What is the primary reason for using pre-splitting techniques in open-pit mining?

The primary reason for using pre-splitting techniques in open-pit mining is to create a clean, stable, and controlled final pit wall, reducing the risk of slope failure and minimizing damage to the remaining rock mass beyond the designed pit limits. Pre-splitting involves drilling a line of closely spaced holes along the planned pit wall and then detonating a lightly loaded explosive charge in these holes. The controlled explosion creates a continuous fracture or crack along the line of holes, effectively separating the rock mass that will be excavated from the rock mass that will form the final pit wall. This fracture acts as a stress relief zone, preventing the shock waves from subsequent production blasts from damaging the rock mass beyond the pre-split line. This reduces the risk of overbreak, which is the excavation of rock beyond the designed pit limits. Overbreak can lead to slope instability and increased waste removal costs. Pre-splitting also creates a smoother, more uniform pit wall, which improves the long-term stability of the slope. A rough or fractured pit wall is more susceptible to weathering and erosion, which can lead to slope failure. By creating a clean, stable pit wall, pre-splitting reduces the need for expensive slope stabilization measures, such as shotcreting or rock bolting. In addition to improving slope stability, pre-splitting can also reduce the amount of ground vibration generated by blasting. The pre-split fracture acts as a barrier to the transmission of seismic waves, reducing the impact of blasting on nearby structures. Pre-splitting is a cost-effective technique for improving the safety and efficiency of open-pit mining operations.