Table 6 Development height of the roof“two zones”in the working face.

From: Overburden failure characteristics and fracture evolution rule under repeated mining with multiple key strata control

Study subjects

Method

Coal seam thickness/m

Height of the WCFZ/m

Fracture-to-mining ratio

Height of the caving zone/m

Caving-to-mining ratio

6#Coal

Physical simulation

3

40.2

13.4

12.4

4.13

Numerical simulation

3

48

16

-

-

Field observation

2.8

33.24 ~ 38

11.9 ~ 13.6

-

-

7# Coal

Physical simulation

9

115

12.8

-

-

Field observation

8.09

99.44 ~ 100.33

12.3 ~ 12.4

43.7

5.4

Repeated mining

Physical simulation

9

139.68

15.5

42.88

4.8

Numerical simulation

9

134

14.9

-

-

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