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An analysis of violent failure in U.S. coal mines - case studies.

Proceedings: Mechanics and Mitigation of Violent Failure in Coal and Hard-Rock Mines. Special Publication: 01-95, Washington, DC: U.S. Bureau of Mines, 1995 May; :5-25
A U.S. Bureau of Mines (USBM) researcher analyzed the causes of violent failure using data from 12 U.S. coal mines as part of the USBM's mission to improve mine safety. It was shown that coal bumps are influenced by stress, stiffness, and yield ability of surrounding rocks, and the dynamic effects associated with failure of surrounding strata. In all bump-prone mines studied, calculated seam stresses exceeded unstable strength levels by at least 20 to 30 pet. In addition, bumps occurred in parts of the mines where there had been rapid stress changes over a short period of time and/or distance. The dynamic effects associated with the failure of surrounding strata triggered bumps in these marginally stable seam structures. While it was not possible to evaluate the influence of mine stiffness directly, it was shown that coal bumps generally occurred in mines with uniaxial compressive strength and Young's modulus ratios (roof to coal) exceeding 3 to 5. In addition, bump-prone coal exhibited the potential for storing high horizontal stresses. Yielding of the immediate roof and floor reduced horizontal stresses and enhanced gradual failure of coal. A method is proposed to assess coal bumps in which stress analyses, in situ strength data, stiffness and strength ratios of roof to coal, and expected wave magnitude resulting from strata failure and mining experience are incorporated.
Mining-industry; Coal-mining; Rock-falls; Rock-bursts; Rock-mechanics; Underground-mining; Control-technology; Geology; Geophysics; Engineering-controls; Ground-control; Ground-stability
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Book or book chapter
Maleki-H; Wopat-PF; Repsher-RC; Tuchman-RJ
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NIOSH Division
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Proceedings: Mechanics and Mitigation of Violent Failure in Coal and Hard-Rock Mines