24-MMP-A5 Surface Mining Methods and Design · December 2018
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
Reference texts: Hustrulid, Kuchta & Martin, Open Pit Mine Planning and Design (3rd ed.) — truck-shovel match factor, dragline stripping geometry, capital cost indexes, open-pit scheduling; SME Mining Engineering Handbook (3rd ed.) — equipment costing, mine dewatering, cost-index escalation.
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.
Applying Pareto’s Law. Pareto’s Law (the 80/20 rule) states that roughly 80% of a cost centre’s total cost is generated by roughly 20% of its individual cost line items. Applied here: sort every accounting line item within each cost centre (drilling, trucking, loading) by dollar value, largest first, and focus cost-reduction effort ONLY on the handful of items at the top of that ranked list — typically 2–3 consumable items per centre — rather than spreading management attention evenly across dozens of minor line items that collectively move the total very little. This concentrates limited engineering/procurement effort where it has the largest leverage.
4.1.1 Drilling (blast-holes) — two major consumables. Drill bits/rock bits (≈40–45% of drilling consumables cost, the single largest item in hard, abrasive rock) and drill rod/pipe/stabilizers (≈20–25%) typically dominate; explosives-adjacent items (bit lubricant, dust-suppression water) are minor by comparison.
4.1.2 Truck (haulage) — two major consumables. Tyres (≈35–45% of truck consumables — a single large rigid-frame haul-truck tyre set can be one of the highest unit costs in the entire mine) and ground-engaging/wear parts (dump-body liners, brake linings, ≈15–20%) are the two dominant consumable lines, well ahead of items like filters or hydraulic fluid.
4.1.3 Shovel (loading) — two major consumables. Ground-engaging tools (bucket teeth, lip shrouds, wear plates, ≈35–40%) and wire rope / dipper trip cable (on a cable shovel) or hydraulic hoses and seals (on a hydraulic shovel), ≈15–20%, are the dominant consumable lines.
| Cost centre | Item 1 (approx. %) | Item 2 (approx. %) |
|---|---|---|
| Drilling | drill bits, ≈40–45% | drill rod/stabilizers, ≈20–25% |
| Truck haulage | tyres, ≈35–45% | wear parts (liners/brakes), ≈15–20% |
| Shovel loading | ground-engaging tools, ≈35–40% | rope/hoses & seals, ≈15–20% |
4.1.4 — inflation cost indexes and future estimates. Applying a SEPARATE, appropriate cost index to EACH Pareto-identified major consumable (a steel/commodity index for drill bits and GET, a rubber/oil-linked index for tyres) — rather than one blanket mine-wide index — lets a future operating-cost estimate track the real drivers of that centre’s cost far more accurately than escalating the WHOLE cost centre uniformly, because the top 2–3 Pareto items dominate the total and each tracks a different commodity market; this is the direct link between the cost-indexing discussion of Question 1.3 and the consumable-level detail Pareto analysis exposes here.
