The Definition of Ground Control (Mining)

Definition of Ground Control (Mining)

Ground control is the set of methods mines use to prevent falls of roof, face and ribs underground, and failures of highwalls, benches and slopes at surface mines.

Rock and coal are not uniform. Joints, faults, weak layers, water and stress changes from mining can all cause ground to loosen and fall. Falls of ground have historically been a leading cause of mining fatalities. Even small pieces of rock falling from the roof or a rib are a deadly struck-by hazard. Large failures can bury equipment and crews or trap miners behind a collapse.

Ground control applies in underground coal mines, underground metal and nonmetal mines, surface pits and quarries. It involves mine engineers who design support plans, roof bolter operators who install support, foremen and examiners who inspect conditions, and every miner who works under or near exposed ground. It is regulated by MSHA.

Key Elements of Ground Control

Underground Support

• Roof bolts: steel bolts anchored into the roof to bind rock layers together and hold them in place.
• Mesh and straps: wire mesh or steel straps held by bolts to catch small pieces of rock between bolts.
• Rib bolts: bolts installed in the sides of an entry to stop rib rolls and spalling.
• Standing supports: cribs, cans, posts and other supports set between the floor and roof, often used in wide areas, intersections and during pillar recovery.
• Temporary support: jacks or posts set to protect the person installing permanent support.

Surface Stability

• Highwall and slope design: angles and bench widths chosen to suit the rock and keep walls, banks and slopes stable.
• Benches and catch areas: flat steps that catch falling material before it reaches work areas below.
• Scaling: removing loose material with proper tools from a safe location, never from beneath the loose ground.

Examination and Monitoring

• Ground examinations: a competent person checks ground conditions before and during work and looks for cracks, loose rock, water and drummy roof.
• Monitoring: seismic monitoring and convergence measurements track ground movement over time and warn of developing problems.
• Barricades and postings: hazardous areas are barricaded and posted to create a keep-out zone until the hazard is fixed.

Regulations and Standards

MSHA Underground Coal: 30 CFR Part 75

• 30 CFR 75.202: the roof, face and ribs of areas where persons work or travel must be supported or otherwise controlled. Under 75.202(b), no person may work or travel under unsupported roof unless they are installing temporary support.
• 30 CFR 75.220: each mine must have a roof control plan suitable to the prevailing geological conditions and the mining system. The plan must be approved by the MSHA District Manager.
• 30 CFR 75.223: the roof control plan must be reviewed at least every six months.

MSHA Metal and Nonmetal: 30 CFR Parts 56 and 57

• 30 CFR 56.3130: surface mines must follow mining methods that keep walls, banks and slopes stable.
• 30 CFR 56.3200 and 57.3200: hazardous ground conditions must be taken down or supported before other work or travel is permitted in the area. Until the work is done, the area must be posted with a warning against entry, and a barrier must be installed when it is left unattended.
• 30 CFR 57.3360: underground mines must use ground support where ground conditions or mining experience in similar conditions show it is needed.
• 30 CFR 56.3401 and 57.3401: a competent person must examine ground conditions in areas where work is to be done.

Ground control also ties into the broader workplace examination requirements that apply to each working place.

Good Practices for Ground Control

• Never go under unsupported roof: treat the last row of bolts as a hard line. Only install temporary support beyond it.
• Follow the plan: install support exactly as the approved roof control plan requires, and stop to reassess when conditions change.
• Examine before work: have a competent person check ground at the start of each shift and after blasting, rain or freeze and thaw cycles.
• Scale from a safe spot: use bars of proper length or mechanical scalers, and stay out of the line of fire of falling rock.
• Barricade bad ground: post hazardous ground right away and barricade it if it is left unattended.
• Watch for warning signs: report cracks, popping, dribbling material, water and bolt plates taking load.
• Track the data: log ground falls and support failures, including non-injury falls, to find trends. Tools such as SafetyIQ's safety audit software can help record examinations and follow up on corrective actions.

Example of Ground Control (Mining)

An underground limestone mine noticed small pieces of rock dropping from the back near an intersection after a series of production blasts. A loader operator parked near the area during a break. A slab about the size of a car door fell where he had been standing a few minutes earlier. No one was hurt, but the fall showed the existing pattern of bolts was not enough for that part of the mine.

The mine barricaded and posted the intersection, scaled the loose ground from a safe position, and brought in a ground control consultant. The support standard was revised to add longer bolts and mesh at intersections. Examiners now use a written checklist at the start of each shift and after blasting. Parking under recently blasted ground is no longer allowed, and all ground falls are logged and reviewed monthly.

Frequently Asked Questions: Ground Control (Mining)

What is a roof control plan?

A roof control plan is a written plan for supporting the roof, face and ribs in an underground coal mine. Under 30 CFR 75.220, it must suit the mine's geological conditions and be approved by the MSHA District Manager. It must be reviewed at least every six months.

Can a miner ever go under unsupported roof?

In underground coal mines, 30 CFR 75.202(b) bars work or travel under unsupported roof except to install temporary support. Even then, the person must follow the approved plan and use the required temporary supports.

What is scaling in mining?

Scaling is the removal of loose rock from the roof, ribs, faces or highwalls before it can fall. It must be done with proper tools from a location where the person doing it is not exposed to the falling material.

Why are falls of ground so dangerous?

Falls happen with little or no warning and the material is heavy. Even a small rock falling a few feet can cause fatal injuries, and large falls can trap miners or crush equipment.