What is the purpose of using benching techniques in open-pit mining excavation, and how does it improve safety?

Benching techniques in open-pit mining excavation involve creating a series of horizontal steps, or benches, along the sides of the pit. This method serves primarily to improve slope stability and enhance safety. Without benching, the steep, continuous slopes of an open-pit mine are prone to landslides and rockfalls, which pose a significant risk to personnel and equipment. Each bench acts as a catch basin to contain falling rocks and debris, preventing them from rolling down the entire slope and causing damage or injury. By breaking the slope into smaller, more manageable sections, benching reduces the overall height and angle of the slope, which increases its stability. The width of each bench is designed to provide a safe working area for equipment and personnel. Benches also provide access roads for haul trucks and other vehicles to transport ore and waste rock. The bench height and width are determined by factors such as the type of rock, the slope angle, and the size of the equipment being used. For example, in a mine with unstable rock formations, the benches may be narrower and more frequent to provide greater support. Benching also facilitates selective mining, which is the process of extracting specific ore types or grades. By creating benches, miners can access different layers of ore more easily and selectively remove the desired material. This improves the efficiency of the mining operation and reduces waste. In addition to improving slope stability and safety, benching also improves visibility within the mine. The benches create a more open and accessible working environment, making it easier for operators to see and avoid hazards. Proper bench design also allows for effective water management. Benches can be sloped slightly to direct water away from the slope face, preventing erosion and instability. Overall, benching is an essential technique for ensuring the safety and efficiency of open-pit mining operations. It reduces the risk of landslides and rockfalls, provides safe working areas, and facilitates selective mining and water management.