JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B. Tech IV Year UNDERGROUND METAL MINING TECHNOLOGY Previous Question Paper (February/March - 2022 - R18)

Stoping methods are primarily classified based on the support mechanism employed to maintain the stability of the stope and the surrounding rock mass. The main categories are:

1. Unsupported Stoping Methods: These rely on the inherent strength of the ore and host rock. Examples include open stoping, sublevel stoping, and shrinkage stoping. These are suitable for strong, competent rock masses.
2. Supported Stoping Methods: These require artificial support to maintain stability. This includes cut-and-fill stoping, where waste material or tailings are used as fill, and square-set stoping, which utilizes timber or steel sets.
3. Caving Methods: These methods induce the collapse of the hanging wall or the ore body itself to facilitate mining. Examples include sublevel caving and block caving. These are typically used for large, low-grade deposits where surface subsidence is acceptable.

Metalliferous deposits exhibit distinct characteristics that dictate the choice of mining method and economic viability. Key characteristics include:

1. Mode of Occurrence: Deposits may occur as veins, lodes, pipes, or massive tabular bodies. The geometry (dip, strike, and thickness) significantly influences the layout of development workings.
2. Physical Properties: The strength, hardness, and abrasiveness of both the ore and the host rock determine drilling and blasting parameters, as well as the need for ground support.
3. Grade and Distribution: Metalliferous deposits are often heterogeneous. The distribution of valuable minerals (nugget effect or uniform dissemination) affects the selectivity of the mining method.
4. Depth and Geological Structure: Depth impacts the magnitude of in-situ stresses, while geological features like faults, joints, and folds can create instability, necessitating specific support strategies.
5. Hydrogeological Conditions: The presence of groundwater significantly influences safety, pumping requirements, and the stability of the rock mass, often requiring dewatering or grouting programs.
6. Economic Value: The cut-off grade is dynamic, depending on market prices, extraction costs, and processing efficiency, which ultimately defines the mineable limits of the deposit.