As a disruptor, Elon Musk is continually making waves. In successfully completing operating tunnels for Tesla cars in one year below the Las Vegas Convention Centre, his Boring Company has demonstrated its intent on improving current mechanised boring technology. He has thus thrown down the gauntlet and challenges the tunnelling sector.
Although of relatively modest diameter and length, the Loop tunnels’ completed in Vegas could be the first step in achieving his stated objective of ‘beating the snail’: building tunnels ten times faster and cheaper than is possible using current technology and techniques.
For Musk, current technologies are unlikely to produce the network of tunnels at the rate (and cost) necessary to cater for the loop and hyperloop networks that will allow ultra-fast regional travel. Achieving the high-speed travel of the future will therefore require quantum leaps that are typically only made possible by a transformation in existing technology and the associated costs; for Musk, current tunnel construction costs are prohibitively expensive, with many projects costing between US$100m and US$1bn per mile. Therefore reducing tunnelling costs “by a factor of more than 10” would be a prerequisite to achieve the tunnel networks of the future. So, what better way to foster innovation than by running a competition – a tried and tested method of brain storming.
Having inspired bright young things globally, Musk’s Boring Company held the final of its first competition in Las Vegas in September 2021, an event that is intended to be held annually in order to generate new ideas for boring technology
The competition was a success, attracting entries from some of the world’s top universities including, MIT, TUM, Warwick and ETH Zurich, not to mention from a variety of industry tunnelling professionals. Nearly 400 applicants from around the world submitted their proposed solutions with the ultimate hope of claiming one of the accolades.
To enter, teams were required to submit a preliminary design for a tunnel boring machine (TBM) in October 2020. Typically, this would have been a roughly 30-slide PowerPoint presentation detailing how the teams would build their machines. Once technical reviews of the submissions were completed, teams learned by the end of 2020 whether their designs were successful and if they would progress to the next round.
Then, following a series of technical reviews and progressions through several selection stages, the 400 were whittled down to twelve finalists – teams from six countries – the US, UK, Germany, Canada, Switzerland and India. They would compete to see whether their individual designs could achieve the competition requirements: to drill a 500mm-diameter tunnel of length 30m as fast and as accurately as possible.
Clearly it was no easy task: although it was possible for the teams to bore the 500mm-diameter tunnels and line them to enable self-support, no team achieved the full 30m target length, although some managed to get close to it.
Although designs differed markedly, all the teams had to begin from the surface digging down diagonally to the required level, thereby saving the time that would normally be required to dig launch and reception pits.
Once the final had run its course, five teams were victorious:
? Overall winner: TUM Boring
? Best guidance system: TUM Boring
? Innovation and design: Swissloop Tunnelling
? Team safety: UMD Loop
? Fastest launch design: The Diggeridoos
TUM BORING
Judged as the overall winner, the TUM Boring team comprised students supported by the Technical University of Munich in a crowd-funded initiative, like many of the finalists. Interestingly, the TUM team had already won previous SpaceX Hyperloop Pod Competitions hosted by Musk in California which, as the name suggests, were more about designing and building the pods for hyperloop rather than the machines to bore the tunnels.
TUM’s design for this latest Musk venture combined established techniques such as pipejacking with multiple innovative approaches. As the TBM excavates, segments of pipe which form the tunnel lining are jacked into position from a revolving carousel-type system which allows sections to be rotated sequentially into place.
The technique is claimed to have several advantages, including fast tunnelling feed rates, robust pipe segments with pre-installed driving surfaces, and considerable use of off-the shelf components.
The laser-guided, hydraulically-steered machine had a fairly conventional water-cooled, motor-driven cutterhead with auger. Propulsion was provided by a jacking system involving two clamps each powered by four hydraulic cylinders. In continuous mode, the jacking system is said to provide forces of up to 500kN; in discontinuous mode (used only as a back-up) this increases to 1MN. In their research, the team members had established that 500kN would be sufficient to tackle the soil in Las Vegas. Spoil removal was achieved by an auger conveyor allied with conveyor belts integrated into the pipes used to create the tunnel structure.
SWISSLOOP TUNNELLING
Founded in late 2020, the Swissloop team was the official team of ETH Zurich and comprised over 40 students. Their expertise spanned mechanical, civil and electrical engineering, as well as various business-related fields. Some of the team members had also participated in the SpaceX Hyperloop Competition of 2018/19 and then, as now, had won second place and received the award for innovation.
The distinguishing feature of Swissloop’s ‘Groundhog Alpha TBM’ was the lining system which allows the in situ fabrication of the tunnel structure. The concept involved a 3D-printed, 15mm-thick tunnel wall made of glass-fibre lamellas and a two-component polymer mix to ‘ensure structural integrity along the whole length of the tunnel’. Lining is created continuously with excavation, with 16 hydraulic cylinders bracing against the tunnel wall for an uninterrupted movement under a propulsion force of 200kN.
The 7m-long, 0.56m diameter TBM featured a cutterhead as part of an ‘erosion system’ with a cutting wheel that extracted large stones. These are subsequently crushed to centimetre-wide pieces and flushed out of the chamber in a slurry under 10 bars of pressure, assisted by a Venturi vacuum pump. Pushing off from the newly-created tunnel wall is achieved by two discontinuous hydraulic grippers. Weighing around 2.5t, the machine was capable of achieving a torque of 8.5kN, rotating at 27rpm and had a 100kN pushing force. Steering was provided by a hydraulic ‘hexapod’ system comprising six hydraulic cylinders that are designed to gave six degrees of steering precision. The machine’s target speed was 1cm/sec.
UMD LOOP
The UMD Loop team comprised more than 50 engineering, maths, computer science and physics students – all undergraduates – from the University of Maryland, US. They were not new to such events, having competed in SpaceX’s Hyperloop Pod competition in the past and came fifth; upon graduation, some of the students were hired by companies such as SpaceX, Tesla and NASA. Nevertheless, designing a tunnel boring machine was a totally new experience.
Entering these competitions is not cheap, particularly for a bunch of college students: the TBM alone cost around US$200,00 to design and build, and travel costs for the students from the East Coast to Las Vegas was in the region of US$20,000, paid for through sponsorships, crowd funding and the generosity of the University of Maryland.
THE DIGGERIDOOS
Comprising a 17-strong team of engineering and business students from Virginia Tech, US, the team won the fastest launch design accolade in the competition.
UK TEAMS
Given the very strong competition, and having achieved finalist status, none of the UK teams were successful in the final. Warwick Boring was one of those teams. Technology aside, the team produced some of the best renders of the competition.
As yet another student-led project, this time based at the University of Warwick, England, the Warwick Boring Team (WBT) designed, created and built a highly sustainable tunnel boring machine.
The team’s aim was to make future transport greener, cheaper and faster with their novel design. Support came from the School of Engineering, Warwick Manufacturing Group (WMG), numerous other industry sponsors and the University of Warwick.
At the heart of the design was a cost-efficient technology that would be easy to assemble and which used fewer components compared to conventional TBMs. Furthermore, development was carried out with ‘design for manufacture’ (DfM) in mind which puts a premium on designing components and systems that are easy to produce and result in a better end product. This can result in successful scalability in future commercial projects.
WBT said that its machine, once scaled up, was designed to be “80% faster than standard machines that typically dig one mile in 8-12 weeks”. Its aim was to dig at a cost that is 10 times cheaper than traditional machines that typically result in tunnels costing anything between US$100m – US$1bn per mile to construct.
During its excavation mode, the machine uses a bentonite slurry to remove spoil from the cutting face. But, the team said, unlike other designs used in the industry, it had developed a slip-form tunnel-lining solution to allow a continuous propulsion cycle and leading to greater simplification of the tunnelling process.
WBT’s final design was accepted by the competition organisers in February 2021 for participation in the September event in Las Vegas’
Sanzhar Taizhan, founder and co-project lead at Warwick Boring commented:
“After almost a year of creating, designing and building we are thrilled to see the machine here in the flesh, finished and finally in Vegas competing. The entire team has worked flat out for the last few months to get it together – once we were allowed in the labs after the COVID-19 restrictions eased.”
Tanner Hatzmann, the technical director at Warwick Boring added:
“It would typically take years to create, design and build a novel machine, however we have been able to do it over the last year, even during lockdowns. The Warwick Boring tunnelling machine is exciting as it has unique features”.
BIGGUS DIGGUS
Also from the UK, this team comprised engineering professionals working within the tunnelling sector, mainly alumni from the University of Warwick’s Tunnelling and Underground Space Specialist Postgraduate Programme. It also included engineering students from Imperial College, London and the University of Alabama, as well as M&E engineers from various organisations.
In 2018, Elon Musk proclaimed that “our competitions attract the best students in the world.” Clearly, he was not far out, judging by the interest and results created by this event. As the competition is intended to occur annually, it is to be hoped that it will throw up more technology that can be commercialised and used to beat the snail. But that may not happen for some time.
