Summary: During raise bore operations of a 5 m diameter shaft, a rod string broke. The reaming cutter head fell 198 m onto a muck pile. No-go zones and barricading were in place (as per the mine’s procedure), therefore no workers were in the area or at risk.
Recommendations to industry: Before starting raise bore activities, condition monitoring tools such as non-destructive testing should be used to verify that equipment is fit for use.
Maintenance intervals for cutting consumables should be estimated before starting the task. Data such as geological assessments, test bores and historical data should be used to develop initial plans. Once raise boring begins, the estimated intervals should be reviewed and validated using actual data.