Opencast Mining — Part 1 MCQs with Explanations

Stripper shovels are mostly deployed for Overburden removal in surface mining operations. Stripper shovels are large excavation machines used in open-pit mining, and they are designed specifically for removing overburden or waste rock from the surface to expose the underlying ore or mineral deposit. Option A, Coal mining, is a common application of stripper shovels as coal deposits are often located beneath thick layers of overburden material, which must be removed before the coal can be extracted. Option C, Hard rock mining, and Option D, Very hard rock mining, typically involve the use of other types of excavation equipment, such as drilling rigs, blasting equipment, and tunneling machines, that are better suited for the hard rock excavation. Therefore, the answer to this question is Option B, Overburden removal.

The correct answer is option A, Burden. Primary blasting is a technique used in mining and construction to break rock or concrete using explosives. The degree of fragmentation refers to the size and distribution of the pieces of rock or concrete after blasting. The burden is the distance between the explosive charge and the free face of the rock or concrete. By increasing the burden, the explosive energy is spread over a larger area, which can lead to a decrease in fragmentation. On the other hand, decreasing the burden concentrates the energy in a smaller area, resulting in increased fragmentation. Therefore, the correct way to increase the degree of fragmentation in primary blasting is to increase the special charge (the amount of explosive per unit length of the borehole) and decrease the burden. Option B, Spacing, refers to the distance between the boreholes and has an impact on the overall effectiveness of the blast, but not directly on the fragmentation. Option C, Height, refers to the depth of the borehole and has a minimal impact on fragmentation. Option D, Density, is not directly related to fragmentation, but it may affect the strength of the rock or concrete being blasted.

The injury rate per 1000 person employed can be calculated using the following formula: Injury rate = (Total number of injuries / Total number of persons employed) x 1000 Using the values given in the question, we can calculate the injury rate as follows: Injury rate = (16 / 800) x 1000 = 20 Therefore, the correct answer is option C, 20. The injury rate per 1000 person employed is a common metric used in occupational health and safety to measure the frequency of workplace injuries. The DGMS (Directorate General of Mines Safety) is a regulatory agency in India that sets safety standards and guidelines for the mining industry. As per DGMS norms, an injury rate of 20 or less is considered acceptable for opencast mines.

The open-cast mining method that eliminates drilling and blasting is the surface miner. Surface miners are machines that use a cutting drum to extract rock or minerals from the surface of the earth. They can selectively extract material without the need for drilling and blasting, which can reduce the environmental impact and improve safety. Option A, dozer, is a type of earthmoving equipment used for pushing soil, rocks, or other materials. Dozers are not typically used for extraction of minerals or rock. Option B, shovel, is a type of excavation equipment that uses a bucket to dig and load material. Shovels may require drilling and blasting to extract rock or minerals from the earth. Option C, dragline, is a large excavation machine that uses a bucket attached to a cable to dig and remove material. Draglines are often used in strip mining operations and may require drilling and blasting to extract rock or minerals from the earth. Therefore, the correct answer is option D, surface miner.

The limiting gradient of an ordinary vehicle is the steepest slope that it can climb without losing traction and slipping. The steepest slope that an ordinary vehicle can climb varies depending on several factors such as the weight, power, and tire type of the vehicle. However, as a general rule, the limiting gradient for an ordinary vehicle is approximately 1 in 6, which is option A in the given options. This means that for every 6 units of horizontal distance traveled, the vehicle can climb 1 unit of vertical distance without losing traction and slipping. It is important to note that the actual limiting gradient for a specific vehicle may vary depending on the specific conditions such as the type of surface, weather, and load of the vehicle. Therefore, it is essential to assess the specific conditions and consult the vehicle's manual to determine its actual limiting gradient.

The option that describes the use of heavy earthmoving machinery and well hole drills for mineral extraction is mechanized open-cast mining. Mechanized open-cast mining involves the use of heavy earthmoving machinery such as excavators, shovels, draglines, bulldozers, and dump trucks for the extraction of minerals from the surface of the earth. Well hole drills are also used to create blast holes for blasting activities in the mining process. Option A, manual mining, involves the use of manual labor to extract minerals from the earth. This method is labor-intensive and time-consuming and is usually used for small-scale mining operations. Option C, horizon, and option D, slicing, are not related to the extraction of minerals from the earth. Therefore, the correct answer is option B, mechanized open-cast mining.

The term R.M.R stands for Rockmass rating. Rockmass rating (RMR) is a widely used system for geomechanical classification of rocks in underground and surface mining. It is a numerical rating system that assesses the rock mass quality based on several parameters such as uniaxial compressive strength, rock quality designation, spacing of joints, groundwater conditions, and other factors. The RMR value ranges from 0 to 100 and is used to classify rock mass into five categories, ranging from very poor to excellent. The RMR system is an essential tool for predicting the stability of underground openings and designing support systems to ensure the safety of workers and equipment. Option A, rate of marginal return, option C, rating of massive roof, and option D, rated mass of rock, are not related to the geomechanical classification of rocks and the RMR system used in mining. Therefore, the correct answer is option B, rockmass rating.

The type of drill bit commonly employed in a wagon drill machine is the X' bit with tungsten carbide. Wagon drill machines are used for drilling blast holes in open-pit mining operations. These machines use high-pressure air to power the drill bit and are mounted on wheels or tracks for easy movement around the mining site. The X' bit with tungsten carbide is a hard and durable drill bit that can withstand the abrasiveness of rock surfaces encountered during drilling operations. Option A, auger bit, is commonly used for drilling holes in soil, whereas option D, worm bit, is used for drilling soft materials such as wood and plastics. Option B, eccentric bit, is not commonly used in mining operations. Therefore, the correct answer is option C, X' bit with tungsten carbide.

Option A: The grade of ore ultimately fed to the beneficiation plant This option is incorrect. While the cut-off grade can influence the grade of ore fed to the beneficiation plant, it specifically refers to the economic threshold below which mining is not profitable. Option B: Always the same average grade This option is incorrect. The cut-off grade is not always the same as the average grade. It is determined by economic factors and can vary depending on market conditions, costs, and other variables. Option C: The grade of ore through net the ore body This option is incorrect. The grade of ore through the ore body refers to the overall distribution of mineral content, but the cut-off grade specifically refers to the minimum grade at which mining becomes economically viable. Option D: The grade of ore below which mining is uneconomical This option is correct. The cut-off grade is the grade of ore below which mining operations are not economically feasible. It is a critical factor in determining whether a deposit can be profitably mined. Conclusion: The cut-off grade is the grade of ore below which mining is uneconomical, making Option D: The grade of ore below which mining is uneconomical the correct answer.

The correct answer to this question is D, Electric. Permanent and semi-permanent machines, such as electric shovels, drills, and haul trucks, are always powered by electricity. They are typically connected to the power supply system of the mine or a nearby substation through cables and conductors. Electric power is preferred over other types of power sources, such as diesel or kerosene, for several reasons. Electric power is cleaner, more efficient, and more economical than other types of power. Electric machines also produce less noise and air pollution, making them more environmentally friendly. Electric power can be generated from various sources, including coal, natural gas, nuclear, hydro, and renewable energy sources such as solar and wind power. The choice of power generation depends on several factors, including availability, cost, and environmental impact. Therefore, the correct answer is D, Electric.

The requirements of an electric power supply system in surface mines are: A. Adequate capacity: The power supply system must have sufficient capacity to meet the electrical demands of the mining equipment and facilities. B. Safe: The power supply system must be designed and maintained to ensure safe operation, with appropriate protections against electrical hazards. C. Required voltage and frequency: The power supply system must provide the voltage and frequency required by the mining equipment and facilities. D. Economical: The power supply system must be designed and operated in a cost-effective manner. Therefore, the answer to this question is Option E, All these.

A motor that improves power factor is a Synchronous motor (over excited). Power factor is the ratio of real power (measured in watts) to apparent power (measured in volt-amperes). A motor with a low power factor draws more current than is necessary to perform the desired work, which results in higher energy costs and lower system efficiency. By contrast, a synchronous motor with overexcitation can correct the power factor by adjusting the amount of reactive power that it draws from the power grid. Option A, Induction motor, and Option B, Slip ring motor, do not have the capability to adjust the power factor. Therefore, the answer to this question is Option C, Synchronous motor (over excited).

The diameter and depth of blast holes are generally kept constant depending on the size of equipment. In surface mining operations, the size of the equipment used for drilling blast holes determines the size of the blast holes that can be drilled. The diameter and depth of the blast holes must be sufficient to accommodate the explosive charge and ensure that the blast is effective in breaking up the rock mass. Option A, Base, Option C, Length, and Option D, Highwall, are not directly related to the size of the equipment used for drilling blast holes. Therefore, the answer to this question is Option B, Size.

Machines using crawler chains are not allowed to cross public roads if they possess Cleats or Grouser plates. Cleats or Grouser plates are metal protrusions that are mounted onto the crawler tracks of heavy machinery to provide better traction and stability on uneven surfaces. However, these plates can cause significant damage to public roads and are therefore not allowed for use on machines that need to cross public roads. Option B, Smooth grouser plates, and Option C, Plain plates without rubber, do not have protrusions that can cause damage to public roads and are therefore allowed to be used on machines that need to cross public roads. Therefore, the answer to this question is Option A, Cleats or Grouser plates.

A Ripper is essentially a crawler-mounted attachment used in surface mining and construction operations. The ripper attachment is designed to break up and loosen hard soil and rock, allowing for easier excavation and removal. Option A, Tyre, and Option C, Wheel, are not typically used for ripper attachments as they are not stable enough for heavy-duty excavation work. Therefore, the answer to this question is Option B, Crawler.

C.S.R stands for Corporate Social Responsibility. This refers to the concept that companies have a responsibility to operate in a way that benefits society, the environment, and the economy, while also maximizing profits. Corporate social responsibility involves taking into account the impact of a company's operations on the community, the environment, and other stakeholders, and working to minimize any negative effects and promote positive social and environmental outcomes. Option A, Company Survey Reportability, and Option C, Central Security Reason, are not related to the mining industry or corporate social responsibility. Therefore, the answer to this question is Option B, Corporate Social Responsibility.

Opencast mining is a surface mining technique where the overburden (the layer of rock and soil above the mineral deposit) is removed to expose the ore body. It's cost-effective for shallow deposits. Option A: Open cast Opencast mining becomes uneconomical at greater depths because the cost of removing the increasing volume of overburden outweighs the value of the extracted ore. The deeper the ore body, the more overburden needs to be excavated, transported, and disposed of, significantly increasing the cost. This makes it an uneconomical choice for deep deposits. Option B: Long wall Longwall mining is an underground mining method. It's used for extracting relatively flat, tabular deposits of coal or other minerals. Depth isn't the primary factor limiting its economic viability; rather factors such as geological conditions, roof stability, and the thickness and quality of the seam play a more significant role. Therefore, it is not inherently uneconomical at deeper depths compared to opencast. Option C: Bord and Pillar Bord and pillar is another underground mining technique where pillars of ore are left in place to support the roof. Again, the economic viability of this method is mostly determined by factors other than depth, though the costs associated with deeper shafts and haulage could eventually make it less profitable at extreme depths. Correct Answer: A The correct answer is Option A: Open cast because the costs associated with removing the progressively larger volume of overburden at increased depths render opencast mining uneconomical beyond a certain depth. Options B and C are underground methods and are not primarily limited by depth in the same way.

Diesel-powered excavators are heavy machinery used in opencast mining to excavate earth and rock. Their popularity stems from a combination of factors, primarily their power and reliability. Let's examine why option A is the best answer and address the others: Option A: Flexibility in operation: This is the most accurate answer. Diesel excavators offer significant operational flexibility. They are not tethered to power lines like electric excavators, allowing them to work across large, uneven mining sites without the constraint of power availability. This mobility and independence significantly improve productivity and efficiency in open-cast mining operations. They can be moved readily to different locations as needed, adapting to changing excavation requirements. Option B: Easy to operate: While modern excavators are generally designed with user-friendly controls, ease of operation is not the primary reason for their popularity. The complexity of operating heavy machinery remains significant, requiring skilled operators and extensive training. Option C: Handle oversized boulders: While diesel excavators are powerful and *can* handle some oversized boulders, this is not their defining characteristic. Specialized equipment like rock breakers or even blasting are often needed for extremely large or resistant rock formations. This capability is secondary to their overall operational flexibility and power. Option D: None: This is incorrect, as option A provides a compelling and accurate reason for the widespread use of diesel-powered excavators in open-cast mining.

Rest internal is the correct answer to “Blasting is always done during”. This question is standard in competitive examination syllabi for Opencast Mining.

Rifle bullet test is the correct answer to “Which test determines the sensitivity of explosive to shock and impact.”. This question is standard in competitive examination syllabi for Opencast Mining.

Long wall is the correct answer to “The mining method which does not distroy the land for agriculture and residential purposes.”. This question is standard in competitive examination syllabi for Opencast Mining.

3 to 4.5 is the correct answer to “The output capacity of a drag line with 23 to 30m 3 is million cu.m per year is”. This question is standard in competitive examination syllabi for Opencast Mining.

10 - 12t is the correct answer to “Yeild of coal per kg of special gelatine (60 - 80%) is generally in manual quarry.”. This question is standard in competitive examination syllabi for Opencast Mining.

Horizontal holes is the correct answer to “Drifters are generally designed to drill”. This question is standard in competitive examination syllabi for Opencast Mining.

Large is the correct answer to “Electric drive preferred for . . . . . . . . machines.”. This question is standard in competitive examination syllabi for Opencast Mining.

Floor and High wall is the correct answer to “The bench of open cast have two elements they are . . . . . . . . and . . . . . . . .”. This question is standard in competitive examination syllabi for Opencast Mining.

Slope stability rador is the correct answer to “Ensure safety in very deep open cast mine and at external dumps, instrumentation being done to record slope stability.”. This question is standard in competitive examination syllabi for Opencast Mining.

4 to 5 : 1 is the correct answer to “The stripping ratio for shavel dumper combination is . . . . . . . .”. This question is standard in competitive examination syllabi for Opencast Mining.

3m - 4.5m is the correct answer to “In manual quarry the bench, height usually in hard rock.”. This question is standard in competitive examination syllabi for Opencast Mining.

Max voltage of V 1.1 KV AC is the correct answer to “Shear needs electricity of”. This question is standard in competitive examination syllabi for Opencast Mining.

Linear tension is the correct answer to “Linear failure or plane failure is due to”. This question is standard in competitive examination syllabi for Opencast Mining.

State government is the correct answer to “The mining lease is granted by . . . . . . . .”. This question is standard in competitive examination syllabi for Opencast Mining.

1 in 10 is the correct answer to “Gradients of roads in quarries for tyred vehicular traffic should not exceed . . . . . . . .”. This question is standard in competitive examination syllabi for Opencast Mining.

7° is the correct answer to “The limiting gradient of surface miner.”. This question is standard in competitive examination syllabi for Opencast Mining.

Pull shovel is the correct answer to “The shovel used stripping top soil and making shallow cuts and benches upto depth of 3 - 6m is . . . . . . . .”. This question is standard in competitive examination syllabi for Opencast Mining.

Surface mining is the correct answer to “In which mining early extraction is possible with quick return.”. This question is standard in competitive examination syllabi for Opencast Mining.

Ripper and scraper dozer combination is the correct answer to “Where the over burden consists of soft rock which can be conveniently removed by”. This question is standard in competitive examination syllabi for Opencast Mining.

200 is the correct answer to “The flow rate of water in hydraulic mining for coal should be atleast a gallen per minute given by”. This question is standard in competitive examination syllabi for Opencast Mining.

30 - 37mm is the correct answer to “Hole dia meter of Jack hammer drill varies from”. This question is standard in competitive examination syllabi for Opencast Mining.

Good spell ability is the correct answer to “Jet piercing is suitable only for rocks.”. This question is standard in competitive examination syllabi for Opencast Mining.