Questions
12 questions per paper
Difficulty
Medium-Hard
Importance
High yield for HPCL/NTPC/ONGC
Overview
Mining Methods and Machinery cover the essential techniques for extracting mineral resources and the heavy equipment required to facilitate these operations. This topic is critical for PSU exams as it forms the technical foundation for operations in the energy and raw material sectors. Aspirants must master the distinctions between surface and underground extraction strategies and their associated mechanical deployments.
Surface Mining: Open Cast and Strip
Surface mining involves removing overburden to expose minerals, making it the most cost-effective method for shallow deposits. Exams frequently test on the sequence of operations, including drilling, blasting, loading, and hauling.
- Open cast mining uses a bench system to maintain slope stability.
- Strip mining is primarily used for horizontal deposits like coal seams.
- Overburden-to-coal ratio is a critical economic indicator.
- Bench height is determined by the reach of the loading equipment.
Underground Mining: Room & Pillar and Longwall
These methods are employed when the depth of the deposit makes surface mining unfeasible. Room and Pillar creates a grid-like structure for stability, while Longwall mining facilitates total extraction of high-value seams using automated roof supports.
- Room and Pillar uses pillars left in situ to support the overburden.
- Longwall mining uses a Shearer to cut coal and hydraulic powered roof supports.
- Subsidence control is a major design consideration for underground stability.
- Longwall provides higher safety levels compared to Room and Pillar due to mechanization.
Mining Machinery: Loaders, Dumpers, and Miners
The productivity of a mine relies heavily on the efficient matching of hauling and loading cycles. Candidates must understand the operational capacity and the specific application environment for each machine type.
- Continuous Miners eliminate the need for drilling and blasting in soft to medium rock.
- Rear dumpers are standard for open-cast haulage due to maneuverability.
- Shovel-dumper matching is a core optimization problem for production scheduling.
- LHD (Load-Haul-Dump) machines are standard for underground extraction.
Shaft Sinking and Stoping
Shaft sinking provides the primary access to deep underground reserves, while stoping refers to the actual ore extraction sequence. These topics often feature in descriptive or memory-based questions regarding terminology.
- Shaft sinking methods include Full-face method and Bench method.
- Shrinkage stoping uses broken ore as a working platform.
- Cut and fill stoping is preferred for weak wall rocks.
- VCR (Vertical Crater Retreat) relies on large diameter blastholes.
Formula Sheet
Stripping Ratio = Total Volume of Overburden / Total Volume of Ore
Production Rate = (Bucket Capacity * Fill Factor * Cycles per hour) / Time
Tonnage of Coal = Area * Thickness * Density
Exam Tip
Focus on the 'Suitability Criteria' for each mining method, as PSUs love asking which method is best for specific geological conditions like seam thickness or dip angle.
Common Mistakes
- Confusing the specific applications of Longwall vs. Room and Pillar mining in coal seams.
- Neglecting the impact of bench height and slope angle on overall mine safety parameters.
- Failing to distinguish between production equipment (Continuous Miners) and transport equipment (Dumpers).
More Revision Notes
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