24-MMP-A5 Surface Mining Methods and Design · December 2016
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
Surface Mining Methods and Design (09-MMP-A5) — December 2016 National Exam. Compulsory Question 1 (six sub-questions) plus all five optional Questions 2–6 are answered in full below (candidates select only three of Questions 2–6 in the real exam; all are solved here as a complete study resource).
Reference texts: Hustrulid, Kuchta & Martin, Open Pit Mine Planning and Design (3rd ed.) — pit optimization, Lerchs–Grossmann, floating cone, dragline stripping geometry; SME Mining Engineering Handbook (3rd ed.); BC Health, Safety and Reclamation Code for Mines; Newnan, Eschenbach & Lavelle, Engineering Economic Analysis — sinking funds and future-worth factors.
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.
Water hammer is the transient pressure surge (positive or negative) generated when a moving column of water in a pipeline is suddenly decelerated or accelerated — typically by a pump trip, a valve closing/opening quickly, or a check valve slamming shut — converting the fluid's kinetic energy into an elastic pressure/compression wave that propagates along the pipe at the speed of sound in the pipe/fluid system (the Joukowsky surge, Δp = ρ•a•Δv).
(1) An over-pressure surge that can exceed the pipe's or fittings' pressure rating, causing pipe rupture, flange/joint failure, or damage to the pump casing and check valves. (2) A negative-pressure (vacuum) transient on the rebound of the same wave, which can pull the pipeline below vapour pressure, causing column separation/cavitation and, on the subsequent collapse of the vapour cavity, a second, often more damaging secondary hammer pulse; a sustained vacuum can also collapse a thin-walled or under-rated pipe.
Slow valve closure/opening times (closure time greater than the pipeline's critical period 2L/a), soft-start/soft-stop VFDs on pumps to ramp flow rather than step it, surge/relief valves or air chambers (surge tanks) sized to absorb the transient, non-slam (spring-loaded or slow-closing) check valves rather than swing checks on a rapidly reversing line, and air-release/vacuum-breaker valves at high points to prevent column separation — several of which are directly relevant to the tandem-pump check-valve scenario examined in Question 5.1.5 below.
