A. coal left in underground for unfavourable geological conditions
B. coal left to protect surface features
C. coal loss due to spon heating
D. coal left as ribs within the pillars
Answer: Option D
This Question Belongs to Mining Engineering >> Introduction To Mining Engineering
A. Normal distribution
B. Skewed distribution
C. Lognormal distribution
D. Poisson distribution
A. 3 level heading district
B. 4 level heading district
C. 5 level heading district
D. 6 level heading district
It is very difficult to control shaley roof if coal is not left with the shale why?
A. It is weak in nature
B. It has weathering effect
C. It has great affinity to absorb moisture and get departed from immediate roof
D. It reacts with coaly surface
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