For decades, engineers seeking to build tunnels underground have relied on huge tube-like machines armed with a frightening array of cutting wheels at one end—blades that eat dirt for breakfast. These behemoths, called tunnel-boring machines, or TBMs, are expensive and often custom-built for each project, as were the TBMs used to excavate a path for London’s recently opened Elizabeth Line railway. The machines deployed on that project weighed over 1,000 tons each and cut tunnels over 7 meters in diameter beneath the UK capital.
But British startup hyperTunnel has other ideas. The firm proposes a future in which much smaller, roughly 3-meter-long robots shaped like half-cylinders zoom about underground via predrilled pipes. These pipes, around 250 millimeters (10 inches) in diameter, would follow the outline of the proposed tunnel’s walls. Once inside them, the bots would use a robotic arm topped with a milling head to penetrate into the surrounding earth and carve out small voids that would then get filled with concrete or some other strong material. Piece by piece like this, the structure of a new tunnel would come together.
“We’re talking about thousands of them,” says hyperTunnel’s director of engineering, Patrick Lane-Nott. “Much like an ant colony or a termite colony works in swarms.”
A video released by the company includes a 3D animation of the robots beavering away on some imagined subterranean structure of gargantuan proportions. But it would be rather like building tunnels in reverse. With a TBM, you first dig the hole and then add supports or walls to keep the remaining earth surrounding the void at bay. “We put the tunnel in the ground—and then we dig the hole,” says Lane-Nott. Once the structure has been built, the material filling the tunnel’s chamber can be removed.
One advantage of this, he argues, is in using less building material overall. Instead of placing standardized sections of tunnel wall along the entire length of the project, the structure’s outer thickness could vary to suit the actual geology and pressures surrounding the tunnel at any given point.
Tunneling experts who spoke to WIRED agree that the industry is crying out for technological solutions to lower costs and heighten efficiency—it can take years to design and build a TBM and then actually dig a tunnel with it, for example. A suite of new companies promising to shake things up is emerging—from Elon Musk’s Boring Company to hyperTunnel and firms developing new high-temperature methods of blasting through the toughest rocks on Earth.