Table 7 Thickness of waterproof safety coal rock pillar protective layer.

From: Study of the mining and aquifer interactions in complex geological conditions and its management

Cover rock lithology

Cohesive soil thickness at the bottom of loose layer is greater than cumulative mining thickness

Cohesive soil thickness at the bottom of loose layer is less than cumulative mining thickness

Loose layer full thickness

Noncohesive soil layer at the bottom of loose layer

Stiffness

4A

5A

6A

7A

Medium-hard

3A

4A

5A

6A

Soft

2A

3A

4A

5A

Extremely soft

2A

2A

3A

4A

  1. Note: 1. \(A = \frac{\sum M }{n}:\;\sum M\)—Cumulative mining thickness; n—layer number; 2. Suitable for gently inclined (0° ~ 35°), inclined (36° ~ 54°) coal seams.
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