Mining Project: Coal Mine Safety Applications of Seismic Monitoring
To implement in-mine seismic monitoring techniques in coal mines to evaluate and demonstrate potential mine safety benefits of this technology. These benefits include use of the resulting data for improved ground control hazard management, rock mass modeling, and mine and support design practices in deep coal environments.
|Keywords||ground control, mining, underground mining|
This project has four research aims, as follows:
- Implement a seismic monitoring system at cooperating mines to evaluate sensor density and distribution requirements for resolving event locations on different structurally important features.
- Characterize seismic response associated with key deformation processes (caving, bridging, pillar deformation, etc.) in the instrumented mines.
- Quantify observed seismic response with stress and deformation predicted by numerical models.
- Use seismic data to evaluate mine design performance and critical design assumptions.
Sudden, brittle failure of highly stressed ground around deep underground coal mines can drive ground falls, coal bursts, bumps, and even sudden collapse of large mine areas. The collapse at Crandall Canyon Mine in 2007 is a notable example. In many instances, failures occur well away from the perimeter of the mine opening and can involve geologic structures that may not be known to miners. Loading of these structures may cause cracking, failure, or caving, which can generate seismic signals that can be monitored, measured, and interpreted. The interpretation of these data combined with other tools (e.g., core testing), can be used to help identify potentially dangerous instabilities. This approach is routinely employed in deep metal mines in countries including South Africa, Canada, Australia, and the United States. It is also employed in some deep European longwall coal mines.
Despite the successful use of seismic monitoring in mines, technical obstacles have limited their application in deep coal mines in the United States to a small handful of experimental installations. Research under this project seeks to overcome these obstacles and bring this hazard identification tool into the mainstream of coal mine safety systems. This objective was one of several recommendations made by NIOSH in a report to Congress in response to the Crandall Canyon coal mine collapse.
This project research has adapted microseismic monitoring technology to conditions encountered in a collaborating fast-moving deep longwall coal mine. The monitoring system includes both surface stations, installed in rugged mountainous terrain with radio link communications, and underground stations monitored through fiber optic links. The system has successfully collected a wealth of data including seismic data sequences occurring in conjunction with three damaging rockbursts. Analyses of these data sets indicate the ability to track large-scale ground movements in ways currently unattainable by other methods.
The data generated by this research can and are being used to evaluate (1) fundamental assumptions made in deep longwall coal mine design; (2) the ability of numerical models to characterize and project rock mass response in these environments; and (3) the best approaches to identify and assess ground failure risks.