Problem Statement
Grade Engineering (GE) is the function and set of activities enabling the early discard of barrenMaterial void of any valuable elements. or uneconomic rock (low grade mineralised rock) prior to processing the run of minePost blast material in the load/haul cycle. (RoM). The location where GEGrade Engineering activities can take place is not necessarily fixed and generally are either close to, or at the mining faceActive area of shovel/truck loading operations. or near the crushing circuitGeneral term for a collection of comminution/flotation equipment. (outside of the mining operations). The additional activities in handling the rock and to ultimately discard barrenMaterial void of any valuable elements. or low metal content rock, means additional equipment interfaces are introduced. More interaction and possibly more rehandling of rock impacts equipment cycle timeTime taken for a single truck to go from shovel/dig face to destination.s and potentially introduces additional equipment requirements.
GE therefore needs to prove that these impacts are covered i.e. the delta economic benefit of GEGrade Engineering should greatly outweigh the delta cost of introducing additional (potential) productivity impacts and cost. Another key factor in improving equipment productivity is the introduction of newer technology including automation. The following advances in mining equipment technology are showing significant promise:
GE therefore needs to prove that these impacts are covered i.e. the delta economic benefit of GEGrade Engineering should greatly outweigh the delta cost of introducing additional (potential) productivity impacts and cost. Another key factor in improving equipment productivity is the introduction of newer technology including automation. The following advances in mining equipment technology are showing significant promise:
- Autonomous equipment
- drill rig automation
- Semi-remote and remote loading units (not autonomous)
- Advancements in equipment dispatchSystems for allocation of equipment plans (eg. Trucks, shovels etc…). technology
Equipment dispatchSystems for allocation of equipment plans (eg. Trucks, shovels etc…). technology have been around for many years yet ensuring that the dispatchSystems for allocation of equipment plans (eg. Trucks, shovels etc…). controls are optimised and followed still require more labour and effort.
Grade Engineering Mine Planning
The implementation of any GEGrade Engineering option involves the analyses of the rock, the identification of the most appropriate method and application for the project or operation and to then commence with the planning and simulation of mine plans to meet the required processing feedMaterial entering a predetermined system. targets. Some operations and many new projects often see the processing plant as the facility that is added to the back end of the mining operation.
A mining operation is a processing plant needing to recover the most metal for the least amount of effort and it requires a supply of rock, tailored for that processing facility. This means the hole in the ground (the mine) needs to supply the best rock to the processing facility which is responsible for generating the revenue. The mine must now identify how it is able to meet the demands of the processing facility and doing that with the least amount of diesel, power and labour. This is where GE mine planning is key. The process flow (Figure 2 1) depicts the mine planning process with GE:
A mining operation is a processing plant needing to recover the most metal for the least amount of effort and it requires a supply of rock, tailored for that processing facility. This means the hole in the ground (the mine) needs to supply the best rock to the processing facility which is responsible for generating the revenue. The mine must now identify how it is able to meet the demands of the processing facility and doing that with the least amount of diesel, power and labour. This is where GE mine planning is key. The process flow (Figure 2 1) depicts the mine planning process with GE:
Figure 2-1: GE mine planning Activity flow
Although it seems that GE mine planning follows the same activity flow as traditional mine planning, with GEGrade Engineering there are several options to be tested (firstly by looking at all possible option economics i.e. revenue minus total cost). If there is a clear economic benefit with the introduction of GEGrade Engineering in the mine planning approach, then the mine plans look to optimize the GEGrade Engineering options which often require several feedMaterial entering a predetermined system. back and data loops potentially impacting to the input block model and mine optimization activities.
Once the Long-Range/Strategic mine plan is sound (after several iterative optimisation analyses with GEGrade Engineering strategies) the Medium range and Short-Range planning activities revolve around designing and scheduling a practical solution at equipment, consumables and labour level of detail. This is often where the Medium-Range mine plan could likely feedMaterial entering a predetermined system. back to the Strategic or Long Range mine planning activities again for more optimisation and planning iteration.
- Development of a grade block model
- Analyses of the possibly GEGrade Engineering methodologies and their possibly impacts for the given orebody
- Development of a GEblock model, which is essentially the addition of several GEGrade Engineering fields to the existing grade or geology block model
- The addition of GEGrade Engineering Rank-Response Factors and ultimately mass pullRelative proportion of feed mass in the accept stream after preconcentration.s and upgrade factorGrade of accept material divided by feed grade. fields to the geology block model
- Calculation of the NSR and costs associated with eachGEGrade Engineering option and its upgrade factorGrade of accept material divided by feed grade.s
- Mine optimisation (open pit Optimisation or underground stope Optimisation) with and without GE. This is to develop a non-GE mining footprint and economic limits and the GEGrade Engineering economic mining limits.
- Analyse the impacts of different GEGrade Engineering methodologies to the economic perimeters or stope shapes. This will provide the very important deliverable of orebody sensitivity to GE mine planning.
- There may also be the ability to consider ore sorting and for that the mine planners require a Uniform Conditioned block model or additional grade fields identifying the heterogeneity of the orebody within a potential mining block.
- If sensing and sorting is being considered, the potential for differential blasting would also be considered, although these steps involve more risk and unknowns being introduced with an already unknown statistically estimated dataset.
- The mine optimizations are then run for all possible options of GEGrade Engineering and then for the base mining and processing case simply using the calculated break-even and marginal Cut-Off points
- The Long-Range/Strategic mine plan is then developed (annual mining areas identified, and the ore destinations scheduled with and without GE). These mine plans go further to simulate the total rock, ore and wasteMaterial determined to be below a predetermined grade or economic threshold. and GEGrade Engineering blocks to be mined to enable the supply of appropriate ROMRun of mine to the process plant, whether it entails some pre-processing GEGrade Engineering or not.
- The GEGrade Engineering Long-Range mine plan is then developed including equipment, labour and consumables (energy/power, diesel, explosives etc.) to fully utilise the processing plant capacity but with an improved ROMRun of mine feedMaterial entering a predetermined system. possibly meaning a higher mining rate
- The Medium Range mine plans are then developed to test the Long-Range mine plans for GEGrade Engineering on a quarterly and monthly reporting details. Often there are challenges identified when developing monthly production scheduleExtraction sequence determined to produce optimal outcomes from long-term mine plan.s and these challenges needs to be resolved back in the Long-Range mine plan. This is essential as it might impact the Strategic mining sequence.
- Once the Long-Range and Medium-Range mine plans are adequately and practically resolved and still demonstrate an optimal GE mine plan the next step is to then develop the Equipment simulations and to fully model the likely productivity impacts of a GE mine plan.
- The equipment fleetAvailable equipment at a given operation (e.g. trucks, shovels, water trucks etc…).s and productivity impacts are vital and again could feedMaterial entering a predetermined system. back further changes/refinements that might be required, either on the Medium-Range mine plan or even all the way back to the Long-Range mine plan. Experience shows that it generally only requires some adjustments to the Medium-Range mine planning as the granularity on a Long-Range mine plan is reasonably low and allow for shorter term fluctuations still providing similar requirements on an annual mine planning basis.
- The Equipment productivities impact fleet selection, rock transportation considerations and even mine design. It is therefore key to test and understand the possible impacts that a GE mine plan could have on the mining equipment productivities and the fleet cycle timeTime taken for a single truck to go from shovel/dig face to destination.s.
- Event simulations are not widely considered or practiced by mine planners yet is becoming necessary as subtle changes to mining areas and increased production requirements due to GEGrade Engineering and low grade or wasteMaterial determined to be below a predetermined grade or economic threshold. rock rejection prior to processing could impact the mining equipment cycles. Most mine planning software solutions enables the simulation of equipment, yet the software calculations are predicated on the key inputs like tramming distance, equipment loading rates, typical impacts and non-productive times and time impact nodes along the mine production roads and faces. Having to move a shovel or excavator a couple more times a day to optimise the GEGrade Engineering and high-grade mining faceActive area of shovel/truck loading operations.s could lead to slower loading rates. This could lead to more truck queueing and therefore longer truck cycle timeTime taken for a single truck to go from shovel/dig face to destination.s. This in turn leads to more trucks and/or more trucks and shovels required.
- If the Equipment productivities are not modelled and tested and the potential impacts not well-understood, the mine plans could have serious omissions and when implemented, the operational GEGrade Engineering might not yield the modelled benefits.
The mine plans therefore require diligent planning and includes several equipment productivity-analyses. The equipment productivities being modelled should also cater for some proven unknowns and unlikely events to ensure the process and mine plan is robust and can deal with changes or impacts.