Mike Baier(@Mike__Baier):On hard-rock machines like Prufrock Main beam, the propulsion system doesn’t push off a tunnel liner — because there is no liner. The rock itself forms the walls. Instead, Prufrock Main beams grip the tunnel walls with ~4 million pounds of horizontal force. Think of bracing yourself hard against both sides of a narrow hallway and then pushing forward. That’s the principle. By gripping the rock directly, we delete entire subsystems: no liners, no erectors, no segment handling, no grout. The result is counter-intuitive: the maximum theoretical tunneling speed through hard rock is significantly higher than through soft soil. Simpler machine. Faster progress

2026.08.14 15:08

On hard-rock machines like Prufrock Main beam, the propulsion system doesn’t push off a tunnel liner — because there is no liner. The rock itself forms the walls. Instead, Prufrock Main beams grip the tunnel walls with ~4 million pounds of horizontal force. Think of bracing yourself hard against both sides of a narrow hallway and then pushing forward. That’s the principle. By gripping the rock directly, we delete entire subsystems: no liners, no erectors, no segment handling, no grout. The result is counter-intuitive: the maximum theoretical tunneling speed through hard rock is significantly higher than through soft soil. Simpler machine. Faster progress