24-MMP-A5 Surface Mining Methods and Design · May 2013
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, 2013-May. 3 hours duration; one handwritten 8.5×11 in reference sheet permitted (not an open-book exam); only approved Sharp or Casio calculators allowed. Question 1 is compulsory (40 marks, parts 1.1–1.7); candidates then select FOUR of the six optional Questions 2–7 (15 marks each) to complete the paper.
Reference texts: Hartman & Mutmansky, SME Mining Engineering Handbook, 3rd ed. (dewatering, slope stability classification, dragline stripping geometry, truck dispatch, mine closure); Hustrulid, Kuchta & Martin, Open Pit Mine Planning and Design (moving-cone and Lerchs–Grossmann pit optimization, capital-cost estimating, truck-shovel match factor); Lerchs, H. & Grossmann, I.F. (1965) “Optimum Design of Open-Pit Mines,” CIM Bulletin (the graph-theoretic 2-D worked example this question is drawn from); O’Hara, T.A. (1980) “Quick Guides to the Evaluation of Orebodies,” CIM Bulletin, Feb. 1980, and Mular, A.L. & Poulin, R. (1998) CANCOST, CIM Special Volume 47 (capital-cost formulae); Bieniawski, Z.T. (1989) Engineering Rock Mass Classifications (RMR system).
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. Advanced bench. A second, higher bench is stripped ahead of (advanced beyond) the main dragline bench, usually by dozer, scraper or a smaller machine, so that the dragline is not required to cast the full overburden depth in a single lift. It is used when total overburden thickness exceeds the machine’s effective digging depth plus stacking height – splitting the column lets the dragline handle only the lower portion.
2. Key cut. A narrow pilot cut is taken first along one edge of the panel to create a void (a “key”) into which the dragline can begin casting; without it the first pass has nowhere to place spoil. It is necessary at the start of every new panel or block, and after any extended machine relocation, before normal side-casting can proceed.
3. Extended bench. The dragline works from a bench set back from (higher than) the coal, reaching down and out to both dig and cast, effectively extending its usable digging depth beyond the geometric limit of a single-level bench. It is used where overburden depth alone exceeds the machine’s rated digging depth but a second machine (advanced bench) is not economic.
4. Horseshoe configuration (2 marks). The dragline works around a U-shaped (horseshoe) panel, casting spoil into the void left by the previous two adjacent passes on three sides at once instead of one. It is used to shorten the average cast distance and increase spoil-placement capacity in an established mine where the block layout allows the machine to work the closing end of a panel, common where reach or stacking-height is marginal and every metre of average throw matters.
5. Pullback method. The dragline retreats from an already-cast spoil pile, re-handling previously placed material to build the pile higher or push it further back, freeing room at the front of the current bench for the next pass. It is necessary when the natural single-pass spoil geometry (as computed in Question 2 below) will not fit within the available strip width – i.e. the pile would otherwise encroach on the next cut’s working area.
