Mine Development And Mining Methods - Study Mode

[#131] What is the primary purpose of a boxhole in mining?
Correct Answer

(D) Explosive charging

Explanation

Solution: Definition of Boxhole: A boxhole in mining is a short, upward-driven raise or excavation typically created from a lower level toward an upper area in underground mining. It is a narrow and steeply inclined or vertical opening used for specific operational tasks in confined or controlled spaces. Correct Answer: Option D: Explosive charging The primary purpose of a boxhole is to serve as a safe and controlled location for loading explosives in blasting operations. Boxholes allow miners to insert and position explosives precisely into the rock mass, which is critical for achieving effective and targeted rock breakage. Boxholes are strategically placed to ensure that the blast energy is directed in the intended direction, and they provide a degree of protection for personnel by isolating them from direct exposure to the blast area. Their compact and enclosed design also helps in minimizing risks associated with misfires or fly rock in underground environments. Explanation of Other Options: Option A: Dewatering Dewatering involves removing water from the mine using pumps and drainage systems. While water may occasionally drain through a boxhole due to gravity, it is not designed or used primarily for dewatering purposes. Option B: Horizontal ventilation Ventilation systems in mines include dedicated airways, raises, and fans that manage airflow across the entire mine. A boxhole, being vertical and small, does not play a role in horizontal ventilation . Option C: Ore transfer upward Ore transfer is usually carried out using larger infrastructure such as ore passes, vertical shafts, conveyors, or skips. A boxhole is too small and structurally unsuitable for regular ore transport in an upward direction. Conclusion: Thus, the correct answer is Option D: Explosive charging , as boxholes are specifically constructed to support the safe, effective, and controlled placement of explosives in underground mining operations.

[#132] What is an essential characteristic of a sublevel caving method?
Correct Answer

(C) Controlled collapse of overlying rock

Explanation

Solution: Definition of Sublevel Caving: Sublevel caving is an underground mining method in which ore is fragmented by drilling and blasting on multiple levels (sublevels) situated between the main levels of the mine. After blasting, the broken ore is drawn off from below, and the overlying rock mass is allowed to collapse into the void created. This method is used primarily in massive ore bodies where the ore and host rock are weak to moderately strong. Correct Answer: Option C: Controlled collapse of overlying rock An essential characteristic of sublevel caving is the controlled collapse of the overlying rock as ore is extracted. As ore is drawn out from below, the surrounding waste rock from the hanging wall caves in to fill the void. This controlled caving process is intentional and designed to follow the retreat of the mining front. The success of sublevel caving relies on managing this collapse effectively. The caving of overburden provides a continuous source of broken material, maintaining productivity while minimizing the need for backfilling. However, dilution from the waste rock is a key challenge that must be managed carefully. Explanation of Other Options: Option A: Entire stope is backfilled immediately This is characteristic of methods like cut-and-fill mining. In sublevel caving, backfilling is typically not done immediately or extensively , as the voids are filled naturally by caved-in waste rock. Option B: Ore is extracted with minimal waste Sublevel caving usually involves some degree of waste rock mixing with ore (dilution) due to the caving process. Therefore, it does not guarantee minimal waste compared to methods like room-and-pillar or cut-and-fill mining. Option D: Manual drilling is not required While modern sublevel caving operations use mechanized drilling, the statement is misleading. Drilling is a critical component of the method, and in some cases, manual drilling may still be required depending on conditions. Conclusion: The correct answer is Option C: Controlled collapse of overlying rock , as this feature defines the core operational principle of sublevel caving and distinguishes it from other underground mining methods.

[#133] Which underground opening is developed first in most mining operations?
Correct Answer

(B) Adit

Explanation

Solution: Underground Opening Development in Mining: Before explaining the answer, let's define some key terms: Stope: A stope is the underground excavation where ore is extracted. It's essentially the working area of the mine. Adit: An adit is a horizontal or nearly horizontal passage from the surface into a mine. It provides access to the mine without the need for deep vertical shafts. Shaft: A shaft is a vertical or steeply inclined opening from the surface to underground workings. It's used for access, ventilation, and hoisting ore and personnel. Raise: A raise is a typically vertical or steeply inclined opening excavated from below upwards. It's often used to connect different underground levels. Correct Answer: B - Adit In most mining operations, an adit is developed first. This is because an adit offers several advantages: It provides relatively inexpensive and easy access to the ore body, especially if the ore body is located at a shallow depth or on a hillside. It minimizes the need for extensive and costly shaft sinking. It can facilitate early exploration and development of the ore body. Why other options are less likely to be developed first: A - Stope: Stopes are developed *after* access to the ore body has been established. You can't extract ore until you can get to it. C - Shaft: Shafts are more expensive and time-consuming to construct than adits. They're generally used when the ore body is too deep to access easily via an adit or when large volumes of ore need to be extracted. D - Raise: Raises are typically used to connect different levels *within* the mine after initial access has been gained. They're not the primary access point.

[#134] In which scenario is twin shaft system preferred?
Correct Answer

(C) Deep mining with high hoisting needs

Explanation

Solution: Twin shaft system involves separate shafts for man/material and ore hoisting.The correct answer is: Deep mining with high hoisting needsImproves efficiency and safety in large operations.Used in major metal mines globally.

[#135] What is the main concern when driving headings in swelling ground?
Correct Answer

(C) Ground pressure and convergence

Explanation

Solution: Swelling ground expands upon exposure to air or water.The correct answer is: Ground pressure and convergenceThis can squeeze supports and close tunnels.Requires strong supports and regular re-bolting.