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According to Weiss, federal regulations for seal use require all mined-out areas to be ventilated or sealed off from active sections. When an operation plans to perform sealing, it must be ensured that the design is “deemed suitable” by the US Mine Safety and Health Administration – and a portion of that suitability meter has been determined by some of Lake Lynn’s full-scale explosion tests.

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Up until July 19 of last year, US regulations were twofold for seals: the ability to withstand a “static” explosion that would create up to 20psi of overpressure; and to not leak more than 100 cubic feet each minute at 1in water pressure differential at any given location of the seal.

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The experimental complex found that unconfirmed explosion test methods were able to speak to the 30 CFR-horizontal “static” pressure requirements. Following construction of seals and observations of the after-effects of an explosion within the mine, 11 types of alternative seals making up more than 30 designs successfully passed the agency’s suitability determination.

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Weiss outlined the chamber approach to evaluating seals, considered an alternative approach to measuring strength of seals to the confines of MSHA’s 30 CFR 75.335. Two chambers were developed, a small one measuring 21ft wide by 8ft high, and a larger one with the dimensions of 30ft wide by 16ft high.

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The method is meant to show the comparison between Lake Lynn Experimental Mine, or regulators’ current approved method, and alternative measurement methods to determine the design factors, including size, that would produce a safe seal – and, vitally, a seal’s ultimate strength when constructed within a coal mine.

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To simulate an explosion, researchers used alternate pressure loading methods in the chambers (which were closed during the experiment), including compressed air and water.

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The chamber testing results reflected results comparable to prior LLEM explosion tests, they said.

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“In-situ pressure loading with water shows promise as an alternative to full-scale explosion testing of mine seals,” the researchers said.

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Additionally, it was found that the method could also measure ultimate strength of seals, fundamental to seal design.

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Researchers also looked at “head on” pressure loading, which also consisted of a confined experiment that would this time include an explosion of higher intensity and longer duration. The blast would uniformly impact the full face of the seal.

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A new LLEM test configuration was developed by the group and efforts for the testing are still ongoing. Weiss said the agency continues to examine “generic methods” to improve in-situ seal strength.