Mining Project: Advancement of Refuge Alternatives for Underground Coal Mines

Research Summary

Although refuge alternatives (RAs) have been required in underground mines for nearly 10 years, knowledge gaps remain in several areas. With respect to heat buildup within RAs, concerns remain related to the appropriate heat input to represent miners in an RA, the appropriate heat stress metric to protect miners in a refuge situation, occupancy derating of RAs for warmer mines, conversion of laboratory heat and humidity test results to results that would be representative of in-mine RA use, heat mitigation strategies for RAs, and the effect of fires and explosions on mine temperatures near an RA. Further, in spite of numerous potential advantages of built-in-place (BIP) RAs, their use is not widespread. Guidance on BIP RA air supplies, ventilation systems, and stopping/door system designs are needed to ensure the widespread use of BIP RAs. In addition, although Mine Safety and Health Administration (MSHA) regulations require communications between surface personnel and underground miners inside an RA and an independent additional communications system within the RA, little work has been done to examine communications from within deployed RAs to the surface. Furthermore, most RA manufacturers do not have expertise in radio communications and leave it to the mine operator to integrate the mine communications system with the RA.

The NIOSH Mining Program is addressing the above concerns using a combination of contracts and in-house research. Contracts are addressing the appropriate heat input, heat stress metric, and procedure for adjusting laboratory data to account for mine thermal behavior and post-disaster temperatures. In-house research is developing standard simulated miners for use during RA heat and humidity testing, and to evaluate heat mitigation strategies for RAs. The Mining Program is also performing in-house research to examine blast response of BIP RA stopping/door systems and  determine a reliable method to verify wireless communications from within an RA without having to deploy or enter the RA.

To address BIP RA concerns, the Mining Program is primarily using in-house project research. Research on air delivery and ventilation systems is being performed using NIOSH's newly constructed BIP RA test facility in its Experimental Mine in Bruceton, PA. NIOSH is using a newly developed relief valve test stand to test and develop relief valves for BIP RAs, and finite element analysis software to aid in the design of relief valves and door/stopping systems for BIP RAs. Ultimately, a test apparatus is planned to pressure-test door/stopping systems to 15 psi and to determine their ability to withstand shrapnel resulting from a mine explosion.

This project has research aims related to heat stress in RAs, RA air delivery systems, facilitation of broad use of BIP RAs, and RA communications and tracking.

The research aims related to heat stress include: (1) to identify the appropriate heat input to represent miners that enter an RA; (2) to determine the RA air temperature and relative humidity that cause a body core temperature rise for miners that enter an RA; (3) to develop a standard heat input device for RA heat and humidity testing; (4) to develop a method to use laboratory RA heat and humidity test results to calculate in-mine RA heat and humidity; (5) to examine heat buildup inside BIP RAs; (6) to evaluate heat mitigation strategies for RAs; and (7) to determine the effect of fires and explosions on the mine temperatures near an RA post-disaster.

The research aims related to RA air delivery systems and facilitation of broad use of BIP RAs include: (1) to develop guidelines for the use of boreholes, protected compressed airlines, and cryogenic air supplies for use in mobile and BIP RAs; (2) to develop guidelines for BIP RA ventilation system layout, relief valve design, and contamination ingress prevention strategies within BIP RAs; and (3) to develop practical BIP RA stopping/door systems that can withstand a 15-psi overpressure.

With respect to RA communications, the research aim is to develop reliable communications methods for RAs that provide interoperability with a mine’s primary communications system that can notify surface operations that an RA has been deployed.

Results from this project research will be published in numerous journal articles distributed to industry and policy makers interested in heat stress in RAs, RA air delivery systems, RA communications, and the use of BIP RAs.

Related Video: NIOSH Research on Refuge Alternatives for Underground Coal Mines