Mine Development And Mining Methods - Study Mode

[#71] What is the typical use of a "boxhole" in underground mining?
Correct Answer

(B) Raise driven upward for loading

Explanation

Solution: Boxhole Definition: A boxhole in underground mining is a small, typically rectangular, opening or chamber excavated from a larger mine opening (like a level or drift). It's specifically designed for a particular purpose related to material handling or access. Correct Answer: Option B: Raise driven upward for loading Boxholes are commonly used as the bottom loading point for raises. A raise is an inclined or vertical shaft driven upwards from a lower level to a higher level in a mine. The boxhole provides a convenient and controlled location to load broken ore or rock from the raise into mine cars or other haulage equipment. Its relatively small size compared to the raise itself makes it easier to manage the loading process and minimize spillage. Why other options are incorrect: Option A: To store explosives Storing explosives requires much stricter safety regulations and specialized, well-ventilated storage areas, not a simple boxhole. Boxholes are not designed for the safe handling and storage of explosives. Option C: Air exhaust system Airflow in underground mines is managed by larger, more carefully designed ventilation systems, not small boxholes. Boxholes are too small and their locations aren't typically optimal for efficient ventilation. Option D: Drainage gallery Drainage galleries are larger, dedicated passages constructed specifically for collecting and channeling water away from the mine workings. A boxhole's size and design are not suitable for this purpose.

[#72] The inclination of a decline ramp is usually:
Correct Answer

(B) 5 - 9 degrees

Explanation

Solution: Decline Ramp Definition: A decline ramp is an inclined roadway or tunnel that provides access to underground mine workings. Unlike shafts which are near-vertical, decline ramps have a gentler slope, allowing for easier transportation of equipment and materials using vehicles. Correct Answer: Option B (5-9 degrees) The inclination of a decline ramp is typically kept shallow, usually between 5 and 9 degrees. This is because a steeper incline would: * Increase the risk of accidents during transportation of equipment and personnel. * Require more powerful and expensive vehicles to negotiate the steeper grade. * Lead to increased wear and tear on vehicles and braking systems. * Make ventilation more challenging. Why Other Options Are Incorrect: Option A (45 degrees): A 45-degree incline is far too steep for a decline ramp used for routine transportation of equipment and personnel. It would present significant safety and operational challenges. Option C (60-70 degrees): This incline is even steeper than 45 degrees and is practically unusable for decline ramps. This would only be suitable for specialized applications (that aren’t common for decline ramps). Option D (30-35 degrees): While less steep than options A and C, this is still considered too steep for most decline ramps. It would still increase the challenges of equipment transportation and safety.

[#73] In vertical shaft sinking, what is a "collar"?
Correct Answer

(B) Opening of the shaft at surface

Explanation

Solution: Collar is the surface opening of a vertical shaft.The correct answer is: Opening of the shaft at surfaceIt requires strong reinforcement to prevent collapse and erosion.Usually supported by concrete or steel structures.

[#74] What is the main disadvantage of block caving?
Correct Answer

(B) High ore dilution

Explanation

Solution: Ore dilution is the major concern in block caving.The correct answer is: High ore dilutionAs the rock caves, waste rock can mix with ore, reducing grade.Though cost-effective for large volumes, it lacks selectivity.

[#75] Which technique is used to measure rock stability in underground openings?
Correct Answer

(C) Rock mass rating (RMR)

Explanation

Solution: RMR (Rock Mass Rating) classifies the quality of rock mass.The correct answer is: Rock mass rating (RMR)It evaluates rock joints, strength, groundwater, and orientation.Helps in selecting support systems and mining methods.