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
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
The stage natural caving method is the most economical of all mining methods. If the conditions are suitable, it can also achieve high production capacity.
The stage natural caving method is the most economical of all mining methods. If the conditions are suitable, it can also achieve high production capacity.
The stage natural caving method is the most economical of all mining methods. If the conditions are suitable, it can also achieve high production capacity. A: 正确 B: 错误
The stage natural caving method is the most economical of all mining methods. If the conditions are suitable, it can also achieve high production capacity. A: 正确 B: 错误
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
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
This passage mainly talks about ____.() A: the writer’s friends at the Activity Centre B: the writer’s experience at the Activity Centre C: outdoor sports at the Activity Centre D: how to go rock-climbing and caving
This passage mainly talks about ____.() A: the writer’s friends at the Activity Centre B: the writer’s experience at the Activity Centre C: outdoor sports at the Activity Centre D: how to go rock-climbing and caving
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
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