(1) The depth of the borehole is determined based on each progress, and generally there are three types of progress (A), which are suitable for the length of the top beam of the individual support.

A. 0.8m, 1.0m, 1.2m

B. 1.0m, 1.2m, 1.4m

C. 1.2m, 1.4m, 1.6m

2. According to the current mining technology conditions in China, the length of the blasting mining face in gently inclined coal seams is generally (C) m.

A. 70~~110

B. 90~130

C. 80-120

3. When the advancing degree of the blasting mining face is 1m each time, the top beam of (B) can be selected.

A. 0.8m

B. 1.0m

C. 1.2m