Evaluation of rock brittleness indices to estimate Cerchar Abrasivity Index for disc cutter weariness

Rock brittleness indices introduced in the literature as a function of different combination of uniaxial compressive strength (UCS), Brazilian tensile strength (BTS) and density (D) are evaluated to estimate the CAI of rocks herein. For this aim, 80 tunnel cases all around the world were examined to obtain the raw data; then the data set was established. The dataset includes UCS, BTS, Density (D), and brittleness index (BI0) and the CAI of rocks. Further, the brittleness indices; BI1 (the ratio of UCS to BTS), BI2 (the ratio of UCS minus BTS to UCS plus BTS) and BI3 (square root of the UCS multiply BTS divided by two) and also BI4 and BI5 (as a function of UCS, BTS and D) were computed and recorded into the dataset. Then, several alternative linear and non-linear regressions are conducted to obtain the relations between CAI and relevant rock brittleness indices. It is found that the brittleness indices BI1, BI2 and BI4 are not good enough to estimate the CAI; however, BI0, BI3 and BI5 showed that the CAI can be estimated as a function of rock brittleness with correlation coefficient (r) of 0.650, 0.775 and 0.685 respectively.