Mining in focus
In the case of an opencast mine, mine planning will also take geological, product specification, and equipment sizing into consideration.
quality cut-offs, and geological losses. Choosing an approach to dilution and loss will relate primarily to the assumed mining equipment, quality considerations, and the economic margin of the ore. There are three main approaches, namely inclusive, exclusive, and standard. Product specifications and the associated cut-offs that define volumes of saleable product are traded off against typical economic mining cut-off grades.
Based on the drilling samples, the economic interval of the mineralised reef or ore body can be determined. The‘ best cut’ must then be determined by the mine planner. The‘ best cut’ refers to the optimal high to which an underground face and resulting tunnel can be developed.
This‘ best cut’ calculation must consider the grade of the material and the client’ s requirements as determined by the marketing department, such as element ratios. The mine planning also needs to consider the limitations of the mining equipment. The minimum physical dimensions for the trackless machinery to operate, such as height with canopy and turning angle, needs to be factored in. The face height will also be determined by the safe operating limits, such as the reach height of the drill rig boom and roof bolters. The mining method and the resulting environmental requirements will also determine the mine plan. An example would be board-and-pillar mining operations, where the layout of the mine would resemble a Christmas tree, to optimise ventilation and cycle times from the face to the main drive.
Planning an open pit
In the case of an opencast mine, the mine planning will also take geological, product specification, and equipment sizing into consideration. The geotechnical characterisation of the host rock will determine the bench heights. The amount of overburden that needs to be removed to reach the ore will determine the stripping ratio. The block model will then be developed and various scenarios applied, through approaches such as
Whittle Optimisation, to determine the pit shell. The physical limitation of the drill rigs that drill the blast holes and the effectiveness of the emulsion explosives both have an impact on the fragmentation, which affects the load and haul capacity and the cycle times of the trackless equipment.
Mine planning and scheduling also need to be able to adjust the short-term planning in case a deviation is required. This could be intersecting blind dykes or faults or having working faces declared unsafe due to insufficient ventilation or support. The short-term mine plan then needs to be adjusted to minimise the lost time by doing a trade-off between moving to a new working face, processing stockpiles or lower-grade material, or surface blending of stockpile material. The mine schedule also needs to consider the average advance per blast and the cycle time. The cycle time refers to the time it takes to prepare a face for blasting, making the area safe to access, load, and haul the blast heap material; installing support;