In August 2005, two eastern Kentucky coal miners died in a roof fall during retreat mining operations. They had just finished extracting one pillar block and were moving to the next one when the intersection they were standing in collapsed. Regrettably, this was not an isolated incident. Since the end of 2000, there have been 28 ground fall fatalities in U.S. coal mines. Of these, 10 occurred during pillar recovery operations. Although pillar recovery has been associated with about one-third of recent ground fall fatalities, it accounts for only about 10% of U.S. underground coal production. Statistically, a coal miner engaged in pillar recovery is several times more likely to be killed in a ground fall than a miner on an advancing section of a longwall. Pillar recovery is dangerous because it creates an inherently unstable situation. Once the pillars are extracted, the roof is expected to cave. Safe pillar recovery does not mean preventing roof collapse; it means ensuring that it occurs only after the miners have completed their work and have left the area. Fortunately, there are a number of proven techniques that can greatly reduce the hazards of pillar recovery. These include better mine planning, improved roof support, and safer work procedures. This article describes the most significant risk factors associated with pillar recovery and prescribes control techniques that, taken together, can reduce the overall risk to miners. The conclusions are based on extensive studies conducted by NIOSH and the Mine Safety and Health Administration that include detailed analysis of every fatal retreat mining incident since 1992 (25 incidents resulting in 30 fatalities). Risk reduction strategies for pillar recovery can be divided into three main groups: (1) global stability (preventing section-wide pillar failure), (2) local stability (preventing roof falls in the working area), and (3) work procedures and worker location (minimizing exposure to hazardous areas).
Mining-industry; Coal-mining; Underground-mining; Retreat-mining; Ground-control; Ground-stability; Hazards; Injuries; Safety-research; Rock-mechanics; Accidents; Rock-falls; Miners; Underground-miners; Coal-miners; Risk-factors; Demographic-characteristics; Geology; Training; Computer-software; Room-and-pillar-mining; Mining-equipment
NIOSH Pittsburgh Research Laboratory, P.O. Box 18070, Pittsburgh, PA 15236