"The U.S. Bureau of Mines is investigating strata interactions associated with mining of multiple coalbeds to provide the mining industry with improved methods of planning and developing multiple coalbeds, conserving resources, and increasing the safety of underground coal mining. The study involves analytical predictions and underground observations of longwall development ground control problems at a south-central Pennsylvania coal mine affected by subsidence induced by multiple-seam mining. As predicted, strata interactions were found in upper mine areas mined over lower mine gob. Observations revealed roof deterioration accompanied by excessive water inflows in the first 170 ft after crossing the gob line as mining entered and exited the subsided area (over the lower mine gob). In contrast, superimposed mine areas and areas mined a substantial distance out over the gob showed no signs of interaction with previous lower seam mining, again as predicted." - NIOSHTIC-2

NIOSHTIC no. 10001058

National Institute for Occupational Safety and Health