Welcome to Part 4 of the Longwall Mining MCQ series. By now you know how a panel is laid out, how the machines work and how the roof behaves. This set goes after the topics that separate an average answer from a strong one: ground stress around the face, ventilation in gassy seams, hanging roofs, thick seam caving, dust, heat and automation.
If you have not seen the earlier parts, you can start with Part 1, Part 2 and Part 3. This set has 15 questions (Q46 to Q60). Try each before tapping Show Answer.
Longwall Mining MCQs: Part 04 (Q46 to Q60)
46. How are the gate roads of a longwall panel commonly supported?
- A. Powered supports
- B. Roof bolts, often supplemented with cable bolts or steel supports where needed
- C. Wooden chocks only
- D. No support at all
Show Answer
Answer: BGate roads must stay open for the whole life of the panel. Bolting is the usual primary support, with extra support in poor ground.
47. What is 'front abutment pressure' on a longwall face?
- A. The pressure of the hydraulic fluid
- B. The pressure of the ventilating air
- C. The load on the AFC chain
- D. The zone of increased vertical stress in the coal ahead of the face
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Answer: DAs coal is extracted, the load it used to carry is transferred to the solid coal ahead of the face. This raises the stress there and is one reason why coal at the face may spall.
48. What is 'side abutment' stress?
- A. Increased stress transferred to the solid coal and pillars beside a worked-out panel
- B. Stress in the floor only
- C. Stress caused by blasting
- D. Stress in the AFC chain
Show Answer
Answer: AGate roads next to a goaf feel this extra load. Chain pillars are designed to carry it and protect the roads.
49. What is the main benefit of a Y-type ventilation arrangement on a gassy longwall face?
- A. It removes the need for ventilation
- B. It makes the face hotter
- C. An extra roadway on the goaf side helps carry away goaf gas and keeps methane at the tailgate corner lower
- D. It reduces the number of supports needed
Show Answer
Answer: CIn a Y-system, an additional airway at the goaf side helps sweep gas away, which is useful in gassy seams where methane builds up at the tailgate end.
50. What is a major risk if a very strong main roof does not cave behind the supports?
- A. The shearer cuts faster
- B. A large unsupported span builds up and can break suddenly, causing heavy weighting and air blasts
- C. Methane disappears from the goaf
- D. The AFC needs less power
Show Answer
Answer: BA hanging roof stores energy. When it finally breaks, it can load the supports heavily and push air violently out of the goaf towards the face.
51. What is the rear conveyor behind the supports used for in Longwall Top Coal Caving (LTCC)?
- A. Carrying water to the face
- B. Carrying men
- C. Carrying roof bolts
- D. Carrying top coal that is drawn through the openings at the rear of the supports
Show Answer
Answer: DIn LTCC, the top coal caves behind the supports and is drawn out through a coal window. A second conveyor at the rear takes this coal away.
52. Which maintenance approach best reduces unplanned downtime on a longwall face?
- A. Repairing only after breakdowns
- B. Skipping inspections to save time
- C. Planned preventive maintenance with condition monitoring
- D. Ignoring oil and temperature trends
Show Answer
Answer: CA longwall works as a chain. When one machine stops, the whole face stops, so regular checks and monitoring of oil, temperature and vibration pay for themselves.
53. Why is the longwall face kept straight and square to the gate roads?
- A. To avoid uneven loading, support overlap and damage to the AFC
- B. To make the face look neat only
- C. To reduce dust to zero
- D. To help the roof cave faster
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Answer: AA skewed face makes the AFC and supports work against each other, which leads to damage, delays and poor roof control.
54. Where does most respirable dust on a longwall face come from?
- A. Blasting in the gate roads only
- B. The sump
- C. The shaft
- D. Shearer cutting, support advance and conveyor transfer points
Show Answer
Answer: DDust is created wherever coal and rock are cut, broken or moved. Water sprays, ventilation and respiratory protection are the main controls.
55. What commonly causes high temperatures on deep longwall faces?
- A. Too much fresh air
- B. Heat from the strata and from the power of the machinery
- C. Cold water sprays
- D. Low-output machines
Show Answer
Answer: BRock temperature rises with depth, and the machines add heat on top. Cooling, higher airflow and good ventilation planning become important in deep mines.
56. Why do many powered supports have hydraulically operated face guards?
- A. To cut the coal
- B. To drive the AFC
- C. To hold the coal face and prevent spalling into the walkway
- D. To store hydraulic fluid
Show Answer
Answer: CFace guards swing out to support the face and stop coal from falling onto the walkway, which protects people and keeps the face stable.
57. What does bi-directional cutting mean for a shearer?
- A. The shearer cuts coal while travelling in both directions along the face
- B. It cuts only on the way back
- C. It cuts two seams at once
- D. It moves in one direction only
Show Answer
Answer: ACompared with uni-directional cutting, which has a non-cutting return pass, bi-directional cutting can raise productivity, but it needs good control of the cutting horizon.
58. What is the main aim of longwall automation?
- A. To remove the need for supports
- B. To make the goaf cave faster
- C. To replace ventilation
- D. To keep people away from the face and make cutting and advance more consistent
Show Answer
Answer: DAutomation, such as shearer guidance, face alignment and remote operation, reduces people's exposure and helps the face run more steadily.
59. Where is methane most likely to accumulate on a longwall face?
- A. Only at the shaft bottom
- B. On the surface
- C. At the tailgate end, in roof cavities and near the goaf edge
- D. In the pumping chamber
Show Answer
Answer: CMethane is lighter than air and collects in roof cavities and in areas of poor air movement, such as the tailgate corner. Monitoring points are placed to catch it early.
60. How does shortwall mining differ from longwall?
- A. It is an opencast method
- B. It uses a shorter face, usually worked with a continuous miner and powered supports
- C. It uses no supports
- D. It is used only for steep seams
Show Answer
Answer: BShortwall is a variation with a shorter face length, often using a continuous miner for cutting instead of a shearer.
Answer key
| Q | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 |
|---|---|---|---|---|---|---|---|---|
| Ans | B | D | A | C | B | D | C | A |
| Q | 54 | 55 | 56 | 57 | 58 | 59 | 60 | |
| Ans | D | B | C | A | D | C | B |
Quick revision points from this set
- Stress: front abutment pressure builds up ahead of the face, and side abutment stress acts beside a worked-out panel (chain pillars protect the gate roads).
- Roof: a strong roof that does not cave can fail suddenly, causing heavy weighting and air blasts.
- Gas and ventilation: methane collects at the tailgate end, in cavities and at the goaf edge. Y-type ventilation helps carry goaf gas away.
- LTCC: a rear conveyor takes the top coal drawn through the support's rear opening.
- Health and environment: dust comes from cutting, support advance and transfer points. Heat is a problem in deep faces.
- Operation: keep the face straight, use preventive maintenance and use face guards to stop spalling.
- Technology: bi-directional cutting and automation aim at higher productivity with fewer people at the face.
- Variants: shortwall means a shorter face, usually with a continuous miner.
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 03 Next: Part 05
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