Development of rock bitwear models for selected rocks in Nigeria using dominant rock properties

This work deals with the development of wear rate models for some selected rocks in Nigeria. Rock samples obtained were tested for chemical composition, point load strength index, uniaxial compressive strength, and porosity in the laboratory. These properties were correlated with wear rate. The results of statistical correlation matrix revealed that silica content, point load strength index, uniaxial compressive strength, porosity, Equivalent Quartz Content (EQC), rebounds hardness value and circularity factor are dominant rock properties affecting bit wear having high coefficient of correlation. These rock properties were used for development of regression model to predict wear rate for each of the selected rocks. The regression equation for predicting bit wear rate of porphyritic hornblende-granite is WG = 0.135 – 0.001 Is50 – 0.002EQC – 0.007n, the regression model has multiple correlation coefficient of R₂ = 0.992 (99.2%), which means that 99.2% of the variation in wear rate can be attributed to variation in point load strength Index (Is50), Equivalent Quartz Content (EQC) and porosity (n) of porphyritic hornblende-granite. The results of comparison between field measured wear rate and simulated wear rate followed the same trend and the coefficient of correlation between wear rate (dependent variable) and regression standard predicted value is R₂ = 0.99, which suggest that the models are valid.