Abstract
This article presents a novel stochastic optimization model that simultaneously optimizes the short-term extraction sequence, shovel relocation, scheduling of a heterogeneous hauling fleet, and downstream allocation of extracted materials in open-pit mining complexes. The proposed stochastic optimization formulation considers geological uncertainty in addition to uncertainty related to equipment performances and truck cycle times. The method is applied at a real-world mining complex, stressing the benefits of optimizing the short-term production schedule and fleet management simultaneously. Compared to a conventional two-step approach, where the production schedule is optimized first before optimizing the allocation of the mining fleet, the costs generated by shovel movements are reduced by 56% and lost production due to shovel relocation is cut by 54%. Furthermore, the required number of trucks shows a more balanced profile, reducing total truck operational costs by 3.1% over an annual planning horizon, as well as the required haulage capacity in the most haulage-intense periods by 25%. A metaheuristic solution method is utilized to solve the large optimization problem in a reasonable timespan.
Highlights
Short-term mine planning generally aims to make optimal decisions over a timeframe of days to months to best meet annual production targets given by the longterm mine production plan (Wilke and Reimer 1977; Fytas et al 1987; Hustrulid et al 2013)
The second step optimizes the assignment of mining equipment in open pit mines and is referred to as fleet management (Afrapoli and Askari-Nasab 2017)
The mathematical model for joint stochastic short-term production scheduling and fleet management optimization for mining complexes is formulated as a stochastic integer programming model with fixed recourse (Birge and Louveaux 2011), and builds upon the simultaneous stochastic optimization of the components of a mining complex that are pertinent to long-term mine planning (Goodfellow 2014; Goodfellow and Dimitrakopoulos 2016, 2017)
Summary
Short-term mine planning generally aims to make optimal decisions over a timeframe of days to months to best meet annual production targets given by the longterm mine production plan (Wilke and Reimer 1977; Fytas et al 1987; Hustrulid et al 2013). Recent developments combine aspects of fleet management and short-term extraction sequencing for open pit mines with the motivation of creating synergies between the steps that are conventionally optimized separately; this, in turn, generates more efficient short-term plans (Fioroni et al 2008; L’Heureux et al 2013; Torkamani and Askari-Nasab 2015; Mousavi et al 2016a; Villalba Matamoros and Dimitrakopoulos 2016; Blom et al 2017; Kozan and Liu 2018; Upadhyay and Askari-Nasab 2018) Most of these recent approaches integrate shovel allocation decisions, shovel capacities and the cost of shovel movements in the production scheduling model.
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