Evaluation of rockburst proneness considering specimen shape by storable elastic strain energy

To systematically assess the rockburst proneness considering specimen shape, multiple groups of laboratory tests were performed on 5 rock materials in cylindrical and cuboid shapes. The linear energy storage (LES) law of both cylindrical and cuboid rock specimens under uniaxial compressive load was confirmed, and the energy storage coefficient was found to be unrelated to specimen shape. On the basis of LES law, two rockburst proneness indexes, namely the strain energy storage index (Wet) and the potential energy of elastic strain (PES), were modified. Subsequently, the Wet, PES, peak‐strength strain energy storage index (Wetp)${W}_{\text{et}}^{{\rm{p}}})$, and peak‐strength potential energy of elastic strain (PESp) were used to assess the rockburst proneness of the cylindrical and cuboid specimens. In addition, the fragment ejection course of specimens under test was recorded by a high‐speed camera. Then, the rockburst proneness judgments obtained from the 4 indexes were compared with the qualitative data during rock destruction. The results show that, under similar stress conditions, specimen shape has an ignorable effect on the rockburst proneness as a whole. The judgment accuracy of the two modified indexes, especially that of the PESp, is favorably improved to evaluate the rockburst proneness of both cylindrical and cuboid specimens. However, misjudgment of Wetp${W}_{\text{et}}^{{\rm{p}}}$and PESpmay still occur in the assessment of rockburst proneness as these two indexes only consider the energy state before rock peak strength and the Wetp${W}_{\text{et}}^{{\rm{p}}}$is formulated in a ratio form. Rockburst proneness judgments from the four indexes were compared according to the qualitative information on rock failure. The results show that, under similar stress conditions, the specimen shape has an ignorable effect on the rockburst proneness as a whole. The judgment accuracy of the two modified indexes was favorably improved for the evaluation of rockburst proneness of both cylindrical and cuboid specimens, especially for the peak‐strength potential energy of elastic strain (PESp) index.