Table 4 Mechanical param of rock mass.

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

Lithology

Density/kg/m3

Tensile strength/MPa

Bulk modulus/GPa

Shear modulus/GPa

Angle of internal friction/°

Cohesion/MPa

Loose strata

1300

0.13

0.41

0.15

15

0.15

Siltstone

2160

1.55

7.34

6

32.1

1.95

Coarse sandstone

2700

1.39

10.70

9.26

40

2.09

Sandy mudstone

2520

1.13

5.52

1.7

38

1.72

Fine-grained sandstone

2790

2.27

10.14

6.27

37

1.49

Medium sandstone

2640

1.45

9.7

8.3

39

1.83

6#coal seam

1370

0.81

5.4

2.4

27

0.8

7#coal seam

1370

0.81

5.6

2.4

27

0.8

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