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Mining Project: Assessing Elevated Stress Due to Full Extraction Mining

Principal Investigator
  • Ted Klemetti, NIOSH, 412-386-5240
Start Date10/1/2015
Objective

To develop engineering-based stress analysis procedures for improved assessment of stress-related hazards due to full extraction mining.

Topic Areas

Research Summary

This project has five research aims, as follows:

  1. Determine the effect of gob development and resulting stress redistribution due to full extraction operations through field monitoring.
  2. Develop numerical models that can simulate stress redistribution and associated pillar and ground response resulting from full extraction mining, and conduct parametric studies to examine controlling factors.
  3. Determine the critical overburden and floor strength and stiffness relative to elevated stresses that drive dynamic failure(s) that leads to burst conditions.
  4. Develop a standardized procedure to predict the elevated stresses due to full extraction mining.
  5. Develop a rating scale for burst likelihood for coals in the US.

Dynamic rock and coal failures are a significant hazard during full extraction mining. These events are known as coal “bumps” or “bursts.” According to Mine Safety and Health Administration (MSHA) accident data, there were approximately 380 coal burst events reported from 1983 to 2013. Of those, 20 resulted in fatalities with 33% in longwall mines. There were two additional fatalities in a single event in 2014 during room and pillar retreat mining. The two most recent coal burst events that resulted in fatalities occurred in room and pillar retreat mining operations with distinct multi-seam interactions specifically at the accident sites.

Numerous research endeavors during the past 25 years have identified and implemented improved mine design and operational practices that have successfully reduced the rate of occurrence of burst events to the point where catastrophic events today are very rare. Nonetheless, the potential for such events and the ongoing challenge of prevention mandate that continued research be conducted to fully eliminate them.

This project’s research will use the best available geological data and improved identification of potential areas of elevated stress associated with full extraction coal mining to provide the most accurate risk assessment relative to full extraction mining, given current geotechnical practices in the US coal mining industry. Providing an improved picture of the stress regime will also enable future enhancements in geological characterization, which will be developed through other efforts to further refine the identification of conditions and mechanisms that control bursts and lead to further risk assessment enhancements. Ultimately these two research agendas—stress assessment and geological characterization—will combine to provide the best opportunity for developing prevention measures and avoidance forecasting designed to eliminate bump catastrophes. This project will primarily benefit research efforts related to coal bursts, but is also applicable to all ground control issues and may help to reduce other safety hazards in underground coal mining.


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