Challenges of mining the first right-handed longwall panel in a new reserve block in Pittsburgh Seam

Abstract

In this paper, the mining experience and challenges for the first right-handed longwall panel in the Pittsburgh Seam are introduced. The longwall headgate T-junction experienced very high face convergence (up to 61 cm), accompanied by roof sag, floor heave, and rib loading. The headgate convergence was so large that, in a few places, it threatened longwall retreat and ultimately required the bottom to be re-graded. Different underground instruments, such as a roof scope, de-gas drill, tell-tale, laser meter, and borehole pressure Cell (BPC), were employed to explore the roof geology and to monitor the entry convergence and the stress changes in the pillar. In addition, the impact of other geologic factors, such as large overburden depth, laminated sandstone roof geology, soft floor, and large headgate equipment, were also analyzed. Subsequently, geotechnical solutions were provided to avoid or mitigate the impact of these challenging geologic factors. Keywords: Coal mining, Horizontal stress, Ground control, Roof convergence