Abstract
This study uses an extensive suite of borehole pressure cell (BPC) data from a US longwall mine to better characterize the global stress redistribution process during mining. A new methodology employing the Bieniawksi’s strength gradient equation was used for converting the BPC measurements into rock pressure. It was observed that the Bieniawksi gradient equation underestimates coal strength for points located deeper into the pillar. Comparisons with previous empirical and analytical equations are also presented for different stages of longwall loading. Very low front abutment load in comparison to the side abutment load was observed, along with a low abutment angle for this mine. This abutment angle value was verified from stress measurements made within the solid coal face ahead of the advancing panel. Some other atypical trends were noted during data analyses, such as a monotonic drop in stress from the panel edge within the coal face; these trends were explained using an elastic FLAC3D model. Finally, the load distribution in a pillar is presented in three-dimensions using interpolated bar graphs for different locations of the longwall face.
Published Version
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