Welcome back to our Longwall Mining MCQ series. In Part 1 we covered the basics: the equipment, the layout and the main terms. Part 2 goes a little deeper into how the system actually behaves: advancing versus retreating, roof behaviour, support mechanics, thick seam methods and the hazards you need to understand for exams and for the job.
There are 15 questions here (Q16 to Q30). Try each one before you tap Show Answer, and read the short explanation even when you get it right. That is where most of the learning happens.
Longwall Mining MCQs: Part 02 (Q16 to Q30)
16. What roles do the gate roads play in a longwall panel?
- A. They are used only for coal transport
- B. They are used only for ventilation
- C. They are used only for moving men and supplies
- D. All of these: coal, air and men and materials move through them
Show Answer
Answer: DGate roads are the working lifeline of a panel. Coal goes out, fresh air comes in and return air leaves, and people and materials travel through them.
17. Which is an advantage of the retreating longwall system over the advancing system?
- A. No gate roads are needed at all
- B. Gate roads are driven ahead, so conditions in the panel are known before extraction starts
- C. The panel cannot be ventilated properly
- D. Powered supports are not required
Show Answer
Answer: BIn the retreat system the gate roads are developed up to the panel boundary first, so faults and changes in the seam show up before the face is installed.
18. What does an advancing longwall mean?
- A. The face moves away from the shaft or main roadways, and the gate roads are formed as the face advances
- B. The face moves towards the shaft, with gate roads driven ahead
- C. The face works without any roof support
- D. It is another name for bord and pillar
Show Answer
Answer: AIn advancing longwall, extraction starts near the shaft or main roadways and moves outwards. The roads have to be formed and kept open behind the face, which makes it harder to maintain than the retreat system.
19. How is the caving of the roof behind the supports handled in longwall mining?
- A. It is strictly prevented
- B. It is left to chance without any monitoring
- C. It is allowed to occur in a controlled manner as the supports advance
- D. It is stopped by building timber chocks
Show Answer
Answer: CLongwall is a caving method. The supports hold up the roof over the face and walkway, and the roof behind them is allowed to fall in a controlled way.
20. Which gas is the main explosion hazard on a gassy longwall face?
- A. Methane
- B. Nitrogen
- C. Oxygen
- D. Carbon dioxide
Show Answer
Answer: AMethane (firedamp) is explosive within roughly 5 to 15 percent in air. That is why face ventilation, gas monitoring and gas drainage are so important.
21. What is meant by 'periodic weighting' on a longwall face?
- A. A weekly weighing of coal output
- B. Regular calibration of the shearer
- C. A cyclic rise in roof pressure when the main roof strata break and settle
- D. Weighing the supports before installation
Show Answer
Answer: CAs the face advances, the strong main roof breaks at fairly regular intervals. Each break briefly increases the load on the supports and the face.
22. Why are powered supports fitted with relief (yield) valves?
- A. To increase the pump speed
- B. To release fluid and prevent damage when the roof load exceeds the support's rated resistance
- C. To refill the support with fluid
- D. To cool the hydraulic fluid
Show Answer
Answer: BA yield valve opens when the load passes the set limit, so the support yields instead of being damaged, and then it closes and keeps holding.
23. How is a powered support moved forward to the new face line?
- A. It is pulled by a winch from the maingate
- B. It is pushed forward by workers
- C. It is dragged by the shearer
- D. It is lowered slightly and moved forward by its hydraulic advance ram, which reacts against the AFC, and then it is set again
Show Answer
Answer: DPowered supports are self-advancing. The ram connected to the AFC pushes or pulls the support forward after the roof has been released slightly, and the support is then re-set against the roof.
24. What is the beam stage loader (BSL) used for?
- A. Cutting coal at the tailgate
- B. Supporting the roof at the maingate
- C. Receiving coal from the AFC and passing it to the gate belt conveyor, often crushing oversize lumps
- D. Spraying water on the face
Show Answer
Answer: CThe BSL sits at the maingate end. It is the link between the face conveyor and the gate conveyor, and many units include a crusher.
25. How are the gate roads of a longwall panel commonly developed?
- A. By continuous miners or roadheaders
- B. By the shearer
- C. By a dragline
- D. By a bucket wheel excavator
Show Answer
Answer: AGate roads are roadways, so they are driven by roadway development machines such as continuous miners and roadheaders (or by other methods that suit the mine). The shearer works on the longwall face.
26. Which longwall variant is used for very thick seams?
- A. Bord and pillar
- B. Longwall top coal caving (LTCC)
- C. Opencast mining
- D. Room blasting
Show Answer
Answer: BIn LTCC, a shearer cuts the lower section of the seam, and the upper top coal caves and is drawn out through openings in the supports.
27. Which of the following is NOT an advantage of longwall mining?
- A. High output concentrated at one face
- B. High percentage of extraction
- C. Mechanised operation with fewer people exposed at the face
- D. Easy selective mining of different coal qualities
Show Answer
Answer: DLongwall takes the whole seam section in one go, so it is not a selective method. High output, high recovery and mechanisation are its strengths.
28. A large block of coal left to protect permanent roadways from the effects of longwall extraction is called:
- A. A barrier pillar
- B. A rib
- C. A prop
- D. A stowing pack
Show Answer
Answer: ABarrier pillars protect important structures such as shafts and main roadways. Chain pillars, by contrast, protect the gate roads between panels.
29. Compared with partial extraction methods, subsidence over a longwall panel is generally:
- A. Absent
- B. Greater, but more uniform and predictable
- C. Random and unpredictable
- D. Limited to the goaf only
Show Answer
Answer: BBecause the whole seam section is extracted, the surface above usually settles fully. The movement tends to follow a pattern, which is why subsidence can be predicted and planned for.
30. What is the main purpose of water sprays on a shearer?
- A. To make the coal wet for sale
- B. To lubricate the AFC
- C. To suppress dust and reduce the risk of frictional ignition
- D. To test the pump
Show Answer
Answer: CCutting coal creates dust and sparks. Sprays on the drums help control respirable dust and reduce the chance of frictional ignition of methane.
Answer key
| Q | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 |
|---|---|---|---|---|---|---|---|---|
| Ans | D | B | A | C | A | C | B | D |
| Q | 24 | 25 | 26 | 27 | 28 | 29 | 30 | |
| Ans | C | A | B | D | A | B | C |
Quick revision points from this set
- Retreat vs advance: in retreat, gate roads are developed first and the face comes back towards the main roadways. In advance, the face moves outwards and the roads are formed behind it.
- Roof behaviour: caving behind the supports is planned, and periodic weighting is the regular pressure rise when the main roof breaks.
- Supports: self-advancing, with yield valves to protect them from overload.
- Key equipment: shearer, AFC, beam stage loader, powered supports.
- Pillars: barrier pillars protect main roadways and shafts, and chain pillars protect gate roads between panels.
- Hazards: methane, dust, spontaneous heating in the goaf and sudden roof loading.
- Thick seams: longwall top coal caving (LTCC).
Note: these questions are for practice and revision. Terms and details can vary between textbooks and countries, so follow your syllabus. For statutory provisions on longwall working, refer to the Coal Mines Regulations and the latest DGMS circulars.
Longwall Mining MCQ Series
This series is designed to build a deeper understanding of longwall mining and to help with exam preparation.
Previous: Part 01 Next: Part 03
 || Indian Minerology ){kind=link}
0 Comments