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What has the Mining Program accomplished?

Intermediate Outcome (14 of 19) related to Preventing and Mitigating Mine Fires and Explosions

Protecting Coal Miners from Gob Explosions through Explosion-Resistant Mine Ventilation Seals (1993-2005)

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NIOSH researchers inspecting a mine seal before hydrostatic testing
NIOSH researchers inspecting a mine seal before hydrostatic testing

Description of Problem

Ventilation seals are used extensively in mining to safely isolate old workings and fire areas from the active sections of a mine to protect underground workers from explosions. Without reliable seal designs, miners' lives could be in jeopardy from the consequences of an underground explosion.

Research and Development Activities

The NIOSH Pittsburgh Research Laboratory (PRL), in partnership with national and international mine operators, seal manufacturers, and the Mine Safety and Health Administration (MSHA), has developed and evaluated numerous new and innovative seal designs. The main focus of the effort was to develop mine sealing technologies for use during mine emergencies, within unique geological conditions in the mine, and/or for generalized mine gob sealing.

All new seal designs were performance-tested in PRL's Lake Lynn Experimental Mine (LLEM) for strength characteristics against explosions and for air leakage resistance before and after an explosion. If the seal design met the requirements of the program as set forth at 30 CFR 75.335, MSHA then deemed the seal design acceptable for use in underground coal mines. Twenty-seven different seal designs have been developed and evaluated in the LLEM.

R&D Outputs and Transfer Activities

The results of this research have been distributed through reports to MSHA, publications, and workshops. NIOSH researchers have collaborated closely with manufacturers and mine operators to translate this research into practice. The seal designs that have been developed and proven in the LLEM have been deemed suitable by MSHA and are now being built and used daily in the United States and abroad.

Description of Intermediate Outcome

More than 35,000 seals based on designs tested in the LLEM have been installed in commercial coal mines in recent years. For example, Strata Mine Products has installed more than 5,000 seals since June 1999. This novel seal design, which consists of a locking, solid-concrete-block wall preloaded on the sides and near the mine roof with packsetter pumpable grout bags, is an important item in this company's product line. Burrell Mining Products has successfully commercialized a new lightweight concrete block seal design based on results from full-scale seal research in the LLEM. This design is easier to build, resulting in less musculoskeletal stress typically associated with conventional heavy solid-concrete-block designs and handling techniques. Since NIOSH's evaluation of the new seal design in June 2002, Burrell has been averaging about 70 seal installations per month.

A gob gas explosion occurred on or about June 16, 1995, where lightning initiated an explosion in a sealed section of the Gary 50 Mine in Pineville, WV. Several 4-foot-thick pumpable cementitious seal designs, which had been previously performance-tested in the LLEM and subsequently approved by MSHA, effectively contained the explosion, thereby sparing the miners working nearby.