Research Article
An Evaluation Method of Rock Brittleness Based on the Prepeak Crack Initiation and Postpeak Stress Drop Characteristics
Table 3
Brittleness indices for comparative analysis.
| Brittleness | Calculation formula | Parameter specification |
| B1 | B1 = 1 − exp (M/E) [36] | E is the prepeak elasticity modulus; M is the postpeak elasticity modulus | B2 | [35] | τp is the peak compressive strength; τr is the residual compressive strength; kac(AC) is the slope of ac (AC). | B3 | [12] | τp is the peak compressive strength; τr is the residual compressive strength. | B4 | [12] | εp is peak strain; εr is the residual strain | B5 | [37] | εp is peak strain; εB is the residual strain; εM is the prepeak strain when the stress reaches the residual stress. |
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