One Hundred Years of Federal Mining Safety and Health Research

Worldwide experience has shown that the CMRR is a reliable, meaningful, and repeatable
measure of mine roof quality.
NIOSH has developed a wide variety of ground control design tools based on the CMRR. These
tools address a broad range of issues, including longwall pillar design, roof support selection,
feasibility studies, extended-cut evaluation, and others. As a result, the CMRR is becoming the
accepted standard for geotechnical characterization of mine roof and is often referred to in the
technical literature. The CMRR has also become truly international, involved in mine designs
and research projects funded by the Safety in Mines Research Advisory Committee (South
Africa), the Canada Centre for Mineral and Energy Technology, and the Australian Coal
Association Research Program.
6.2.10 Guidelines for Coal Pillar Recovery
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 percent of coal mined underground, but it is associated with more
than 30 percent of mine roof fall fatalities.
NIOSH has conducted 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)
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 the 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.
6.2.11 Support Technology Optimization Program (STOP) Design Software
New mine roof support products with distinct performance characteristics are developed each
year. The performance characteristics and limitations of these support systems are evaluated
through full-scale testing in the NIOSH mine roof simulator at the Pittsburgh Research
Laboratory. This information provides the basis for which these support systems are considered
for specific applications by mining companies and approved for use by MSHA.
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