ABSTRACT:

Time-dependent roof deformation around coal mine intersections has received little importance in the past. A comprehensive understanding of the effect of time is critical to eliminate the potential for roof falls around intersections and the associated risk to worker safety. To that end, this study utilized a precise total station approach for measuring the 3D displacements (X-, Y- and Z-) of targets spatially distributed around an intersection. The study was conducted at a coal mine in western Kentucky, and measurements were made on four different dates from March-July 2016. The measured horizontal displacements were found to be larger than the vertical displacements, probably a consequence of the strong roof strata at this location. Analysis of the horizontal strain components indicated that most of the strain values were less than 0.5%. The progressive increase in rib sloughing around the mid-height of coal pillars was indicative of continuing vertical and horizontal displacements, which was supported by field observations.

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