An index for evaluating rock failure using energy release and rock brittleness

Brittle failures such as rockbursts, stress-induced collapses, and spalling pose major risks in deep hard rock engineering, leading to safety incidents, project delays, and increased costs. While conventional brittleness indices are widely used to assess brittle failure susceptibility, they provide only qualitative assessments and cannot quantify the severity or extent of failure. To address these limitations, we conducted compressive tests on multiple rock types and developed a new brittleness index that captures post-peak ductile to brittle transition characteristics. Based on this index, the brittleness-based relative energy release (BRER) parameter was proposed, which integrates rock brittleness and confining pressure effects into post-peak energy release calculations. Field validation using acoustic testing and microseismic monitoring demonstrates that BRER reliably predicts both the risk and extent of surrounding rock failure, providing a comprehensive and practical tool for assessing and mitigating brittle failure in deep hard rock environments.