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.

BrittlenessCalculation formulaParameter specification

B1B1 = 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.