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Musk talks tunnelling concepts May 2017

Patrick Reynolds for TunnelTalk

Billionaire entrepreneur, inventor and engineer Elon Musk is expanding his interest in underground infrastructure and has outlined a three-step strategy to develop a new tunnelling system to build a network of urban road tunnels and excavate the infrastructure at a faster and cheaper rate.

Elon Musk explains his tunnel network vision
Edited excepts from TED Conference interview

Speaking on the last day of the 2017 TED (Technology, Entertainment, Design) media organization conference, in Vancouver in April, Musk said the technology would deliver the tunnelling economics needed to achieve his vision for a multi-level road tunnel network spreading out under major cities. Los Angeles, the car capital of the world, and now suffering chronic freeway traffic congestion during rush hours, is targeted as the first to undergo the transformation.

The strategy is focused on smaller diameter tunnels, more powerful boring equipment, and simultaneous excavation and lining. He believes the three-pronged combination could deliver a tenfold improvement in underground construction economics.

To develop the concept of the 3D road tunnel network, Musk advocates what he calls “a fairly straightforward series of steps” to obtain in tunnel technology improvements and reap commensurate construction cost benefits.

First, he explains, multi-lane road tunnels are not wanted. Instead, his concept is for vehicles not to be driven, but rather carried on individual electric shuttle platforms, or “car-skates”, along narrower, single lane road tunnels. To that end, Musk is looking to cut the diameter of road tunnels by at least half the current standards for a single lane road tunnel of 7.9m-8.5m (26ft-28ft) diameter, including allowance for safety, ventilation, access and emergency facilities.

Concept of a car on a skate parking space
Concept of a car on a skate parking space
for taking the access elevator to the system
for taking the access elevator to the system

“If you shrink that diameter to 3.7m (12ft), which is plenty to get an electric through,” Musk said, “you drop the diameter by a factor of two and the cross-section by a factor of four, and the tunnelling cost then scales back with cross-sectional area.”

Second, Musk is exploring design of tunnelling machines to install the lining while continuing excavation.

“Tunnelling machines currently excavate for half the time, then they stop, for putting in reinforcements for the tunnel lining,” he said. “So, if you design the machine instead for continuous tunnelling and reinforcing, that will give you a factor of two improvement.”

Third, in terms of the equipment muscle, Musk believes more can be done.

“Also, these machines are far from being at their power or thermal limits, so you can jack up the power to the machine substantially. I think you can get at least a factor of two, or maybe a factor of four or five, improvement on top of that,” he suggests.

All together, Musk believes the various changes to the technological approach to tunnelling systems could deliver “an order of magnitude improvement,” or cut about 90% off, the cost per mile to build the narrow road tunnels he envisages for his subterranean traffic labyrinth.

Musk brought his spotlight to underground technology following his public complaint (via Twitter, in December 2016) about the severe traffic congestion issues in Los Angeles. He soon added his notion to bypass – or even totally avoid – the gridlock.

At the TED event, Musk explained that he envisions toll payments would be involved, giving drivers – and ulimately driverless vehicles – access to the nested layers of road tunnels.

An animated video illustrated how the maze would be entered, and it is radically different to the current system of using long access ramps for cars to drive underground. Instead, the concept is to park on the surface on special lift shafts, capable of taking a single vehicle below ground. The vehicles would descend on special platforms, remaining securely held on the electric car-skates that would subsequently shuttle along the tunnels at speeds of up to 200km/hr (125mph), he said.

Promoting a following on twitter
Promoting a following on twitter

“You have to be able to integrate the entrances and exits seamlessly into the fabric of the city,” said Musk, suggesting that entrances and exits could require surface areas equivalent to “parking spaces”.

Musk advocated his view of the 3D network as offering “no real limit to the levels of tunnel you can have”, citing the extensive use underground levels in the mining sector.

He explained that the team at his aptly named The Boring Company has been looking at the tunnelling questions for some months. He told the TED conference audience that he spends only 2%-3% of his time on the research area and that the effort is supported with some in-house input from his team at the headquarters of SpaceX, his rocket development business. He is also developing electric vehicle technology through his Tesla Motors company. Before these ventures he made his fortune in software.

He added that the tunnelling system could have application for his sponsored HyperLoop system, which is another small tube transport shuttling system aimed at propelling loaded freight or other pods at high speed in sealed vacuums.

TunnelTalk is following also the different developments in the field of hyperloop technology and will publish news of the concepts in a coming issue of the web magazine.



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