Evaluating the effect of grain size on mechanical parameters of rocks from different areas of Khyber Pakhtunkhwa, Pakistan

Abstract

Granite is one of the important rocks commonly used as building, dimension and decorative stone. Before using these rocks for any purpose, the mineralogical, petrographic, textural and mechanical properties are important to be evaluated. In this study the effect of textural features on the strength properties especially compressive strength, tensile strength and Hoek- brown parameters, were evaluated of eight different granite deposits from various areas of Khyber Pakhtunkhwa. Hoek – Brown constants (mi and a) were determined for granite of Malakand and Shewa Shahbaz Garhi, using linear regression fitting technique on the full scale laboratory data on established empirical models of Hoek- Brown, Mostyn & Douglas, Generalized Hoek & Brown model, and roclab software. Two linear empirical equations were developed for quantitatively estimation of compressive and tensile strength based on grain size. The result shows that the value of compressive and tensile strength increases when grain size is decreases from very coarse to fine grained and there is little effect of grainn size and texture on the Hoek-Brown failure criterion parameters. It is concluded that the generalized variant of Hoek & Brown failure criterion is more precisely described the behavior of the rock at different stress level.