Openpit fundamentals

Open Pit Mining Fundamentals : 

Open Pit Mining Fundamentals Venkat

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2 Terminology BENCH: Ledge that forms a single level of operation above which mineral or waste materials are mined from the bench face.

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2 Terminology BENCH HEIGHT: Vertical distance between the highest point on the bench (crest) and the lowest point or the bench (toe). It is influenced by size of the equipment, mining selectivity, government regulations and safety.

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2 Terminology BENCH SLOPE or BANK ANGLE : Horizontal angle of the line connecting bench toe to the bench crest.

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5 BERM: Horizontal shelf or ledge within the ultimate pit wall slope left to enhance the stability of the a slope within the pit and improve the safety. Berm interval, berm width and berm slope angle are determined by the geotechnical investigation. Terminology

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5 OVERALL PIT SLOPE ANGLE: The angle measured from the bottom bench toe to the top bench crest. It is the angle at which the wall of an open pit stands and it is determined by rock strength, geologic structures and water conditions. Terminology

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5 The overall pit slope angle is affected by the width and grade of the haul road. Terminology

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8 HAUL ROADS: During the life of the pit a haul road must be maintained for access. HAUL ROAD - SPIRAL SYSTEM: Haul road is arranged spirally along the perimeter walls of the pit. Terminology

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9 HAUL ROAD – SWITCH BACK SYSTEM: Zigzag pattern on one side of the pit. HAUL ROAD WIDTH: Function of capacity of the road and the size of the equipment. Haul road width must be considered in the overall pit design. Terminology

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10 Haul Road Effect on Pit Limits

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11 ANGLE OF REPOSE: Maximum slope of the broken material. SUBCROP OR ORE DEPTH: Depth of waste removed to reach initial ore. PRE-PRODUCTION STRIPPING: Stripping done to reach initial ore. Terminology

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12 ULTIMATE PIT LIMITS: Vertical and lateral extend of the economically mineable pit boundary. Determined on the basis of cost of removing overburden or waste material vs. the mineable value of the ore. PIT SCHEDULING: Material may be mined from the pit either in: sequential push backs conventional push backs. Terminology

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STRIPPING RATIO: Expressed in tons of waste to tons of ore in hard rock open pit operations. Critical and important parameter in pit design and scheduling. AVERAGE STRIP RATIO: Total waste divided by total ore within the ultimate pit. CUTOFF STRIPPING RATIO: Costs of mining a ton of ore and associated waste equals to net revenue from the ton of Ore. Terminology

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14 Single Working Bench

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15 Shovel in Working Bench

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16 Two Working Benches

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17 Final Pit Limit

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18 Example Mine 2001 2007 2011

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21 Pit Sequence (1)

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22 Pit Sequence (2)

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23 Pit Sequence (3)

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24 Pit Sequence (4)

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25 Section of Pit Sequence

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25 Thanks