One Hundred Years of Federal Mining Safety and Health Research

6.2.8 Ground Control
Ground falls in U.S. underground mines caused more than 50,000 deaths or about half of all
mining fatalities during the 20th century. Over the past 10 years, significant strides in ground
control safety have been made. Important NIOSH ground control research products that have
been successfully transferred to and implemented by the mining community during the past
decade include:
• The Support Technology Optimization Program (STOP) and Analysis of Longwall Pillar
Stability (ALPS) programs, which together have contributed to a virtual elimination of
tailgate blockages.
• The underground stone ground control safety initiative. This initiative has increased
awareness about rock fall hazards and helped to greatly reduce fatalities in stone mines.
• Guidelines for coal pillar recovery and widespread use of mobile roof supports. These
have helped to make pillar recovery much safer.
• New types of standing roof supports. These have helped reduce the number of roof falls
and the number of injuries to miners while installing roof support.
• A research and educational campaign aimed at increasing awareness about rock fall
injuries and the use of surface controls in coal mines. This has helped to reduce rock fall
injury rates.
• Mine design technologies such as the Coal Mine Roof Rating (CMRR) and Analysis of
Horizontal Stress in Mines (AHSM), and guidelines for preventing massive pillar
collapses. These have helped to provide more stable mining environments.
International collaboration is another measure of the caliber and impact of the NIOSH ground
control program. During the past 8 years, six major funded research projects in Australia,
Canada, the European Union, and the Republic of South Africa were based on NIOSH research.
These focused on the STOP, ALPS, Analysis of Retreat Mining Pillar Stability (ARMPS), and
CMRR software packages.
6.2.9 Coal Mine Roof Rating System
One reason that roof falls have been so difficult to eradicate is that the structural integrity of a
coal mine’s roof is greatly affected by natural geological weaknesses, including bedding planes,
fractures, and small faults. The engineering properties of rock cannot be quantified solely by lab
tests, because the strength of a small specimen is representative only of that sample, not taking
into account the imperfections caused by local discontinuities.
NIOSH developed the Coal Mine Roof Rating (CMRR) system in the 1990s to fill the gap
between geologic characterization and engineering design. This system combines many years of
geologic studies in underground coal mines with worldwide experience with rock mass
classification systems. New CMRR procedures for the borehole drill core, together with a
software package, were developed in 2000 and made it possible to routinely collect CMRR data
during geologic exploration. NIOSH has responded to requests for assistance in using the
CMRR from many mining companies and geologic consultants, both domestically and abroad.
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