Ground falls in U.S. underground mines (coal and nonmetal) caused more than 50,000 deaths or about half of all mining fatalities during the 20th century. Over the past 10 years, there have been significant improvements in ground control safety. Figure 1 shows that the roof fall fatality rate in U.S. underground mines has averaged 0.001 per 200,000 during the past 3 years, down 69% from its average during 1980-1995. In addition, the rock fall injury rate has fallen in each of the last 4 years to a level about 25% below its former plateau.

NIOSH has contributed to this historic improvement through its customer-focused, goal-oriented ground control research program. Important NIOSH 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 make pillar recovery much safer.
• Guidelines for designing deep-cover mines to prevent coal bumps (violent failures of highly stressed coal). These guidelines have contributed to 7 consecutive years with no fatalities due to coal bumps.
• New 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 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 provide more stable mining environments.

More details on each of these accomplishments and impacts can be found in the "Intermediate Outcome" write-ups.

An essential part of the success of the NIOSH ground control program has been an effective technology transfer effort. The centerpiece has been the suite of ground control software packages that has been developed from the research. There are now eight NIOSH programs. These address nearly every aspect of ground control planning for coal mines. This includes geologic characterization, mine layout, pillar design, and support selection. These products are used throughout the mining community. They are among the most requested and downloaded products from the NIOSH Mining Website. Other technology transfer efforts include:

• Hands-on ground control software computer training workshops held in six U.S. coalfield locations. These were attended by nearly 300 mine planners.
• Annual safety seminars for underground stone mines. These are attended by more than 150 professionals in the stone industry each year.
• Open industry briefings on coal mine roof support. These were held in eight U.S. coalfield locations and reached 750 mining industry personnel.
• Ground control short courses conducted for Massey Energy and Peabody Energy.
• Ground control training provided in eight sessions for all 400 coal mine inspectors from the Mine Safety and Health Administration (MSHA) at the agency’s request.
• An annual response to an average of 200 technical requests and 40 visits at coal and nonmetal mine sites.

Another important component of our technology transfer program is the MSHA-NIOSH partnership in the Preventative Roof-Rib Outreach Program (PROP). PROP has sponsored nearly a dozen full-day or half-day seminars in nearly every MSHA coal mining district. These seminars are tailored for the specific needs of each district. Attendance at these seminars is usually 50 to 100. NIOSH provides about half of the speakers. In addition, PROP has sponsored 2-day seminars at MSHA’s National Mine Health and Safety Academy in each of the last 5 years. These were attended by about 150 miners each year.

NIOSH has developed a particularly close relationship with the MSHA Technical Support group at Bruceton, PA. Our collaborations with them facilitate quick results and implementation by the MSHA districts. Partnerships with mine roof support manufacturers have greatly enhanced the effectiveness of the NIOSH mine roof simulator (MRS). The impartiality of safety testing in the MRS is accepted across the mining community. Thus, NIOSH has been able to help in the rapid commercialization of more than 40 new roof support technologies over the past 5 years.

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.

A new initiative is aimed at developing a set of engineering design guidelines to minimize unplanned roof failures in underground stone mines. Another software package will help coal mine planners minimize hazards when using multiple-seam mining techniques. Recent advances have coupled microseismic monitoring of rock failure events to measurements of mine roof movements. This has resulted in a sensor-based roof fall warning technology for identifying potentially hazardous areas. Standing support improvements and a better understanding of rock mass behaviors will provide opportunities for reducing the threat posed by massive roof falls to underground workers.

Figure 1. Ground fall fatality rate in underground mines (3-year moving average).

Rock burst control for hard-rock mines has been part of the ground control research program for more than 30 years. Great progress has been made in alleviating the rock burst problem in U.S. deep-metal mines. Seismic monitoring, in conjunction with rock mass behavior measurements and numerical modeling, has led to the development of safer mining methods and layouts.

NIOSH has also provided solutions to reduce ground fall hazards in Nevada underground mines. From 1999 to 2005, the mine design curves and applicable nomograms resulting from this research were transferred to the mining industry through 11 technical papers and 9 presentations.