Over riding of pillars, premature collapse cover due to presence of
A. Strong coal
B. Shale roof
C. Watering strata
D. Strong thick massive sand stone
Answer: Option D
This Question Belongs to Mining Engineering >> Coal Mining
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The required water for 1 ton of sand in hydraulic sand stowing is . . . . . . . .
A. 800 l
B. 600 l
C. 1100 l
D. 1200 l
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