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| Retreat mining pillar line roof fall fatality site, Mingo County, West Virginia |
Description of Problem
When coal is first mined, large pillars of coal are left to support the rock between the mine and the surface. When these pillars are later recovered, the ground collapses. Nationally, coal pillar recovery accounts for just 10% of coal mined underground, but it is associated with more than 30% of mine roof fall fatalities.
Research and Development Activities
NIOSH has been conducting research to reduce the ground fall hazard during coal pillar recovery since the early 1990s. Significant research products include:
- The Analysis of Retreat Mining Pillar Stability (ARMPS) computer program (1994-1997)
- Advocacy of the use of mobile roof supports for temporary roof support (1994-present)
- Guidelines for coal pillar and panel design to prevent massive pillar collapses (1993-1997)
- Guidelines for panel and barrier pillars for pillar recovery under deep cover (2002)
- Guidelines for sizing the final stump to prevent unplanned roof collapse (2001)
- Guidelines for cut sequencing and roof bolting, and identification of other risk factors for pillar recovery, such as old works, multiple-seam mining, and wide roof spans (2002)
R&D Outputs and Transfer Activities
NIOSH has transferred these results through:
- Distribution of more than 1,000 copies of the ARMPS computer program
- A NIOSH Information Circular entitled "New Technology for Ground Control in Retreat Mining." This publication was used in conjunction with an open industry briefing held throughout the U.S. coalfields and attended by more than 300
- Industry short courses for Arch Coal, Massey Energy, and Peabody Energy (100 attendees)
- Joint MSHA-NIOSH Preventative Roof-Rib Outreach Program (PROP) seminars held in MSHA districts and attended by at least 500
- Numerous conference papers and presentations
Description of Intermediate Outcome
Following a series of meetings with MSHA District 4, the West Virginia Office of Miners' Safety, Health, and Training, and the West Virginia Board of Coal Mine Health and Safety, many of the guidelines included in the checklist were incorporated into the roof control plans of nearly 100 mines in southern West Virginia. Others have been implemented in the mining plans of several large mining companies (for example, Massey Energy does not extract the pushout, or remnant pillar). In the 3 years since the guidelines were implemented in District 4, there has been just one fatality associated with coal pillar recovery. This compares with an average of one per year during the prior 5 years. The research has also contributed to significant changes in the way pillar recovery is practiced throughout the United States. Today, more than one-half of all pillars are recovered using mobile roof supports. Fewer and fewer roof control plans allow extraction of the final stump. Mine operators, MSHA, and state regulators are more aware of the risk factors and often specify extra support in pillar recovery sections. Although it is still early to be certain, there is every reason to believe that the national fatality rate for coal pillar recovery will decrease in the future.