Mine inspection: flying first into the voids people must not enter

A mine is a living structure whose shape changes with every blast. Underground: rockfall and slabbing from the back and walls, degrading ground support (rock bolts, mesh, shotcrete), and overbreak where a void collapses beyond its design. In open pits: rockfall and slope failure on high walls. And the hazard with the greatest potential for disaster beyond the mine itself: failure of a tailings storage facility.

The 2019 tailings dam failure at Brumadinho in Brazil killed more than 250 people. In its wake the Global Industry Standard on Tailings Management (GISTM) was published in 2020, sharply raising the importance of routine monitoring and records.

Underground, safety staff walk the drifts at set intervals, inspect visually, bar down loose rock (with a scaling bar or a scaling machine) and check ground support. Stopes that people cannot enter have been measured with a cavity monitoring system (CMS) — a laser scanner pushed in on a boom from the brow. Open pits rely on surveying and visual checks; tailings facilities on piezometers, displacement monitoring and patrols.

In mining, time and danger are tightly linked. After a blast nobody may enter until the fumes clear; the next task waits until the void is measured; and the more people hurry, the closer they get to unsafe ground. The challenge is to know quickly *and* safely.

Most underground drones localise themselves with LiDAR SLAM while mapping their surroundings. They fly autonomously beyond GPS and radio range, measure, and return. On the surface, photogrammetry covers open pits and tailings facilities quickly and widely.

The basic underground pattern is to fly autonomously from the brow out of line of sight, and always return within a set time. When the radio link drops, the aircraft navigates home on the map it built. For voids it may not come back from, plan on possibly losing the aircraft — far better than losing a person.

Underground is one of the harshest environments for drones: no GNSS and no radio, total darkness, tight spaces and dust. After blasting there are toxic fumes and oxygen deficiency, and coal mines carry the constant threat of explosive methane atmospheres.

• GNSS-denied: choose aircraft that localise with LiDAR SLAM and return autonomously when the link drops. GNSS-denied
• Darkness: combine onboard lighting with LiDAR, which does not need light. Darkness
• Confined spaces: check drift cross-sections and shaft diameters, and choose collision-tolerant aircraft. Confined spaces
• Dust & smoke: right after a blast, dust blinds both LiDAR and cameras. Wait for ventilation to clear it. Dust & smoke
• Oxygen deficiency & toxic gas: a drone can look before the post-blast fumes have cleared, and some carry gas detectors. Oxygen deficiency & toxic gas
• Explosive atmospheres: where methane is present, as in coal mines, some areas allow only certified explosion-protected equipment. Assume ordinary drones are not allowed. Explosive atmospheres

In mining, point clouds matter more than photos. Overlay a stope scan on its design and overbreak and underbreak are obvious; overlay a drift scan on last month’s and convergence becomes visible. But whether to add support or allow people back in is decided by geotechnical engineers and the people responsible for safety.

In Japan, mine safety is governed by the Mine Safety Act, which requires mine operators to identify hazards and take measures, under the supervision of METI’s regional industrial safety and inspection departments. Many operating mines in Japan are reported to be open-pit operations such as limestone quarries, so drones are mainly used for surveying and wall monitoring.

For the flight itself, open pits and tailings facilities are outdoors and subject to aviation law. Flights in enclosed underground spaces may be treated differently, so confirm in advance. In both cases, write drone flights into the mine’s safety rules and permit-to-work system.

Abroad, the US Mine Safety and Health Administration (MSHA) sets requirements such as permissibility for equipment used underground, while in Australia both state mining regulators and the aviation regulator CASA apply. For tailings, GISTM is spreading as the international benchmark. Compare national flight rules in world regulations.

• Barring down loose rock: scaling is work for people and scaling machines. Drones only find where it is needed.
• Conditions inside the rock: rock stress and internal fractures cannot be read from surface shape. Instruments and ground investigation are needed.
• Underground areas with explosive atmospheres: where methane is present, only certified equipment may be used — not ordinary drones.
• Dense dust right after a blast: LiDAR and cameras are blinded. Wait for ventilation.
• Long flights: battery endurance is short, and a large mine cannot be covered in one flight.
• Decisions and accountability: adding support, allowing entry and judging tailings safety stay with people.

While the post-blast fumes clear, a drone flies into the void, maps it and returns. By the time people go back underground, the overbreak, a revised blast design and the places needing extra support are already on screen. Drifts are scanned on the same route every week, and convergence is tracked millimetre by millimetre.

Tailings facilities are watched daily by satellites, ground instruments and drones, and the accumulated record of “no anomaly” becomes the explanation owed to people living downstream. That is our editorial view — and we expect scaling and installing support will still be done by people and machines.