Benchmark Drill and Blast and Mechanical Excavation Advance Rates for Underground Hard-Rock Mine Development

Faster development rates in underground mines would generate value by reducing the time from capital expenditure (development) to revenue generation. This paper compares advance rates and costs for drill and blast and mechanical development methods based on mining and construction case studies. The drill and blast cycle consists essentially of three sets of series-linked processes: 1. drilling, charging, blasting, and ventilation, 2. mucking, and 3. scaling and installation of preliminary ground support. Mechanical excavation is inherently a faster process as excavation, mucking and ground support can be executed as parallel processes. This is reflected in average advance rates that vary between 4 to 9 m/day for drill and blast operations for typical section areas, as compared to between 8 and 45 m/day for mechanical excavation. As ground conditions become more difficult, the productivity of mechanical excavation systems generally decline as roof support activities become the critical path. The paper examines process re-engineering opportunities for drill and blast methods and concludes that, at best, even if all three of the above process could be performed in parallel, the theoretical limit to drill and blast development is approximately 19 m/day. The paper identifies a number of process re-engineering opportunities including the possibility of further investigating ‘hybrid’ excavation methods that combine the flexibility and risk mitigation of drill and blast with the speed of mechanical excavation. BACKGROUND