Over the past two decades, there has been a tremendous growth in the amount of coal produced in the United States by the longwall-mining method. During the early-to-mid 1970s, approximately 120 longwall faces contributed less than 5% of the nations's underground coal output; currently, half as many faces contribute nearly 50% of the nation's underground coal output. All this has taken place during a time period when the total underground production grew less than 20%. In addition to the introduction of new technology, new management, operational, and engineering practices have contributed to this explosive growth. Specifically, changing out at the face, lengthened longwall faces, deeper panels, and longer shifts have increased system availability, thereby resulting in these remarkable production gains. However, longer faces and shifts create a concern for the health and safety of face personnel because of increased exposure to workplace hazards and fatigue. This paper examines the impact of increased face lengths, varying mining heights, and increased shift lengths on the accident and injury experience of U.S. longwall mines. Although no statistical significance was established between the three trends and the nonfatal days lost incidence rate, the no days lost incidence rate, and the severity measure - due to limited or nonexistent data, or widely varying incidence rates - a trend was established between the nonfatal days lost incidence rate and shift length. Specifically, for every hour of shift length above eight hours, the nonfatal days lost incident-rate ratio was 1.185, implying that a 18.5% increase in the number of nonfatal days lost incidents is predicted when a shift is extended one hour in the range from eight to nine, or nine to ten hours.
ASJC Scopus subject areas
- Geotechnical Engineering and Engineering Geology