Indirect Estimation of Rock Tensile Strength Based On Simple and Multiple Regression Analyses

Tensile strength (TS) is one of the most important parameters for investigation of rock behavior in civil and mining engineering applications. The direct method to determine TS is timeconsuming and expensive in the laboratory. Therefore, indirect estimation of TS values using other rock index tests is of interest. In this study, an extensive laboratory tests including density, p-wave velocity, Schmidt hammer, point load strengthand Brazilian tensile strength (BTS) were conducted on 87 samples of granite which were taken from the face of the Pahang–Selangor fresh water tunnelin Malaysia.Based on the laboratory results, some new equations with acceptable reliability were developed to predict BTS using simple regression analysis. Additionally, results of simple regression analysis show that there is a need to propose BTS predictive models by multiple-inputs. Therefore, considering the same laboratory results, multiple regression (MR) model was also performed. In order to evaluate performance prediction of the developed models, several performance indices i.e. coefficient of determination (R2), variance account for (VAF) and root mean squared error (RMSE) were examined. The results indicated that the developed MR model can predict BTS with higher performance capacity compared to simple regression technique.

Tensile Strength, Rock Properties, Simple Regression, Multiple Regression