England used a 197-foot German shaft-boring machine instead of explosives and workers to cut a mine beneath a national park; the remote system has reached 2,966 feet, with 2,283 feet still to go

Sinking a mine shaft traditionally means sending workers to the bottom of an increasingly deep hole, where they drill into rock, use explosives to break it apart, and clear the rubble before repeating the process. At England's Woodsmith mine, that cycle has been replaced by a 197-foot-tall German machine.

The Shaft Boring Roadheader, or SBR, built by Herrenknecht, cuts the shaft mechanically while crews work from platforms above the excavation. According to an Anglo American report, the Woodsmith service shaft has reached 2,966 feet below the surface, leaving 2,283 feet before it reaches its planned depth.

The machine is working beneath the North York Moors National Park in northern England, where Anglo American is developing a mine to extract polyhalite, a natural mineral fertilizer.

The machine cuts the shaft layer by layer

The SBR does not use a giant drill bit. It carries a rotating cutting drum on the end of a telescopic boom and works across the bottom of the shaft in repeated passes.

Herrenknecht says the first cut goes about 8 inches deep. The drum then sweeps from the center toward the shaft wall until a complete layer of rock has been removed.

After five cycles, the shaft is about 1 meter, or 3.3 feet, deeper. The machine is then lowered by the same distance and the process begins again.

A pneumatic mucking system removes the loosened rock. It pulls the cuttings from the shaft bottom into a suction tank before they are carried to the surface.

Crews work above the cutting face

The SBR is a 197-foot-tall suspended structure with 12 work decks and two service platforms above the cutting boom.

While the drum cuts through the rock, crews on the platforms can line the newly excavated shaft with shotcrete, bolts or concrete segments.

The Woodsmith machines are third-generation SBRs. Each has two retractable robotic probes that drill ahead of the shaft bottom to examine the ground and grout it before the cutting drum reaches it.

An additional control cabin on the surface allows more of the operation to be run remotely.

The service shaft is still less than halfway finished

As per the Anglo American's report, the Woodsmith service shaft at 904 meters, or 2,966 feet, out of a planned 1,600 meters, or 5,249 feet. That leaves 696 meters, or about 2,283 feet, to excavate.

The SBR is currently working through Sherwood Sandstone, a hard, water-bearing layer with high salinity. Anglo American said progress through this section is helping determine the project's overall schedule.

A second SBR was working on the production shaft, which reached 712 meters, or 2,336 feet, before sinking was paused in June 2024. That machine has remained suspended at that depth since the project was slowed.

The mine is beneath the North York Moors

Woodsmith sits just south of Whitby on England's northeast coast, beneath the North York Moors National Park. The site is above what Anglo American describes as the world's largest known deposit of polyhalite, a natural mineral fertilizer.

The company's plan is to extract the ore through two shafts roughly a mile deep and transport it through a 23-mile underground conveyor system to Teesside. The conveyor tunnel has reached 18.9 miles.

The SBR has limits on the rock it can cut

Herrenknecht's SBR is designed for shafts between 23 and 39 feet in diameter and depths of up to 5,249 feet. Its cutting system is rated for soft to medium-hard rock of up to 120 MPa, or roughly 17,400 psi. That includes salt, potash and sandstone.

For harder rock, Herrenknecht has developed a related Shaft Boring Cutterhead designed for rock of up to 250 MPa. The company demonstrated that machine at Bauma 2022. It weighs 450 metric tons and is designed to target shaft-sinking rates of 20 to 26 feet per day, according to International Mining.

Earlier projects established the technology

The SBR concept was previously used at BHP's Jansen potash mine in Saskatchewan. Two SBR machines cut shafts there to 3,297 feet and 3,199 feet by 2018. Herrenknecht describes the project as the first mine shafts sunk by mechanical excavation alone.

Second-generation machines were later used at the Nezhinsky potash project in Belarus, where two frozen shafts reached 2,461 feet and 2,287 feet.

The same contractor, Redpath Deilmann, is now operating the machines at Woodsmith.

China has also begun sinking a kilometer-deep vertical shaft using a 500-ton machine designed for harder rock than the SBR is intended to handle.

The project still has a long way to go

The Woodsmith service shaft remains well short of its planned depth, while the production shaft is still paused.

Anglo American said the rate of progress through the current sandstone section is helping determine the wider project schedule, which will feed into the final investment decision it is preparing for from 2028.