24-MMP-A5 Surface Mining Methods and Design · May 2015
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, 2015-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 FOUR of Questions 2–7 (each worth 20 marks).
Reference texts: Hartman & Mutmansky (eds.), SME Mining Engineering Handbook, 3rd ed. (equipment availability/utilization, dragline stripping systems, truck-shovel productivity, mine dewatering, mine cost estimation); 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, discounted cash-flow 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; O’Hara, T.A. (1980), CIM Bulletin (Feb. 1980), and Mular, A.L. & Poulin, R. (1998), CapCosts: A Handbook for Estimating Mining and Mineral Processing Equipment Costs, CIM Special Volume 47 (parametric capital-cost formulae used in Question 6); Theis, C.V. (1935) and Cooper & Jacob (1946) aquifer-test methods (standard hydrogeology references, Question 3.2).
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.
1.3.1 – Water hammer. Water hammer is a transient pressure surge (positive or negative) that propagates through a pipeline as an acoustic pressure wave when the flow velocity is changed suddenly – a pump trip, a rapidly closing valve (the check valve considered in Question 3.1.5), or a pump start against a full column. The moving water's momentum cannot stop instantaneously, so its kinetic energy converts abruptly into a pressure pulse (Joukowsky surge, $\Delta P=\rho\,a\,\Delta v$, where $a$ is the pipeline's acoustic wave speed) that travels back and forth along the pipe until friction dissipates it.
1.3.2 – Two major effects. (1) Over-pressure – the positive surge can spike well above the pipe's and fittings' rated working pressure, causing pipe rupture, joint/coupling failure, or damage to pump casings and valves – directly relevant to the HDPE riser sized in Question 3.1.4. (2) Column separation / vacuum collapse – the accompanying negative-pressure phase (particularly on the suction side after a pump trip, or at a high point in the profile such as the 1695 m tandem-pump elevation of Question 3.1) can drop local pressure below vapour pressure, causing the liquid column to separate; when the column subsequently rejoins, the resulting secondary impact can be even more damaging than the initial surge, and sustained vacuum can also collapse a thin-walled pipe.
1.3.3 – Mitigation. Slow, controlled valve operation (a slow-closing, non-slam check valve rather than an instantaneous swing check); surge/pressure-relief valves or air-vacuum (combination air) valves at high points and near pumps, to bleed off over-pressure or admit air rather than let a vacuum develop; pump/motor soft-start and controlled ramp-down (VFDs) to avoid abrupt velocity change; surge tanks, air chambers, or a standpipe on long risers to absorb the pressure wave; and, at the design stage, keeping flow velocities moderate and selecting pipe with a pressure rating that carries an adequate margin above the calculated static AND transient pressure for that specific pipeline profile.
