JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III SURFACE MINING TECHNOLOGY Previous Question Paper (November/December - 2020 - R16)

The selection between opencast (surface) mining and underground mining is a critical decision based on technical, economic, and safety parameters. The primary criteria include:

• Depth of Deposit: Opencast mining is generally preferred for shallow deposits where the stripping ratio (volume of overburden to be removed per unit of mineral) is economically viable. As depth increases, the cost of overburden removal rises, eventually favoring underground methods.
• Geological Conditions: The dip, thickness, and continuity of the ore body are decisive. Thick, massive, and shallow deposits are ideal for open-pit mining. Deep-seated, thin, or steeply dipping seams often necessitate underground extraction to avoid excessive waste removal.
• Economic Viability: A feasibility study is conducted to compare the Capital Expenditure (CAPEX) and Operating Expenditure (OPEX). Opencast mines typically have higher initial equipment costs but lower operating costs per tonne compared to the labor-intensive nature of underground mining.
• Safety and Environment: Surface mining is generally safer due to better ventilation and lower risk of strata failure. However, it has a larger surface footprint and higher environmental impact regarding noise, dust, and land degradation, which may influence regulatory approvals.
• Recovery Rates: Underground mining often allows for higher selectivity and recovery of high-grade ore, whereas opencast mining may result in higher dilution if not managed correctly.

The Mine Life Cycle represents the sequential phases a mining project undergoes from initial discovery to final closure. It consists of five distinct stages:

• Prospecting and Exploration: This initial phase involves geological mapping, geophysical surveys, and drilling to define the size, grade, and economic viability of the mineral deposit.
• Feasibility and Planning: Detailed engineering studies are conducted to determine the optimal mining method, infrastructure requirements, and Environmental Impact Assessment (EIA). Financial models are developed to secure investment.
• Development and Construction: This stage involves site preparation, building access roads, power supply, processing plants, and removing the initial overburden to access the ore body.
• Production (Operation): The core phase where the mineral is extracted, processed, and transported to the market. This stage involves continuous mine planning, safety management, and production optimization.
• Closure and Reclamation: The final phase, which includes decommissioning infrastructure, rehabilitating the land to a safe and stable state, and implementing long-term environmental monitoring to ensure the site is returned to a sustainable post-mining use.

Effective management of each phase is essential to ensure regulatory compliance and social license to operate throughout the project's life.