According to the current mineral economic context in which brownfield projects seems the preferred over greenfields, pre-splitting is a techniques that helps to make the pits deeper keeping them safe and more feasible by reducing waste removal. Rock slope management of any open pit is a complex process where many mining activities interact to come up with a safe and efficient slope design. From pre-splitting drilling and blasting perspective, bench face angle, borehole diameter and hole spacing are the most important parameters. In pre-splitting drilling, rock mass is an uncontrollable and fixed factor that has a determinant influence on pit slope design, drillability, borehole accuracy and cost. Among all physical rock properties, uniaxial compressive strength seems like the most relevant to predict percussive drillability. The drilling offering for pre-splitting is limited to percussive drilling systems because rotary drilling doesn´t fit due to too large hole size and lack of space for machine maneuvering next to the wall. Top Hammer is a very efficient drilling system for shorter holes and DTH for deeper holes. Pressurized airflow limits pneumatic drills performance; this is more evident in high altitude where up to 50% of efficiency might be lost in the Andean Region. The main suppliers of percussive drills are Sandvik and Atlas Copco. Customers in Perú prefer DTH drills for pre-splitting. To buy production drill machines customers use technical – economic KPIs like TCO (total cost of ownership) and TDC (total drilling cost). But to compare pre-splitting drilling machines it is needed a new metric, the cost per meter of wall (CPMW). To have accurate KPIs, availability and overall drilling cycle times (not just the rate of penetration) have to be accurate and reflect reality. Despite the customers´ preferences for DTH, Top Hammer seems like the most efficient from KPIs perspective. Pre-splitting drilling operation is very dangerous because the equipment is in operation next to the wall and explosives. Safety features of the machine may reduce significantly the risks. Among the safety features, remote drilling system eliminates the risk for the operator, making this the greatest competitive advantage. It is concluded that top hammer drilling system (DP1500) is the most economical and DTH (Smart ROC D65, upgrade of ROC L8) is the safest. This study is based on Peruvian open pit mines with information coming from Antamina Mine, Barrick Lagunas Norte and Toquepala Mine.
|Translated title of the contribution||Application of Percussive Drills in Open Pit Mines for Pre-Splitting|
|Publication status||Published - 2016|