What is longwall mining?
A
Mining using only hand tools
B
Full extraction mining using a long face
C
Surface excavation of coal
D
Mining with no roof support
Analysis & Theory
Longwall mining is a full extraction underground mining method using a long, continuous face.
In longwall advancing, the face moves:
A
Toward the main roadways
B
Away from the shaft or main entry
Analysis & Theory
In longwall advancing, the face progresses toward the main haulage or shaft.
In longwall retreating, the face moves:
A
Toward the shaft or main entry
C
Horizontally away from surface entries
D
Away from ventilation system
Analysis & Theory
In retreating, development precedes extraction, and the face retreats toward the main entry.
Which is a key requirement for successful longwall mining?
A
Highly variable seam thickness
Analysis & Theory
A strong roof and floor are necessary for safe and efficient longwall mining.
Which method is generally more productive and safer?
Analysis & Theory
Longwall retreating is preferred due to better control, ventilation, and roof conditions.
What equipment is commonly used in longwall mining?
C
Shearer and powered supports
Analysis & Theory
A shearer cuts coal along the face, supported by hydraulic roof supports.
What is a major advantage of longwall retreating over advancing?
A
Easier to ventilate face
Analysis & Theory
Longwall retreating offers better ventilation control and face access.
In which condition is longwall advancing generally used?
B
High spontaneous combustion risk
D
When immediate coal production is needed
Analysis & Theory
Longwall advancing allows early production, useful when urgent output is needed.
One limitation of longwall mining is:
D
No ventilation requirement
Analysis & Theory
Longwall mining involves high initial investment in equipment and setup.
What does 'goaf' mean in longwall mining?
C
Collapsed area behind the face
Analysis & Theory
Goaf is the caved area left behind the face after extraction.
Which of the following is NOT a merit of longwall mining?
C
Safer conditions with mechanization
Analysis & Theory
Longwall has high recovery, typically over 80%.
Which condition is favorable for longwall mining?
C
Regular and uniform seams
D
Seams with large inclines
Analysis & Theory
Longwall mining works best in regular, flat, and uniform seams.
What is the main function of powered supports in longwall mining?
C
Support roof temporarily and advance with the face
Analysis & Theory
Powered supports temporarily hold the roof and move with the advancing face.
A major hazard in longwall mining is:
C
Manual handling injuries
Analysis & Theory
Methane accumulation and spontaneous combustion in goaf can lead to explosions.
Why is face length critical in longwall mining?
A
Affects roof collapse rate
B
Determines loading time
C
Controls production and ventilation
D
Determines color of coal
Analysis & Theory
Face length impacts productivity, ventilation design, and support system efficiency.
Which of the following is a demerit of longwall advancing?
B
Goaf not close to shaft
D
Immediate access to face
Analysis & Theory
The goaf being far from the shaft can complicate safety and ventilation.
What is the ideal seam gradient for longwall mining?
Analysis & Theory
Flat or gently dipping seams allow easier movement of machinery and roof support.
What determines whether advancing or retreating is used?
C
Seam layout, geology, and risk of spontaneous combustion
D
Location of manager’s office
Analysis & Theory
The choice depends on geological and operational factors like seam stability and gas control.
What happens to the roof behind powered supports in longwall mining?
B
It is allowed to collapse in a controlled manner
Analysis & Theory
The roof behind the face collapses forming goaf after supports move forward.
Which is a benefit of mechanization in longwall mining?
C
Consistent production with fewer workers
Analysis & Theory
Mechanization increases efficiency and reduces workforce size needed for extraction.