Opencast Mining MCQs Questions & Answers | Mining Engineering

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.