Table 1 The rock mechanics testing results of immediate roof for No. 8 seam.

From: Prediction of elevation of substantial fluctuation in coal seam floor based on surface spline function and its derivative

Drilling number

Lithology of

Immediate roof

Compressive strength (MPa)

Softening coefficient

(MPa)

Tensile strength

(MPa)

Shear strength

(MPa)

Natural state

Saturation state

ST302

Coarse sandstone

6.2 ~ 18.4

10.3 ~ 15.9

0.95

0.53 ~ 1.43

1.34 ~ 1.78

Siltstone

19.4 ~ 28.4

19.0 ~ 30.3

0.97

1.13 ~ 1.71

4.85 ~ 8.41

ST306

Fine-sandstone

17.5 ~ 30.4

11.0 ~ 28.9

0.87

0.65 ~ 0.81

1.73 ~ 2.27

Sandy mudstone

12.0 ~ 22.2

15.3 ~ 20.0

0.99

1.09 ~ 1.21

3.06 ~ 4.03

ST703

Mudstone

27.6 ~ 33.7

11.2 ~ 23.4

0.53

1.14 ~ 1.16

3.06 ~ 5.21

Coarse sandstone

10.0 ~ 49.6

11.2 ~ 15.8

0.36 ~ 0.71

0.82 ~ 3.32

1.73 ~ 3.23

ST708

Fine-sandstone

19.5 ~ 35.9

16.1 ~ 22.7

0.67

1.51 ~ 1.84

4.13 ~ 4.33

Coarse sandstone

13.3 ~ 25.5

10.7 ~ 23.8

0.88

0.82 ~ 0.93

2.56 ~ 4.03

Sandy mudstone

23.2 ~ 37.3

19.7 ~ 32.2

0.88

0.58 ~ 1.38

2.41 ~ 2.93

Mudstone

18.2 ~ 25.1

9.1 ~ 24.1

0.74

0.42 ~ 0.72

3.09 ~ 4.08

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