Production planning under special constraints

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The Iduapriem Gold Mine intends to mine 1.22 million bank cubic meters (3.24 million tonnes) of material from its most resourceful pit, Block 2, using two loading machines and a fleet of Cat 773B rear dump trucks. The waste to ore ratio of the material to be mined is 4: 1. The material should be mined at minimum cost, within time limit of 3 months, and must meet the milling plant capacity. However, operational constraints such as machines breakdowns, poor state of haul roads, effect of weather changes, dump sites restrictions, dewatering problems, power outages of the milling plant and shift time underutilsation, make the achievement of this production target difficult. Any workable plan that will accomplish the set production target must take into consideration these inevitable operational constraints. In this work, the open pit operations at Iduapriem Gold Mine is studied with particular reference to material movement between active mining pit Block 2 and the dumping points for ore and waste. The operational constraints associated with material movement are also studied. The production problem of the mine is analysed to have single objective that is mining 1.22 million bank cubic meters of material at minimum cost under operational constraints. The activities involved in material movement and the inherent restrictions and set-up conditions that must be satisfied in material movement are identified. By time and motion studies on the activities (load, haul, manoeuvre and dump, and return) associated with material movement, and from the planning department relevant data associated with material movement has been assembled and systematically analysed. Proceeding from the data analysis, a complete Linear Programming (LP) model that fully represents the production problem of the Iduapriem Gold Mine is developed. The Linear Programming (LP) model of the production problem has been solved using the Linear Interactive Discrete Optimizer (LINDO), a computer programme which utilises an algonthm of the Simplex method. The solution to the LP problem is a comprehensive short-term production plan that will accomplish the objective of the mine. Sensitivity analysis has been carried out on the optimal solution to check for useful changes within the production plan.
A thesis submitted to the Board of Postgraduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirement for the award of the Degree of Master of Science in Mining Engineering, 1998