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.
An 8760-hour calendar year (365 days × 24 h) is the universal denominator against which a mining fleet’s time is reconciled. Mechanical (physical) availability is the fraction of scheduled or calendar time a machine is mechanically capable of operating: PA = (calendar hours − hours down for repair/maintenance) / calendar hours × 100. It measures maintenance effectiveness, not whether the machine was actually used. Utilization is the fraction of the AVAILABLE hours the machine actually operated: U = operating hours / available hours × 100, and captures scheduling, standby, operator-shortage and weather losses on a machine that was mechanically fit to run. Use of Availability (UoA = operating hours / available hours, the same ratio phrased for dispatch) and the combined Effective Utilization (EU = PA × U) are the two figures fleet managers track together, since a high PA with a low U (equipment fit but idle) and a low PA with a high U (equipment run hard between frequent breakdowns) both hide a productivity problem that the single headline number does not show.
Operators can make both ratios look better than the underlying reliability really is by manipulating the denominator or the definition of “down.” Common tricks: (1) using scheduled hours (calendar hours minus planned shutdowns, holidays, standby shifts) instead of the full 8760-hour calendar base, which inflates every percentage by shrinking the denominator; (2) reclassifying weather, blast-clearance, power-outage or “no operator available” time as non-maintenance delay rather than down time, so it never counts against mechanical availability; (3) counting only unscheduled breakdown time against PA while excluding planned preventive maintenance (which can be a large, controllable block of hours) from the “down” total; (4) reporting fleet-average availability rather than per-unit figures, letting a few chronically down units be diluted by many healthy ones; and (5) reporting Use of Availability (operating/available) instead of overall Utilization (operating/calendar), which is always numerically larger because its denominator has already excluded down time. A careful reader always checks which denominator (calendar, scheduled, or available hours) and which delay categories were used before comparing two operations’ headline percentages.
