Observing an open-pit mine: a reference design

01What a mine needs to see

A mine observing site exists to keep people safe in the pit and to show neighbours and regulators that the mine stays within its limits. Both depend on knowing what the ground and the air are doing, continuously and in a form others can check.

Slopes come first. Mine safety rules in one national jurisdiction require ground conditions to be examined before work starts, after blasting, and as conditions warrant during the shift¹. Highwalls and banks next to travelways must be examined weekly, or more often if ground conditions change¹.

Instruments do not replace those examinations, but they fill the hours between them. Satellite positioning monuments on the benches track small movements of the wall, so a slow creep is seen as a trend long before it shows as a crack.

Blasting reaches beyond the pit. Surface mining rules set limits on ground vibration and air overpressure at nearby homes and public buildings, and require monitoring to show the limits are met².

The mine's wider footprint matters too. An industry standard for tailings facilities asks operators to apply good practice in design, operation, monitoring and closure to prevent catastrophic failure³. Dust is the other everyday concern, since air pollution is recognised internationally as a risk to heart and lung health⁴.

02Siting for the rock and the rules

Slope monuments go where movement would matter most: on benches above working areas and haul roads, anchored deep enough that they move with the rock mass rather than with loose surface material. Their spacing follows the geology and the mine plan, and it changes as the pit grows.

The blast seismograph is sited by the rules as much as by the rock. The regulator may specify where vibration and air overpressure are measured, and vibration is recorded as particle velocity in three perpendicular directions².

Air overpressure instruments must respond evenly up to a high frequency, and the rule sets the lower frequency limit of the measuring system for each overpressure limit². Choosing the instrument is therefore part of meeting the limit, not a detail left to purchasing.

Dust and blasting are hard on everything left in the pit. Equipment near the blast is placed behind cover or moved before firing, and antennas and solar panels are inspected after each blast, because a dusty panel or a shifted mast is an outage waiting to happen.

03One network down into the pit

The monuments, the seismograph and the fleet share one private mobile network. Mobile standards describe such non-public networks and note that they let an owner restrict access, prioritise traffic and keep some network functions on its own premises⁵.

A pit is a hard place for radio. Walls block the line of sight to the floor, haul trucks move through shadows, and the shape of the pit changes month by month. The simulator shows how frequency, power and mast height set the radius a single cell can serve.

Because the pit deepens, coverage is planned against the mine plan, not only today's surface. Extra radios on the benches or a second mast are added as the floor drops, before the shadow reaches the people working there.

04From sensor to decision

Positions from the monuments flow to the edge module on the rim, where movement is computed against a stable reference and compared with alert thresholds set by the mine's geotechnical engineers. Precise positioning uses open correction formats published for real-time satellite positioning⁶.

Seismograph records flow the same way, in an open time-series format that also carries the recording system's state of health⁷. A blast that exceeds its planned level can be reviewed within minutes, while the shot crew still remembers the details.

Decisions that protect people are made on site: clearing an area below a moving wall, or holding the next blast. Summaries and full records go on to the mine's planners, its regulator and, where it chooses, its neighbours, through an open interface for sensor observations⁸.

05What travels with each record

A vibration level without its context cannot settle a complaint or satisfy a regulator. Surface mining rules require each blast record to include the location, date and time of the blast, and any required seismograph and air overpressure records⁹.

Those seismograph records must name the type of instrument, its sensitivity and calibration, its exact location, the person who analysed the record, and the level recorded⁹. Records of all blasts must be kept for at least three years and made available on request⁹.

The reference design applies the same discipline to every value, not only to blasts. A slope movement, a dust reading and a vibration peak all leave the site with their time, place, instrument, method and quality flags attached.

06When the links fail

Mines are often far from public networks, and a single backhaul link joins the site to the outside. The reference design treats that link as something that will fail and plans for it.

When the link out is lost, the private network, the edge module and the local alerts keep running, and records are stored with their original times until the link returns. Slope alarms reach the people in the pit regardless.

When an instrument fails, its gap is recorded with a reason. A missing seismograph record is reported as missing, never estimated, because the record exists to show what actually happened.