You may or may not have heard of the revolutionary new tunnelling technology company hyperTunnel. Through a broad range of innovations, this UK-based scale-up plans to radically change the way tunnels and other underground constructions are built, enlarged, repaired, maintained and monitored. This new approach is being made possible by lateral thinking, technology transfer and digital transformation. As a result, tunnelling projects should become significantly less expensive, less time-consuming, less of a commercial risk, more sustainable and also safer.
Ambitions this big deserve an explanation. Below follows an outline of how and why hyperTunnel’s approach differs from standard industry practice, and how hyperTunnel’s new methodologies are expected to trigger developments in construction chemicals, which ultimately benefit the industry at large.
As might be expected, hyperTunnel’s senior personnel have high-calibre experience in tunnelling and civil engineering: Chairman, Mark Carne CBE, is a former chief executive of Network Rail, where he oversaw £15bn of infrastructure improvement projects, while the head of our technical board, Peter O’Riordan, is a chartered engineer who led development of London’s Crossrail 2 at Arcadis, and the London section of the HS2 high-speed rail project at CH2M. This technical board comprises senior leaders from some of the biggest names in tunnelling who monitor and advise on progress. But the company’s two co-founders, Steve Jordan and Jeremy Hammond, made it a bigger priority to recruit senior-level people without a tunnelling background, and it’s this that is unlocking ideas for technology transfer.
Jordan and Hammond first saw the need to modernise tunnelling when jointly exploring ways of generating tidal-range energy. Now their company’s vision is shared by senior-level engineers from innovation-rich industries as diverse as Formula 1, mining, oil and gas, chemistry and robotics. This means that, though many of hyperTunnel’s methods and technical solutions are new to tunnelling, they are well-proven in other applications.
PREPARATION: HORIZONTAL BORES AND A DIGITAL TWIN
hyperTunnel’s single biggest differentiator is its fundamental approach. In a reversal of convention, first the company builds the tunnel, then digs the hole. Rather than digging through the ground with a tunnel boring machine or using a traditional drill-and-blast technique, a simple horizontal directional drilling (HDD) rig is used to install a network of HDPE pipes to provide access to the whole tunnel length so that a swarm of multi-function robots can 3D print the tunnel.
Initially the HDD rig is used to take core samples along the entire tunnel path. The drill head is guided with exceptionally high positional accuracy using techniques borrowed from the oil and gas world. Unlike the usual practice of dropping vertical boreholes along the planned tunnel path up to 500m apart – a distance over which geology can change – the hyperTunnel approach provides a complete picture of the geology along the tunnel path. This can be repeated a number of times, depending on the size of the tunnel, to capture an accurate survey of the geology.
These core samples are supplemented by other sources, such as existing geological information and historic borehole data. Additional data is gathered by running a proprietary 3D ground penetrating radar (GPR) system along these bores once they have been lined with HDPE pipe (approximately 280mm OD). This GPR data is expected to have significantly better resolution and reliability than traditional techniques because of hyperTunnel’s methods of collection, meshing and antenna design. Resolution is increased by accurate and finely spaced sampling with either step frequency or multiple pulsed frequencies. To further improve survey visualisation, seismic, tomographic and thermal imagery data are also meshed together to support the definition of the tunnel profile.
Next, a series of HDD construction bores are drilled around the tunnel periphery – typically spaced a couple of metres apart (depending on the geology) – to define the tunnel dimensions and temporary workspace for construction. These construction bores are also lined and are used to gather more survey information to feed and enhance the dynamic digital twin.
These multiple layers of information are incorporated in a fully parameterised, data-rich 3D model (digital twin) of the tunnel and geology immediately surrounding it, supplemented by BIM. The result is a very detailed picture of where the geology changes, and features such as fissures, voids and water. Using VR and AR technology, it is possible to take a virtual walk through the digital twin and interrogate key features in the virtual tunnel environment.
The digital twin is used for a build simulation to optimise and tailor the construction process according to the geology. This uniquely detailed insight into the ground conditions that will be encountered during the tunnel build eliminates the risk of unanticipated difficulties, expense and usual delays during construction while ‘learning’ the geology during the build. It can also bring an end to the wastefully expensive habit of over-specifying tunnelling machinery ‘just in case’.
When all this is done, the index bore pipes are like scaffolding, ready to serve as a work ‘grid’ in the construction phase and to be populated by semiautonomous robots, which hyperTunnel calls hyperBots.
CONSTRUCTION: HYPERBOTS AND SWARM TECHNOLOGY
For construction, hyperTunnel has again transferred methods from other industries: for example, swarms of semi-autonomous robots are already used in warehouse picking-and-packing, bridge-building, and pipe maintenance and repair. And it is by sending hyperBots into each construction bore that the tunnel’s structural shell is built, with the hyperBots deploying an additive manufacturing process, which uses the same principle as 3D printing. The process of forming the tunnel shell forms a water seal to the tunnel from end to end.
To facilitate this process, the hyperBots are sent into the lined construction bores to perform a wide range of tasks; these include chamber cutting, spoil removal, micro-deep mixing cement and deployment into the geological formation of composite construction materials such as cementitious grouts or polyurea-silicate injection resins. This provides for simple but accurate consolidation through to the precise manufacturing of the finished structure, building to higher standards than those achievable in a factory on the surface.
A cartridge of the relevant construction chemistry for a specific location can be carried to the deploying robot by replenishing robots and each works to a construction plan, which determines exact deployment location, material strength, chemistry specification (different robots can carry different chemicals) and chemical volume. Using AI machine-learning techniques, the geology of every millimetre of the tunnel’s path is matched exactly to the chemistry that will best stabilise the tunnel.
Multiple hyperBots can be deployed in each construction bore, where they are able to pass each other to move freely. By using swarm technology managed by standard industry software, hundreds or even thousands of robots can work simultaneously at different locations, reducing construction time by up to 70% and cutting material waste at job sites by up to 50%.
hyperBot technology gives almost complete freedom to position deployment points, radially and axially, through the bore wall into the surrounding geology. Deployment is made via disposable drill ‘bits’ acting as conduits to the geology. The distance these can reach in the radial direction from the bore is sufficient to allow deployments or ‘plumes’ delivered from adjacent bores to intersect one another and form a continuous structure. Because the bore pipes remain useable after initial deployment, subsequent deployment operations are possible if required.
Live feedback provided by the GPR and other survey tools at the deployed plume front can be used to adapt the deployment strategy in real time, ensuring that when in-situ material is replaced with composite material, it is always of sufficient volume and structural strength. The accuracy of hyperTunnel’s surveying and deployment methods is well-suited to dealing with varying geology along a tunnel’s proposed path. This will be especially advantageous if the world’s increased need for tunnels leads to more being constructed through challenging geologies or soft ground.
DISRUPTION AND EXCAVATION: DRAGLINE SHIELD TECHNOLOGY
When the tunnel’s structural shell is complete, the original index bores are reamed-out using standard HDD techniques to facilitate a ‘slump’ of the spoil. Then the spoil is disrupted by the technique best-suited to the geology and ground conditions, e.g. hydraulic or sonic fracturing.
hyperTunnel uses a standard excavator to excavate the spoil from small tunnels and smaller tunnel enlargements. For larger projects, the company is developing a new dragline shield technology, called hyperShield, using techniques proven in open-cast mining. This makes it possible to complete the excavation in one pass. The spoil is not dug or drilled, but gathered and removed, which is much easier and requires significantly less energy.
The hyperShield is pulled along the tunnel’s path by cables that run through the HDPE pipes previously used for constructing the shell. Guided along the tunnel path with probes and controlled using camera-based visualisation systems, hyperShield is controlled by operators located outside the tunnel. This greatly reduces human risk. At no stage during preparation, construction, or excavation is it necessary for people to enter the potentially dangerous environment of the incomplete tunnel.
An array of tools mounted on the leading edge of the hyperShield cut the precise interior shape between the HDPE pipes, defining the tunnel profile and base dimensions. Loose debris is scooped up, channelled through the back of the hyperShield excavator, and removed by autonomous electric trucks cycling under the type of drop-box loader routinely used to fill wagons with ore or coal. The hyperTunnel method also reduces the amount of spoil that needs to be removed because the tunnel shape can be customised and is not limited to circular profile – which is often larger than required. And, because the spoil has not been crushed or chemically treated for transport out of the tunnel, it is in a much better state for recycling and immediate reuse.
The hyperShield can also prepare and incorporate systems for the installation of a secondary lining during the final phase, completion.
COMPLETION – THEN MAINTENANCE
The completion phase of hyperTunnel’s method entails the installation of tunnel linings, if required, and of equipment such as sensors to continuously monitor the tunnel for predictive maintenance.
Once the hyperShield has excavated the disrupted material, other machinery such as robotic sprayed concrete lining machines or slip formers can follow it through the tunnel to install the type of secondary lining that meets the need of the tunnel application. Depending on the geology, the hyperTunnel method may provide the opportunity to use non-sacrificial bores for additional strengthening, for monitoring technologies, or for use by third-party services such as fibre optics.
Because a digital twin of the tunnel has been created, handover of the tunnel is simplified. The data gathered to form the digital twin (logged using blockchain encryption) also serves another important function as a ‘single truth’ database of construction details. This will enhance asset maintenance and management by increasing operating efficiencies with the capability to simulate many operational scenarios and the significant environmental benefits that brings. Through AR and VR, engineers will be able to see not only the tunnel’s construction and surrounding ground, but also the exact location of hidden service facilities such as cables and wires, speeding up future works by eliminating time consuming geology and utility surveys.
MATERIALS: CONCRETE WILL CHANGE
The introduction of these new methods will also change the way concrete is used in the construction of tunnels and other underground structures. More than just being a commodity building material, concrete will become a key element in the construction method. It willl drive developments in a new generation of more sustainable, low-carbon solutions in concrete and injection materials. This is being led at hyperTunnel by Dr. Sven Asmus, Director of Chemistry & Materials, who was previously chief technology officer at MBCC Group (formerly BASF Chemicals).
In traditional tunnel building, construction chemicals are used in the production of relatively high-strength tunnel segments, sprayed concrete linings, and polymer or steel fibres as reinforcement. But with the new in-situ method, quite different compositions of concrete are required, which in turn means different construction chemicals.
Though existing chemical technologies can cope with all standard concrete compositions, requirements with regard to the rheology of the concrete might well be dictated by the deployment mechanics of the robots. Total performance control of the concrete, including flowability, will be of utmost importance. Innovations will be desirable, particularly around optimising the pump capabilities of the robots. hyperTunnel is investigating polyurethane resins (PU), polyurea silicates (PUS), colloidal silica, acrylic resins and chemically-modified cement grouts. Epoxy resins will be less of a focus because of environmental concerns.
New chemical mixes will certainly be needed in the concrete admixtures. With low-clinker cement desired for this method, countermeasures will be needed to achieve total performance control. In another key difference from conventional methods, the in-situ method could predominantly use poly (aryl ether) technology or comparable performance chemicals for the low viscosity concrete deployed by the robots. The chemistries of set retarders and set accelerators, including hardening accelerators based on calcium silicate hydrate seeds, also need to perform at the highest levels.
Another advantage of the in-situ construction method is that it can accept longer concrete hardening times, adding flexibility. This is an open-door invitation for the reduction of clinker content, probably to less than 10%. This reduces CO2 footprint even if using the same volumes of concrete as in conventional construction methods – but concrete volumes will be reduced by about 50% because chemical deployment can be altered in accordance with changing rock conditions along the tunnel’s path. Also no overcut, as required by current machinery, means no extra concrete to fill in the gaps with grout. Though superplasticisers have been more widely commercialised in recent years for alkali-activated cement (AAC) and low-carbon concrete, these too will have to be upgraded in a way which ultimately benefits many construction businesses.
COMMERCIALISING THE CONCEPT
Revenue generation includes licensing and systems integration expanding into the supply chain through component manufacture. Licensing forms the majority of the organisation’s focus, and revenue is based on significant investment to date in patented intellectual property and characterised by high margins akin to a software-as-a-service (SaaS) business model.
The company expects to start with smaller scale tunnels and repairs before growing to mega projects. It is currently conducting testing on scale tunnels at its R&D site in Hampshire, England. The latest tunnel employs all aspects of the hyperTunnel methodology, including surveying techniques, robotics, deployment tools and monitoring processes. Lifesize simulations are being run on a typical cross-passage of the type that will be needed 100 times by HS2 and 27 times by the Lower Thames Crossing.
Ahead of the first new tunnel build, hyperTunnel will be involved in further proof of concept on live sites together with specific partners, as well as on refurbishment projects. The company has a contract to work with Network Rail on non-disruptive tunnel repairs for the maintenance and improvement of railway infrastructure, which includes approximately 650 Victorian-era tunnels across the UK.
hyperTunnel’s methods are expected to bring cost and delivery-time improvements, as well as reducing inconvenience for passengers. The company is in discussions with project leaders in the Middle East, USA and Canada. In time, hyperTunnel expects its IP-protected system to become a core part of how the world’s biggest tunnel builders and maintainers operate.
