Mine Development and Mining Methods MCQs Questions & Answers | Mining Engineering

Definition:
Highly fractured ore bodies are ore deposits characterized by extensive fracturing and jointing, resulting in weak rock mass and potential instability.

Correct Answer: Sublevel Caving (A)
Sublevel caving is a method particularly well-suited for large, steeply dipping, and highly fractured ore bodies. This is because the method relies on the inherent instability of the fractured rock. The ore is extracted from sublevels, and the overlying ore is allowed to cave progressively. The fracturing facilitates this caving process, making it relatively easy to break down the ore and allowing for efficient extraction. The broken ore is drawn from the drawpoints at the bottom of the stopes.

Why other options are less suitable:
Shrinkage Stoping (B): While shrinkage stoping can handle some fracturing, it's less effective in highly fractured ground because the broken ore's self-supporting nature becomes unreliable in extremely fragmented conditions. Maintaining the stope walls becomes significantly more difficult, leading to instability and safety concerns.

Cut and Fill (C): Cut and fill requires relatively stable walls for effective operation. Highly fractured ore bodies lack this stability. The fill material would be lost into the fractures, rendering the method inefficient and potentially hazardous.

Room and Pillar (D): Room and pillar is suitable for relatively strong, less fractured ore bodies where pillars are left in place to support the roof. In highly fractured ore bodies, maintaining the integrity of the pillars would be challenging, leading to potential roof collapses and operational difficulties. The pillars would be weakened by the fracturing, rendering them ineffective for support.

Definition of Grouting:
Grouting is a technique used in mining and civil engineering to inject a fluid material—typically cement-based, chemical, or resin grout—into rock or soil to fill cracks, fissures, or voids. Once the material sets, it strengthens the ground and helps seal off pathways for water or gas infiltration.

Correct Answer: Option B: Reduce water inflow
The correct answer is Option B: Reduce water inflow because the main function of grouting in mine development is to seal water-bearing fractures and reduce or completely block the inflow of groundwater into the underground workings. This is crucial for maintaining safe, dry, and stable conditions during tunneling, shaft sinking, or excavation.

By controlling water ingress, grouting prevents potential flooding, minimizes the need for continuous pumping, and reduces the risk of ground instability caused by water pressure. It also makes drilling and blasting operations more effective and safer in saturated zones.

Grouting is often done ahead of development headings in advance of expected water-bearing zones or during shaft sinking in wet ground. The process enhances the structural integrity of the surrounding rock mass and ensures that construction can proceed efficiently and safely.

Explanation of Other Options:
Option A: Ore extraction
Ore extraction involves drilling, blasting, and transporting broken ore, not sealing fractures or water channels.

Option C: Explosive charging
Explosive charging is related to blasting operations and has no direct connection with the grouting process.

Option D: Increase ventilation
Ventilation is improved through the construction of airways and installation of fans—not by injecting grout into the rock.

Conclusion:
Therefore, the correct answer is Option B: Reduce water inflow, as grouting is primarily employed in mine development to control groundwater and improve ground stability by sealing water pathways.

Cut and Fill offers wall support by backfilling mined-out spaces.The correct answer is: Cut and FillIt protects weak hanging walls and allows selective mining.Useful when ore is competent and host rock is poor.

Drift is a horizontal passage driven in ore or waste.The correct answer is: A horizontal tunnelUsed for access, haulage, or development purposes.It runs parallel to the ore body or along the vein.

Ore body geometry refers to the shape, size, and orientation of the ore deposit within the earth.
Rock mechanics describes the physical and mechanical properties of the rocks surrounding and containing the ore body, including strength, stress, and fracturing.

Market price of ore is the economic value of the extracted ore, influencing the profitability of different mining methods.

The choice of mining method is a crucial decision in mining engineering, heavily influenced by various geological and economic factors.

Option A, Ore body geometry, significantly influences the choice of mining method. Different geometries (e.g., tabular, massive, disseminated) necessitate different approaches to extraction. A steeply dipping vein might require underground methods, while a flat-lying deposit may lend itself to surface mining.

Option B, Rock mechanics, are equally critical. The strength and stability of the surrounding rock determine whether open-pit or underground methods are feasible and safe. Weak rocks might necessitate support systems that alter the chosen method.

Option C, Market price of ore, is a major economic driver. If the ore price is high, more expensive and complex methods might be justified to extract all of the ore, even from challenging geometries or rock conditions. Conversely, a low ore price may necessitate simpler, less costly methods, focusing on higher-grade ore.

Option D, Color of ore, is irrelevant to the choice of mining method. The color of the ore has no bearing on the feasibility, safety, or economics of extraction. The physical properties and geological context of the deposit are far more significant.

Therefore, the correct answer is D: Color of ore because the color is an aesthetic property that has no impact on the engineering decisions related to mining methods.

Raise is a vertical or inclined opening driven upward from one level to another.The correct answer is: RaiseUsed for ventilation, ore transfer, and escape routes.Drift is horizontal, shaft is vertical from surface, and crosscut connects drifts.

Shrinkage Stoping is used for steep, thick ore bodies with strong rock.The correct answer is: Shrinkage StopingBroken ore is left in place to support the stope until most of the ore is extracted.Efficient when wall rock is stable and self-supporting.

Decline or ramp is an inclined tunnel used for vehicle access.The correct answer is: DeclineUsed for transporting equipment, ore, and personnel.Shafts are vertical; raises go upward; drifts are horizontal.

The term "back" in underground mining refers to the roof or ceiling of an excavation.

In simpler terms, when miners are working in an underground tunnel, drift, or stope, the "back" is the surface directly above them.

Therefore, the correct answer is Option C.

Let's look at why other options are incorrect:

Option A: The footwall of the stope - The footwall is the lower, relatively undisturbed side of a mineral vein or ore body. It's not the roof.

Option B: The sidewall of the tunnel - The sidewalls are the vertical surfaces on either side of a tunnel, not the top.

Option D: The pillar between rooms - Pillars are left-in-place ore or rock to support the overlying strata and prevent collapse. They are not the roof of an excavation.

Block Caving is the correct answer.

First, let's define Block Caving. Block caving is a bulk mining method used to extract large, relatively low-grade orebodies. It involves creating an undercut in the orebody, then intentionally inducing a controlled collapse of the ore to facilitate extraction from the bottom.

The process involves undercutting a large block of ore, usually from several levels, creating a void. The weight of the overlying ore then causes it to fracture and collapse into this void. The broken ore is then drawn off through draw points at the bottom of the caved block.

Now let's look at why the other options are incorrect:

Option A: Sublevel Stoping: Sublevel stoping involves mining ore in horizontal slices from multiple levels. The ore is broken using blasting and then removed. It does not involve artificially collapsing an entire orebody.

Option B: Cut and Fill: Cut and fill is a method where ore is extracted in slices. As each slice is mined, the void is filled with waste material (the "fill"). This is a controlled mining method that does not involve collapsing the ore.

Option D: Shrinkage Stoping: Shrinkage stoping is a method where ore is broken and then some of the broken ore is removed, leaving space for more ore to be broken. This space "shrinks" as more ore is removed. This also does not involve the artificial collapse of a large block of ore.

In summary, only block caving relies on the intentional and controlled collapse of a large orebody as the primary means of extraction.