Table 3 Three typical GSI classified rock masses (used for three different types of overburden) and their properties, provided by Hoek52.

From: A new indicator for estimating the degree of mining-induced land subsidence: the overburden’s average GSI value

Rock parameters

Very good quality overburden

Average quality overburden

Very poor quality overburden

Geological strength index

75

50

30

Hoek–brown constant

25

12

8

Friction angle

46°

33°

24°

Cohesion

13 MPa

3.5 MPa

0.55 MPa

Tensile strength

0.9 MPa

0.15 MPa

0.01 MPa

Young's modulus

42,000 MPa

9000 MPa

1400 MPa

Poisson's ratio

0.2

0.25

0.3

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