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

strong>Shaft sinking is the process of creating a vertical or inclined opening in the ground, typically for mining purposes.

The question asks about the major challenge in shaft sinking specifically in water-bearing strata. Water-bearing strata refers to geological layers of rock or soil that contain significant amounts of groundwater.

Option C: Water inflow and pressure is the correct answer. In water-bearing strata, the primary challenge during shaft sinking is the substantial inflow of water under pressure. This water can significantly hinder the sinking process in several ways:

* It can destabilize the shaft walls, leading to collapses.
* It can create difficulties in excavation and the removal of excavated material.
* It requires specialized and expensive equipment and methods for water control (e.g., freezing, grouting, compressed air).
* It poses significant safety risks to the workers.

Option A: Hard rock cutting is a challenge in shaft sinking, but it is not the *major* challenge in water-bearing strata. Hard rock presents difficulties in excavation, but it doesn't present the same level of immediate danger and operational disruption as a high-pressure water inflow.

Option B: Air quality control is important for worker safety in any underground mining operation, but it's not the *primary* problem associated with water-bearing strata. While managing dust and ventilation is crucial, water inflow presents a more direct and potentially catastrophic risk.

Option D: Crew safety training is essential for all mining operations, including shaft sinking. However, it's not a *challenge* inherent to water-bearing strata itself; rather, it's a crucial element in mitigating the challenges posed by water inflow (and other hazards). Water inflow presents the inherent geological and engineering challenge.

First, let's define some key terms:
Stope: A stope is an underground excavation where ore is extracted. It's essentially the working area of an underground mine.
Ore: Ore is a naturally occurring rock or sediment that contains sufficient concentrations of valuable minerals to be economically extracted.
Waste: Waste refers to the rock material in a mine that does not contain economically valuable minerals and is therefore left in place.

Now, let's look at the options:
Option A: Footwall
The footwall is the rock mass underlying an orebody or a fault plane. It is not necessarily a horizontal plane defining the separation between ore and waste in a stope.
Option B: Hanging wall
The hanging wall is the rock mass overlying an orebody or a fault plane. Similar to the footwall, it isn't specifically the horizontal plane separating ore and waste within a stope.
Option C: Ore-waste interface
The ore-waste interface is precisely the boundary, usually represented as a plane, that divides the ore from the waste rock within the stope. This is the accurate definition for the horizontal plane separating ore and waste in a stope.
Option D: Level drift
A level drift is a horizontal or nearly horizontal tunnel driven in a mine. It is a passageway, not the boundary between ore and waste.

Therefore, the correct answer is C. Ore-waste interface because it directly and accurately describes the horizontal plane separating the valuable ore from the waste rock within the stope.

Horizontal development, such as driving tunnels into a hillside, often precedes vertical development (sinking shafts) because it provides crucial access to the orebody. Tunnels allow for easier and safer transportation of equipment, personnel, and mined materials.

Furthermore, horizontal development enables early establishment of drainage systems. Water accumulation in underground mines can be a major safety and operational hazard. Establishing drainage channels and sumps horizontally allows for more controlled and effective water management before extensive vertical workings are created, preventing water from rushing down shafts and flooding deeper levels.

Why other options are incorrect:

Option A: Easier blasting: While blasting might be simpler in some horizontal situations, it's not the primary reason for prioritizing horizontal over vertical development. Blasting techniques are adaptable to both horizontal and vertical environments.

Option B: Faster machinery deployment: Machinery deployment is facilitated by access, which is a consequence of horizontal development, but not the main driving factor in the sequencing decision.

Option D: Lower equipment cost: Equipment costs can vary based on the specific mining method and geological conditions, but aren't fundamentally different between horizontal and vertical development to a significant enough degree to justify the choice. The costs are often comparable, and access provided by horizontal developments often allows for safer, more efficient equipment use, indirectly lowering overall costs in the long run.

Rock breaker is a hydraulic hammer mounted on an arm.The correct answer is: Rock breakerIt breaks oversize rocks stuck at grizzlies or drawpoints.Prevents delays in ore flow.

Staging chamber is a widened section in a shaft for loading/unloading personnel or materials.The correct answer is: Hoist changeover pointUsed to transfer between cage systems or rest zones.Also allows equipment maneuvering.

Shrinkage stoping is ideal for steep, narrow veins.The correct answer is: Shrinkage stopingBroken ore supports the stope until most of it is extracted.Requires strong ore and host rock.

Shaft collar is a reinforced structure at the surface opening.The correct answer is: Provide stable top for equipmentSupports hoisting structures and prevents surface collapse.Often constructed with concrete.

LHDs are compact, versatile loaders used in underground mines.The correct answer is: LHD (Load-Haul-Dump)They scoop, transport, and dump material efficiently in tight spaces.Battery, diesel, and electric versions are available.

Block caving is a bulk mining method with little control over what caves.The correct answer is: Block cavingOre and waste collapse together, leading to high dilution.Suitable only for low-grade, massive ore bodies.

Ramp is an inclined tunnel connecting levels.The correct answer is: Inclined access constructionUsed for vehicle access and ore haulage.Replaces vertical shafts in some mines.