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Introduction to Opencast Mining

Hello! Minners today we are going to discuss about Introduction to Opencast Mining

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Classification of Surface Mining Methods

Surface mining methods can be classified into two categories: open-pit mining and strip mining.

Open-pit mining involves extracting minerals from an open pit. This is done by removing the overburden (the soil and rock covering the mineral deposit) and then blasting and removing the ore. This method is typically used for extracting metals such as copper and gold, as well as other minerals such as coal and diamonds.

Strip mining involves removing a strip of overburden in order to extract the mineral deposit. This method is typically used for extracting coal and other minerals that are found near the surface. The overburden is removed in strips, and the mineral deposit is extracted in a similar manner to open-pit mining.

Another classification is Placer mining, a mining technique of extracting minerals from alluvial deposits and this is particularly used for precious metal like gold, tin and platinum.

Mountaintop Removal mining, a mining method that is used to extract coal that is found in mountainous regions. This method involves removing the top of a mountain in order to access the coal deposit beneath.
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What is an Opencast mine ?

Mining operation that is performed under the Sun Directly.

What is bench in opencast mining ?

In opencast mining, the horizontal layer is known as bench that reaches to the face.

Why does opencast mining is cheaper for companies ?

A lower stripping ratio means that less waste has to be removed to expose the ore for mining which generally results in a lower operating cost.

Factors affecting choice of Opencast Mining methods

There are several factors that can affect the choice of opencast mining method, including:

  1. Type of mineral deposit: The type of mineral deposit being mined can affect the choice of mining method. For example, hard rock deposits may require drilling and blasting, while softer deposits may be able to be mined using a dragline or shovel and truck method.
  2. Depth of deposit: The depth of the mineral deposit can also affect the choice of mining method. Shallow deposits can be mined using surface mining methods, while deeper deposits may require underground mining methods.
  3. Geology of the deposit: The geology of the deposit, including the type of rock, structure, and mineralogy, can also affect the choice of mining method.
  4. Mine size: The size of the mine can also affect the choice of mining method. Larger mines may require larger and more expensive equipment, while smaller mines may be able to use smaller and less expensive equipment.
  5. Environmental impact: The environmental impact of the mining method should also be considered. Surface mining methods can have a significant impact on the surrounding area, including deforestation, soil erosion, and water pollution.
  6. Economic factors: The cost of mining, equipment, and labor, as well as the expected revenue from the mineral deposit, can also affect the choice of mining method.
  7. Social factors: The impact of the mining on the local community, such as displacement of people, loss of livelihoods, and air and water pollution, also play a crucial role in the choice of mining method.


Advantages of Opencast Mining

Opencast mining, also known as open-pit mining or strip mining, has several advantages over other mining methods, including:

  • Accessibility: Opencast mining allows for easy access to the mineral deposit, making it possible to extract large amounts of ore in a relatively short amount of time.
  • Cost-effective: Opencast mining is generally more cost-effective than underground mining, as it requires less expensive equipment and infrastructure.
  • High production rate: Opencast mining has a high production rate, making it possible to extract large amounts of ore in a relatively short amount of time.
  • Safety: Opencast mining is generally considered to be safer than underground mining, as it allows for better ventilation and easier escape routes in case of an emergency.
  • Flexibility: Opencast mining can be adapted to different types of mineral deposits and mining conditions, allowing for a high degree of flexibility in mining operations.
  • Reclamation and Rehabilitation: Large area of land can be reclaimed and rehabilitated after mining, and can be used for other activities like agriculture and forestry.
  • Job creation: Opencast mining creates jobs in the areas of mining, transportation, and processing, which can have a positive economic impact on the surrounding communities.

It is worth noting that the benefits of opencast mining are also dependent on the environmental and social impact of the mining operation.

Disadvantages of Opencast Mining

Opencast mining, also known as open-pit mining or strip mining, has several disadvantages, including:

  • Environmental impact: Opencast mining can have a significant impact on the environment, including deforestation, soil erosion, and water pollution. It can also lead to the destruction of habitats and loss of biodiversity.
  • Displacement of people: Opencast mining can lead to the displacement of local communities and loss of livelihoods, as well as cultural heritage sites.
  • Dust and noise pollution: Opencast mining can lead to dust and noise pollution, which can have negative health effects on local communities and wildlife.
  • Safety hazards: Opencast mining can also pose safety hazards, including risks of landslides, rockfalls, and flooding.
  • High water usage: Opencast mining can require large amounts of water, which can be a problem in areas where water is scarce.
  • Long-term land degradation: After the mining is finished, large areas of land can be left degraded, making it difficult to reclaim and rehabilitate the land for other uses.
  • Surface subsidence: Surface subsidence may occur, caused by the removal of minerals from the earth, which can lead to structural damage to buildings and infrastructure.
  • High energy consumption: The mining process requires a lot of energy, and it can have a significant environmental impact in terms of carbon emissions and air pollution.

Stripping Ratio

The stripping ratio, also known as the "strip ratio" or "S:R ratio," is a measure of the amount of waste material (overburden) that must be removed in order to extract a given amount of ore. It is typically expressed as a ratio of the amount of waste material to the amount of ore. For example, a stripping ratio of 3:1 means that for every 3 cubic meters of waste material that is removed, 1 cubic meter of ore is extracted.

The stripping ratio is an important factor in the economics of open-pit mining. A lower stripping ratio means that less waste material needs to be removed to extract a given amount of ore, which makes the mining operation more cost-effective. On the other hand, a higher stripping ratio means that more waste material needs to be removed, which increases the cost of the mining operation.

The stripping ratio can vary depending on the mining method used, the size of the mining operation, and the location of the mineral deposit. It can also be affected by factors such as the type of mineral deposit, the geology of the deposit, and the mining equipment available.

The Stripping ratio is a very important factor, as it determines the profitability of a mining project. It is used to evaluate the size and scale of a mining project and to determine if it is economically viable. A low stripping ratio is more favorable for mining projects as it reduces the amount of overburden that needs to be removed, which in turn reduces the mining costs.
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Maximum allowable Stripping ratio


The maximum allowable stripping ratio, also known as the "break-even stripping ratio," is the highest stripping ratio at which a mining operation can still be economically viable. It is the point at which the cost of removing the overburden (waste material) equals the revenue generated from the extracted ore. Beyond this point, the mining operation would no longer be economically viable, as the cost of removing the overburden would be greater than the revenue generated from the ore.

The maximum allowable stripping ratio can vary depending on a number of factors, including the type of mineral deposit, the price of the ore, the cost of mining equipment and labor, and the cost of removing the overburden.

It's worth noting that, the maximum allowable stripping ratio is not a fixed value and can change depending on the fluctuating market conditions and mining costs. The mining companies continuously monitor the mining costs and ore prices and decide the maximum allowable stripping ratio accordingly.

In general, a low maximum allowable stripping ratio is more favorable for mining operations, as it allows for a higher percentage of ore to be extracted while keeping the mining costs low. Therefore, mining companies will try to maximize the ore recovery while keeping the stripping ratio as low as possible.


Overall Stripping Ratio


The overall stripping ratio, also known as the "lifetime stripping ratio" or "cumulative stripping ratio," is a measure of the total amount of waste material (overburden) that will be removed over the entire life of a mining operation. It is calculated by summing up the amount of waste material removed each year, and dividing that by the total amount of ore extracted over the same period.

The overall stripping ratio is an important factor in the long-term planning and management of a mining operation, as it gives an indication of the total amount of waste material that will need to be removed, and the impact that the mining operation will have on the environment.

The overall stripping ratio is determined by the mining plan, which is developed based on the mineral deposit, the mining method, and the mining equipment available. The mining plan will consider factors such as the type of mineral deposit, the location of the deposit, the geology of the deposit, the mining costs and expected revenue, as well as the social and environmental impact of the mining operation.

It is important to note that the overall stripping ratio is not a fixed value and it can change over time as mining progresses, as the mining plan can be modified based on the changing mining conditions, ore prices, and mining costs.

The overall stripping ratio can also be influenced by the mining method used, and some methods are more efficient in terms of waste removal and ore recovery. In general, a lower overall stripping ratio is more favorable for mining operations, as it reduces the total amount of waste material that needs to be removed, which in turn reduces the environmental impact of the mining operation and mining costs.

Break even stripping ratio


The break-even stripping ratio, also known as the "minimum stripping ratio" or "threshold stripping ratio," is the minimum ratio at which the income generated by the sale of the ore is equal to the costs of mining, including the cost of removing the overburden (waste material). It is the point at which the mining operation becomes economically viable, and the mining company starts to make a profit.

The break-even stripping ratio is typically determined by the mining company based on the expected costs of mining and the expected revenue from the sale of the ore. It can be affected by a number of factors, including the type of mineral deposit, the location of the deposit, the geology of the deposit, the mining costs, the ore prices, and the mining method used.

It is worth noting that the break-even stripping ratio is not a fixed value and it can change over time as mining progresses, as the mining plan can be modified based on the changing mining conditions, ore prices, and mining costs.

The break-even stripping ratio is an important factor in the feasibility and profitability of a mining project. If the actual stripping ratio is higher than the break-even ratio, the project will not be profitable and will not be carried out.

It is also important to note that the break-even stripping ratio should not only be based on financial considerations but also on the environmental and social impact of the mining operation. The mining companies should consider the impact of the mining on the local communities and the environment and set a break-even stripping ratio that is not only financially viable but also socially and environmentally sustainable.

Benches parameters


Height of the Bench 

In opencast mining, the height of the bench refers to the vertical height of the excavation face, or "bench," that is created during the mining process. The bench height is typically measured from the base of the excavation to the top of the bench.

The bench height is an important factor in the mining process, as it affects the amount of ore that can be extracted and the size of the equipment that can be used. A higher bench height allows for larger equipment to be used, which can result in a higher production rate. However, a higher bench height also requires more overburden (waste material) to be removed, which can increase the cost of the mining operation.

The bench height is determined by the mining company based on a number of factors, including the type of mineral deposit, the location of the deposit, the geology of the deposit, the mining costs, the ore prices, and the mining method used. The bench height is also determined by the mining equipment available and the safety and stability of the excavation face.

It is worth noting that the bench height is not a fixed value and it can change over time as mining progresses, as the mining plan can be modified based on the changing mining conditions, ore prices, and mining costs.

In general, a lower bench height is more favorable for mining operations, as it reduces the amount of overburden that needs to be removed and the environmental impact of the mining operation. However, the bench height should be balanced with the need to increase the production rate, equipment size and safety considerations.

Width of the Bench

In opencast mining, the width of the bench refers to the horizontal width of the excavation face, or "bench," that is created during the mining process. The width of the bench is typically measured from the toe of the bench to the crest of the bench.

The width of the bench is an important factor in the mining process, as it affects the amount of ore that can be extracted, the stability of the excavation face, and the safety of the mining operation. A wider bench allows for more ore to be extracted, but it also requires more overburden (waste material) to be removed and can increase the cost of the mining operation. A narrower bench can be safer and more stable but can also reduce the production rate.

The width of the bench is determined by the mining company based on a number of factors, including the type of mineral deposit, the location of the deposit, the geology of the deposit, the mining costs, the ore prices, and the mining method used. The width of the bench is also determined by the mining equipment available and the safety and stability of the excavation face.

It is worth noting that the width of the bench is not a fixed value and it can change over time as mining progresses, as the mining plan can be modified based on the changing mining conditions, ore prices, and mining costs.

In general, a balance between the width of the bench, mining production rate, mining costs, safety considerations, and environmental impact is considered while determining the width of the bench. The mining company will consider all of these factors and make adjustments as necessary to optimize the mining process.

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