Investigation of the influence of grain-scale heterogeneity on strainburst proneness using rock-like material

As mining and tunnelling projects advance to deeper areas, strainbursts occur more frequently. This failure mode is extremely dangerous, as the rock mass fails abruptly, releasing high amounts of energy. This poses a high risk to the life of workers and equipment used. For a robust strainburst risk assessment many factors have to be taken into account. Besides geological features, overburden, excavation method, etc., rocks’ intrinsic proneness to strainburst plays a major role. Whether a rock tends to this failure behaviour depends strongly on the rocks’ mechanical and structural characteristics at the grain-level, especially on its heterogeneity. The authors demonstrate this based on different rock-like sample sets, consisting of a very fine-grained fibreless ultra-high-performance concrete (UHPC) and a constant volumetric fraction of coarse aggregates. Thereby, the heterogeneity aspect was introduced by the different properties of the aggregates. A laboratory program was performed, taking into account uniaxial compression tests (including post-failure tests to evaluate the failure energy) and Acoustic Emission Testing (to monitor the cracking activity). The study underlines the high suitability of using Acoustic Emission Testing (AET) in strainburst risk assessment. In addition, the authors analyse empirical parameters commonly used to evaluate rocks’ intrinsic proneness to strainburst, and give recommendations regarding their application. Overall, the study substantiates former research and emphasises the usefulness of petrographic information within strainburst risk analysis. It also sets the base for future research on real rock, which will hopefully lead to more specific recommendations for practitioners on how to include rocks’ grain-scale characteristics in strainburst risk analysis.