Herewe investigate the classification of weathering grade for granitic rocks fromthe Malayer granitoid,western Iran, using physico-mechanical parameters. The physical and mechanical properties of rock samples were measured across five weathering grades ranging from fresh rock to completely weathered. Statistical analyses, including simple regression and multiple linear regression, were applied to identify those physico-mechanical parameters that are most influenced by the progression of weathering. The parameters with significant correlations with weathering grade include strength retention index, p-wave velocity, porosity, Brazilian tensile strength, and point load index. On the basis of the statistical results, newclassifications are developed. These classifications can be used to predict the engineering properties of the Malayer granitic rocks (Hamedan, NW Iran) and should have more general application to the quantitative classification of granitic rocks in Iran.
