If you have been following this series, you already know the basic layout of a longwall panel and how the roof behaves around it. Part 3 moves to the details that exam setters love: how the shearer and plough actually cut, how supports are designed and controlled, what the floor and roof layers do, and how gas, dust and ignition risks are managed.
Previously we covered Part 1 (basics) and Part 2 (advancing and retreating, caving, periodic weighting). This set has 15 new questions (Q31 to Q45). Try each one first, then tap Show Answer and read the explanation.
Longwall Mining MCQs: Part 03 (Q31 to Q45)
31. Which type of powered support has a caving shield that keeps rock from the goaf out of the working area?
- A. Roof bolt
- B. Shield support
- C. Steel arch
- D. Wooden chock
Show Answer
Answer: BShield-type supports have a canopy over the face and a caving shield at the rear, which holds back debris falling from the goaf. Chock-shield supports combine features of both designs.
32. In longwall terminology, what does the 'face length' mean?
- A. The length of the coal face between the maingate and the tailgate
- B. The distance the face retreats during the life of a panel
- C. The length of the shearer
- D. The height of the seam
Show Answer
Answer: AFace length is the width of the panel, measured along the face from the maingate to the tailgate. The distance the face retreats is the panel length.
33. What is the function of the ranging arm of a shearer?
- A. To push the AFC forward
- B. To spray water on the drums
- C. To lock the shearer onto the conveyor
- D. To raise or lower the cutting drum so it can cut from floor to roof
Show Answer
Answer: DEach ranging arm carries a cutting drum and can be raised or lowered by hydraulic rams. This lets the shearer follow the seam and cut the full section.
34. What is the 'web' of a shearer?
- A. The conveyor chain
- B. The wire mesh hung under the roof
- C. The depth of the slice of coal cut by the drum in one pass
- D. The electric cable
Show Answer
Answer: CThe web is how far the drum cuts into the face on each pass. After the cut, the AFC and the supports advance by roughly that amount.
35. How does a longwall plough remove coal?
- A. By shaving a thin slice off the face as it is pulled along by a chain
- B. By rotating drums fitted with picks
- C. By blasting with explosives
- D. By jets of high-pressure water
Show Answer
Answer: AA plough is pulled along the face by a chain and planes off a thin layer each time it passes. That is why it suits relatively thin seams.
36. Why is a finished longwall panel usually sealed off with stoppings?
- A. To save timber
- B. To increase coal production
- C. To collect water
- D. To stop air leaking through the goaf, which prevents spontaneous heating and contains gases
Show Answer
Answer: DAir passing through broken coal in the goaf can cause heating. Sealing the panel limits air entry and keeps goaf gases contained.
37. What is the main purpose of methane drainage in a gassy longwall panel?
- A. To increase the moisture in the coal
- B. To remove methane from the seam and goaf before it enters the face air
- C. To cool the shearer
- D. To lubricate the supports
Show Answer
Answer: BDrainage boreholes capture methane before it can flow into the working area, which reduces the load on the ventilation system and the explosion risk.
38. Prolonged exposure to respirable coal dust at the face can cause:
- A. Malaria
- B. Decompression sickness
- C. Coal workers' pneumoconiosis
- D. Scurvy
Show Answer
Answer: CCoal workers' pneumoconiosis, commonly called black lung, is an occupational lung disease. Water sprays, ventilation and respiratory protection are the main controls.
39. What is meant by the 'immediate roof' of a longwall face?
- A. The strata directly above the seam that caves soon after the supports advance
- B. The strong main roof high above the seam
- C. The floor under the seam
- D. The roof of the gate road only
Show Answer
Answer: AThe immediate roof is the weaker layer lying right on top of the seam. It is held up by the supports and falls into the goaf behind them. The stronger main roof above it breaks later and causes periodic weighting.
40. Why must the height range of a powered support suit the seam thickness?
- A. So the shearer can climb over it
- B. So it can be set firmly against both roof and floor even as the seam height varies
- C. To make it look neat
- D. To reduce water consumption
Show Answer
Answer: BEvery support has a minimum and a maximum working height. If the seam is thicker or thinner than that range, the support cannot hold the roof properly.
41. What can happen if the load on a support's base exceeds the bearing capacity of the floor?
- A. The roof becomes stronger
- B. The AFC speeds up
- C. Methane increases automatically
- D. Floor punching, where the base sinks into the floor
Show Answer
Answer: DWeak floor strata can give way under the base of the support, which lowers the support's effective height and makes advancing difficult.
42. What is the installation roadway (set-up room) of a longwall panel?
- A. The roadway across the end of the panel where the face equipment is installed before extraction starts
- B. A roadway for storing explosives
- C. The surface building for the winder
- D. Another name for the sump
Show Answer
Answer: ATo start a panel, the shearer, AFC and supports are installed in a roadway driven across the panel. At the end of the panel, the equipment is recovered through a similar recovery roadway.
43. Why are electro-hydraulic control systems used on powered supports?
- A. To cut the coal
- B. To pump water out of the mine
- C. To operate supports remotely or in sequence, keeping people out of dangerous positions
- D. To measure the gas concentration
Show Answer
Answer: CThese systems let supports be moved from a safe position or in an automatic sequence, which makes the face safer and faster.
44. Which of the following can cause frictional ignition on a shearer?
- A. Wet coal
- B. Worn or blunt picks striking hard strata such as sandstone or pyrite
- C. Fresh air
- D. Clean picks cutting soft coal
Show Answer
Answer: BSparks from picks hitting hard rock can ignite methane. Sharp picks, water sprays and good ventilation help reduce the risk.
45. Longwall mining is generally most economical when:
- A. The seam is steep and badly faulted
- B. Reserves are small and scattered
- C. Only a very small output is needed
- D. Reserves are large, the seam is fairly regular, and the panels are long enough to justify the capital cost
Show Answer
Answer: DLongwall equipment is expensive, so it pays off when the geology is regular and enough coal is available to be extracted from long, continuous panels.
Answer key
| Q | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 |
|---|---|---|---|---|---|---|---|---|
| Ans | B | A | D | C | A | D | B | C |
| Q | 39 | 40 | 41 | 42 | 43 | 44 | 45 | |
| Ans | A | B | D | A | C | B | D |
Quick revision points from this set
- Terms: face length is the width of the panel, and web is the depth of coal cut by the drum in one pass.
- Cutting machines: the shearer cuts with rotating drums on ranging arms, and the plough shaves thin slices off the face.
- Supports: shield supports have a caving shield, their height range must suit the seam, and a weak floor can lead to base punching.
- Roof: the immediate roof caves first, and the main roof above it causes periodic weighting.
- Safety: methane drainage, sealing of finished panels, dust control, and avoiding frictional ignition from worn picks.
- Layout: equipment is installed in an installation roadway and recovered through a recovery roadway at the end of the panel.
- Economics: longwall pays off in regular seams with large reserves.
Note: these questions are for practice and revision. Terms and figures 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 02 Next: Part 04
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