24-MMP-A5 Surface Mining Methods and Design · May 2014
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
EGBC National Exam — Mining and Mineral Processing Engineering, 09-MMP-A5 Surface Mining Methods and Design, 2014-May. 3 hours duration, closed book; one hand-written 8.5×11 inch reference sheet and an approved Casio or Sharp calculator permitted. Question 1 is compulsory (40 marks, all six parts 1.1–1.6); a candidate then selects THREE of Questions 2–6 (each worth 20 marks).
Reference texts: Hartman & Mutmansky (eds.), SME Mining Engineering Handbook, 3rd ed. (dragline stripping systems, truck-shovel productivity, mine cost estimation — the primary reference throughout this paper); Hustrulid, Kuchta & Martin, Open Pit Mine Planning and Design, 3rd ed. (block-model economics, floating/moving-cone algorithm, the Lerchs–Grossmann graph-theoretic pit-optimization method, annual push-back scheduling); Kennedy, B.A. (ed.), Surface Mining, 2nd ed., SME (dragline range-diagram geometry, stripping methods); Lerchs, H. & Grossmann, I.F. (1965), “Optimum Design of Open-Pit Mines,” CIM Bulletin, 58, 47–54.
Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.
Short-term planning (shift, weekly, monthly schedules) works from surveyed, drilled-and-blasted, grade-controlled block data, allocates specific shovels/trucks/drills to specific benches and blends to meet the mill’s daily grade and tonnage targets, and is re-optimized continuously as new grade-control and equipment-availability data arrive. Long-term planning (annual pushback schedules through life-of-mine, as in Question 4 below) works from the resource block model and an economic ultimate-pit-limit optimization (Question 6), sets the pushback sequence, waste-stripping profile, equipment fleet size and mill-feed strategy over 5–20+ years, and is revisited only annually or when reserves/prices materially change.
Advantages of short-term planning: reacts quickly to grade-control and equipment reality, protects mill feed quality shift-by-shift, catches geotechnical/dilution problems early. Disadvantages: myopic — optimizing this week’s cash flow can high-grade the deposit and strand lower-grade ore that a longer view would have sequenced differently, and it cannot by itself decide pushback timing or fleet size. Advantages of long-term planning: sets the pit limits, pushback sequence and capital equipment purchases that short-term planning must live within, and captures the time-value-of-money trade-off between early low-cost/high-grade cash flow and total resource recovery. Disadvantages: built on a resource model and price forecast that carry real uncertainty (a 20-year price/geology assumption is rarely exactly right), and is too coarse to catch day-to-day grade-control or equipment issues, so a mine must run BOTH horizons together — long-term planning sets the envelope, short-term planning operates inside it — rather than substituting one for the other.
In practice the two are reconciled through periodic reconciliation: actual short-term production and grade-control results are compared against the long-term plan's assumptions at each period end, and material deviations (systematic over- or under-recovery of grade, faster or slower-than-planned advance rates) trigger a re-run of the long-term schedule rather than being silently absorbed into next month's short-term plan. This feedback loop is why the routine EMPLOYMENT of both horizons matters as much as their individual methodology — a mine that plans long-term once at the start of life and never reconciles it against short-term reality will drift, often without anyone noticing until the pit limits themselves need revisiting years later than they should have been.
