Rockburst-inspired controlled spontaneous fragmentation of hard rock via ultra-high frequency particle impact

Harnessing rockburst-the spontaneous fragmentation of high strain-energy hard rock-is a promising strategy for efficiently breaking hard rock in the high in situ stress environments of the deep Earth. However, safely controlling this spontaneous process remains a formidable challenge. Here, we demonstrate a method that uses an ultrasonic vibration field to actuate small-scale steel particles, generating ultra-high-frequency point-load impacts on exceptionally hard rock (unconfined compressive strengthå 150 MPa). These repeated, high-stress impacts rapidly initiate localized damage, which triggers a cascading release of the rock's intrinsic strain energy and leads to spontaneous fragmentation. Crucially, the process remains highly controllable: the rapid attenuation of the ultra-high-frequency action and the small localized influencing area confine the damage zone, ensuring safe and efficient spontaneous operation. Quantitatively, using our proposed Relative Comprehensive Damage Rate index, our findings indicate a 161.7% increase in rock fragmentation efficiency at 80 MPa confining pressure compared to the unconfined case, without any increase in external energy input. Our work thus demonstrates a strategy to safely harness the immense stored energy within deep rock, transforming a geological hazard into a highly efficient excavation tool.