Which of the following is not a common way for coal caving? ( )
A: Top caving coal in group sequence
B: Top caving coal in single cycle sequence
C: Top caving coal in multiple cycles in sequence
D: Top caving coal in intervals of single cycle
A: Top caving coal in group sequence
B: Top caving coal in single cycle sequence
C: Top caving coal in multiple cycles in sequence
D: Top caving coal in intervals of single cycle
举一反三
- During top coal caving mining, the essential cause of top coal crushing is ( ). A: softening of water in roof strata B: the stress it beared is large than its own strength C: the gas in the top coal expands, leading to breakage D: cracks produced by raw coal during its formation
- What are the main disadvantages of fully mechanized caving technology? ( ) A: More coal loss B: Fire prone C: Big coal dust D: Gas is easy to accumulate
- The most easily oxidized coal is (). A: lignite coal B: bituminous coal C: lean coal D: anthracite coal
- While it has set targets to increase its consumption of ( ), China remains the world’s top producer and consumer of coal
- The dry ash free volatile content of a coal is 7%, which is most likely to belong to (). A: Bituminous coal B: Anthracite C: Lignite D: Lean coal