Mining Project: Identification of Areas at Risk for Coal Bursts in Deep Cover Room and Pillar Mines
To develop enhanced guidelines for identifying "red zones," defined as areas within which the risk of coal bursts is significantly elevated. The guidelines will be based on an improved understanding of the geologic, stress, and mining factors that contribute to the burst risk.
|Keywords||ground control, prevention through design, underground mining|
After the Crandall Canyon mine disaster, NIOSH was asked to prepare a research report on the safety of deep cover room-and-pillar retreat underground coal mines. That report identified coal bursts as one of the major hazards faced by miners in these operations, and found that a key step in burst control is to identify those "red zone" areas that might be prone to bursts. Continued research to develop enhanced guidelines for burst control was one of the NIOSH report's recommendations.
This project's purpose was to develop enhanced guidelines for identifying "red zones," defined as areas within which the risk of coal bursts is significantly elevated. The guidelines were based on an improved understanding of the geologic, stress, and mining factors that contribute to the burst risk, and they will be included in the MSHA-approved roof control plans of mines with depths exceeding 1,000 ft. The project directly addressed Strategic Goal #6 of the Mining Program Strategic Goals for Intramural Research: Eliminate ground failure fatalities and injuries in the mining industry.
This project focused on defining the geologic and stress criteria associated with an elevated risk of coal bursts, considering both U.S. and international experience. Specific tasks included:
- A thorough comparison of the geology (including stratigraphy and rock mechanics properties) and mining stresses (including topographic and multiple seam stresses) in bump-prone areas and non-bump-prone areas of the U.S. Visits were made to mining operations in the burst-prone coalfields of Central Appalachia and the West to obtain the data.
- Visits to Europe and to Alabama were made to collect geologic and stress data from these coalfields (data from deep cover mines in Australia is already available). Rules of thumb used in the European coalfields to identify high risk zones were also documented.
- Statistical methods, empirical techniques, and (as appropriate) numerical models were employed to quantify the characteristics of burst-prone ground that differentiate it from burst-free ground.
- Based on the spatial variability of the critical factors that define burst-prone ground, guidelines were developed for the spacing, depth, and interpretation of underground test holes, the application of rock mechanics tests on underground core samples, and record-keeping of observations relating to the likelihood of coal bursts. Once a burst risk rating system was developed, it was implemented into a mine mapping software platform by means of an external contract.