Issue 49

C.Y. Liu et alii, Frattura ed Integrità Strutturale, 49 (2019) 557-567; DOI: 10.3221/IGF-ESIS.49.52

effects of disasters on underground engineering and improve mining efficiency, it is extremely important for scientific research to figure out how to accurately evaluate the brittleness of rocks.

= ⁄ , 2

=

1

( − )

( + ) ⁄ ,

and are the UCS and the tensile strength, respectively.

= 2⁄ , 4

= √ 3

3

5 ′

5 " , 5

′ =

=

5

ε , ε , ε are the peak strain, the peak strain maximum and the minimum value of sample rock specimen, respectively. , , are the standardized coefficients. and are the peak strength and the residual strength, respectively. and are the peak strain and the residual strain, respectively. M and E are the post-peak modulus and the pro-peak elastic modulus, respectively. and are the peak strain and the residual strain, respectively, is the reversible strain of the stress-strain curve. and are the peak strength and the residual strength, respectively.

(

− )/( − ) ,

5 " = + + , CS = ( − )/ / ( − )

= ( − )/ , 7

=

6

/

= ( − )/

,

8

= ( − )/ ,

9

= /

10

11 ′

11 " , 11

′ = 11 " =

=

11

and are the peak strength and the residual strength, respectively.

is the

( − )/

,

post-peak stress drop rate.

lg| | /10

12 ′ = ( − )/( − ) , 12 " = ( − )( − )/( ) = 12 ′ + 12 " , 12

and are the peak strength and the residual strength, respectively,

and

are the peak strain and the residual strain, respectively.

13 ′ + 13

′′ , 13

′ =

=

13

( p

− i

) ( − ⁄

)

and

are the peak strength and the residual strength, respectively.

and

i

′′ =

， 13

are the peak strain and the residual strain, respectively, i and

i are the crack

( p

− r

)⁄ ( − )

initiation stress and the crack initiation strain

=

=

,

14

15

is the inner friction angle determined from Mohr’s envelope.

45° + /2

= 0.5 +

16

0.5

= ( −

,

1)/(8 − 1) ×

E and are the post-peak modulus and the elastic modulus, respectively.

100 ,

= (0.4 − 1)/

(0.4 − 0.15)

where H μ

is the micro-indentation hardness, H m

is the macro-indentation

= ( − )/

17

hardness, and c is the constant

= /

where H a

is hardness and K c

is fracture toughness.

18

= / 2

where H a

and K c

are same as those in B 18

, E is Young’s modulus

19

= /(

+

W qtz

, W carb

and W clay

are the content of quartz, clay and carbonate minerals, respectively.

19

+

),

Table 1 : Formula meaning and explanation.

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