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Public Health Service

Centers for Disease Control and Prevention

National Institute for Occupational Safety and Health

Analysis of Retreat Mining Pillar Stability (ARMPS):

Version 4.0 for Windows

Objective

To help prevent squeezes, collapses, and other pillar failures

through better pillar design, thereby enhancing safety for underground

mine workers.

Background

Proper pillar design is essential for safe pillar recovery operations.

Between 1989 and 1996, 25% of all roof and rib fatalities in the United

States occurred on pillar recovery sections. The Analysis of Retreat

Mining Pillar Stability (ARMPS) computer program was developed in

1995 and has been widely accepted by the mining community. A

Windows version of ARMPS is now available. It features simplified

data input, graphics, and an expanded online "HELP" facility.

How It Works

The ARMPS program estimates the loads applied to, and the loadbearing capacities of, coal pillars used in retreat mining. It then

calculates a stability factor (SF). ARMPS can model the significant

features of most retreat mining layouts, including angled crosscuts,

varied spacings between entries, barrier pillars between the active section

and old (side) gobs, and slab cuts in the barriers on retreat (figure 1).

It also features a pillar strength formula that considers the greater

strength of rectangular pillars. The program may be used to evaluate

bleeder designs as well as active workings.

A database of 140 pillar retreat case histories was collected across

the United States to verify the program. It was found that satisfactory

conditions were very rare when the ARMPS SF was

less than 0.75. Conversely, very few unsatisfactory designs were found

where the ARMPS SF was greater than 1.5 (figure 2). Preliminary

analyses also indicate that pillar failures may be more likely under

sandstone roof and that the ARMPS SF may be less meaningful when

the depth of cover exceeds 230 m (750 ft).

ARMPS is well suited for initial feasibility studies where no

previous experience is available. Operators may begin with an SF near

1.5 and then adjust as they observe pillar performance. In an operating

mine, ARMPS can be calibrated using site-specific experience. ARMPS

may also help in optimizing panel designs by identifying pillars that might

be needlessly oversized. The "HELP" text included with version 4.0 of

the program contains many tips on selecting the proper input parameters

when using ARMPS.

For More Information

To obtain a single copy of the ARMPS computer program, version

4.0 for Windows, send three double-sided, high-density diskettes to:

Christopher Mark, Ph.D., NIOSH Pittsburgh Research Center,

Cochrans Mill Rd., P.O. Box 18070, Pittsburgh, PA 15236-0070.

Information Circular (IC) 9446, "Proceedings: New Technology for

Ground Control in Retreat Mining," contains papers presented at

technology transfer seminars sponsored by NIOSH dur-ing 1997. The

papers describe several new, highly practical technologies developed by

the NIOSH Pittsburgh and Spokane Research Centers to improve safety

during pillar retreat operations, including ARMPS. Two central issues

are addressed: pillar design and mobile roof supports (figure 3). To

obtain a free copy of

IC 9446, contact Diane Felice, NIOSH Pittsburgh Research Cen-ter,

Cochrans Mill Rd., P.O. Box 18070, Pittsburgh, PA 15236-0070,

phone: (412) 892-4411, fax: (412) 892-6877, e-mail: def9@cdc.gov
Figure 1.—Section layout parameters used in ARMPS.

Figure 2.—ARMPS database.

Figure 3.—Full pillar extraction using mobile roof supports.

Mention of any company name or product does not constitute endorsement by the National Institute for Occupational Safety and Health.

To receive additional information about mining issues or other

occupational safety and health problems, call 1-800-35-NIOSH

(1-800-356-4674), or visit the NIOSH Home Page on the World

Wide Web at http://www.cdc.gov/

niosh/homepage.html

As of October 1996, the safety and health research functions of

the former U.S. Bureau of Mines are located in the National

Institute for Occupational Safety and Health (NIOSH).