnhof stations, and passes under metro lines to depths of 40m. Complex, large-scale new station works are also involved in the heart of the city.

DB has been advancing its approach to BIM in a three-step strategy since 2015: 1) Pursue goals set by BMVI but consolidate activities and standardise by 2020; 2) By 2025, boost expertise through the supply chain and pilot the taking of digital into operations and maintenance; 3) Beyond 2025, accelerate digital take-up to all projects.


Norway’s transport authorities are not yet using digital twins, as such, and also have their own approach to digital models – not exactly BIM, so far, but partly so.

BIM is a ‘linguistic concept’ as it is not precise and so is open to interpretation, according to Statens Vegvesen (NPRA), the national roads authority, in discussing its V770 Model-Basis which is its main preferred tool. V770 can be considered as taking a part-BIM approach.

Road projects involve fewer standardised objects and elements, compared to building structures, and the V770 system allows bespoke fitting of models into local landscapes. The BIM-in-part V770 guidance to industry was established in 2015 after collaboration with industry, and also the rail authority, Bane NOR. In the fast-moving digital engineering landscape, though, it is being updated.

Project manager Harald Inge Johnsen tells T&TI that the V770 system is being used as part of the development of the Alesund-Molde road project, which is a key component of the E39 West Coast Highway. The aim is to build a series of tunnels, the largest being a twin-tube 14.5km crossing below a fjord, plus large bridges, from 2023, depending on final planning and funding approvals. SDeveral industry meetings to brief contractors on the latest plans for procurement recently got underway.

Also for the E39 highway, but farther south, the roads authority is getting underway with main construction of the Rogfast twin-tube tunnel to make the world’s longest subsea crossing, at almost 26.7km length. Digital engineering also features in those plans with use of V770 and BIM, a project spokesman tells T&TI. Early works have been completed and principal tunnel works on the first of three main lots are to start later this year.


Globally, many other underground and infrastructure projects involve BIM, even if universality has yet to come, and digital twins remain some way off.

“Digital twins can be used for a variety of use cases and the level of detail depends on the case,” contractor Implenia’s head of BIM civil engineering Felix Stauch tells T&TI. He continues: “A huge advantage of digital twins is the ability to structure and organise information.”

Stauch notes that the pool of data can be examined either visually or through interrogation as a database, or both. But common standards, effective data storage and compatibility with future software are all necessary to ensure ongoing success of the digital environment.

He adds that to shift from BIM to a digital twin, the BIM model used to enable construction can be adapted according to the needs of the digital twin’s purpose and plans. These aspects will include choices of information structures and representations of geometry, reflecting the level of detail (spatial and time intervals) both available and wanted in future. One such adaptation was an as-built model of tunnel segments, and drew upon data recorded by the TBM.

Stauch explains that in current tenders, he is seeing a definite trend towards specific levels of detail regarding the as-built models being requested by clients. BIM turned out to be a key factor in Implenia securing the Lysaker-Fornebu rail tunnel project, in Norway. “We aim to put the model in the centre of our construction process and record all relevant data,” he explains. “This is the basis for a digital twin.”

Consultant Amberg has also worked on a number of projects requiring BIM, including planning improvements for the Cornberger rail tunnel, in Germany, in which up to 5D simulations were used, T&TI is told. Automatic object and edge detection are key aspects to get efficiency in its as-built modelling, and have the ability to analyse point clouds of scanned data automatically.

For the Ceneri rail tunnel through the Swiss Alps, Amberg captured a complete data model, from machine parameters to geology, with everything geo-referenced. The consultant also did BIM studies on Swiss Railway’s (SBB) Bozberg tunnel, which Implenia bored.

Benefits of the digital approach can also be found in sub-sets of projects, such as equipment systems.

For construction of the 14.6km-long, 4.5m ID Central Interceptor project, in New Zealand, contractor Ghella tells T&TI that the mould/carousel to manufacture the 335mm-thick, 1.6m-long tunnel segments, and TBM boring, involve digital approaches supported by Italy-based Digitalnology.

Contractors Strabag and Zublin are trying to implement digitalisation to support greater work safety in tunnels excavated for the Chilean mining sector, where they have been active for more than 30 years, a spokeswoman tells T&TI. They have a range of automated remote-controlled equipment to remove and wedge rock, take images, determine presence of faults and do 3D modelling.

Digitalisation is being used in attempts to find solutions to the age-old problem of shallow excavations striking buried utilities. This has been a focus of studies in the UK to establish a National Underground Assets Register (NUAR). The project estimates that accidental, shallow-depth strikes cost the economy L2.4 billion (US$3.28bn) annually from knock-on effects but NUAR could help give L350 million (US$479m) a year in benefits alone.

NUAR is supported by the UK government’s Geospatial Commission, for it believed the current system “is unlikely to reform itself,” as reported by the Centre For Digital Built Britain (CDBB) in a case study of the pilot project. The initiative is another push from the centre to catalyse change as part of the UK’s wider national infrastructure and geospatial strategies.

CDBB reported on the pilots that digital technology is an enabler but not key to success, which instead was down to commercial owners sharing data and wanting it held securely.

“Basing the platform on a standardised data model, based on an evolving international standard, will be key to extensibility and interoperability with other initiatives,” NUAR’s stakeholder engagement lead, Holger Kessler, tells T&TI.

Data on deeper depths, related to geology and geotechnical concerns, such as from boreholes, is not presently in the scope of NUAR but, says Kessler: “It is the subject of future use cases”.

The geospatial work is part of a wider effort to create national digital ecosystems, drawing upon an information management framework, to encompass three elements: foundation data models; a reference data library; and integration architecture – or plans for sharing, languages to do so, and ways to link it all up.


“Building information models are great but usually tied to text-based interlinking features,” Nicolas Waern, CEO of Sweden-based AI/digital strategy consultancy Winniio tells T&TI. “It’s hard to ask the digital twin what needs to be done and it’s usually not possible to do work with AI in an easy way.”

“BIM has not been known to absorb reality when it comes to real-time data either so that makes it hard to transition into the lifecycle perspective,” Waern says. He adds: “Most of the time, all that wonderful information and data that have been created during the construction phase gets lost in translation.”

However, challenges for engineers are increasing, Waern believes, through combined waves of change around sustainability, demand for transparency, use of digital engineering and AI, and the advent of interconnected real-time data flow and IoT. All these things combined point to even greater usage of digital twins, he concludes.

“Digital twins are just a tool and a means to solve real-world problems faster,” he says. From his perspective, digital twins should “cater to the past, present and future,” and have the ability to absorb reality as it is, including industry standards, and invite innovation on a global scale. He adds, the technology should be able to “ingest context and display it in understandable ways for both humans and machines”, while catering to real-time systems.

Waern says: “If done right, in the right order, we see that we can accelerate decision-making over traditional methods, and that is only using digital twins focusing on people, not utilising AI.”

Digital technologies are coming into play powerfully and call for collaboration as well as more understanding about data, its control and perhaps its fundamental ownership. The changes that are coming are like ground tremors coming ever closer from distant tunnelling blasts.