Application of Index Test Methods for Intact Rock Strength Assessment
AdvisorKallu, Raj R
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Uniaxial compression strength of intact rock is important for engineering geology and geotechnics, because it is an important design parameter for mines, tunnels, slopes, and rock foundations. It is also used as input parameter in most the rock mass classification systems. The difficulties associated with performing direct compression strength tests on rock leads to indirect test methods for the rock strength assessment. Indirect test methods are widely used because they are simple, more economical, less time consuming, and easily adaptable to the field. The main aim of this study is to define correlations between direct and indirect test methods for core samples from a gold mine in NV. The indirect test methods are divided in two groups of (1) destructive indirect test methods and (2) non-destructive indirect test methods. In the destructive methods, point load index (PLI) tests, splitting tensile strength (Brazilian) tests, and block punch index (BPI) tests are conducted. In the non-destructive methods, Schmidt hammer and ultrasonic pulse velocity tests are performed. The results demonstrate that the block punch index test is not applicable to these rock types. Eleven correlations between the direct and indirect compression strength tests are developed using linear and nonlinear regression analysis methods. To evaluate the performance of each regression equation, coefficient of correlation (R2), variance accounted for (VAF), root mean square error (RMSE) and mean absolute error (MAE) were calculated. The results show that the splitting tensile strength has the best correlation relation with the uniaxial compression strength. Furthermore, the Poisson's ratio has no correlation relation with any of the direct and indirect test results.