Estimating Strength of Sandstone Using Petrographic Thin-Section Data

Abstract

The determination of rock compressive strength is a major design requirement for underground openings in rock. However, determination of compressive strength by triaxial compression tests requires high quality core samples which are not always available from thin-bedded, fractured strata. This investigation shows that the compressive strength of calcareous sandstones can be estimated from critical petrographic properties observed in thin sections. For the sandstones from the Beehive Coal Mine, the significant petrographic properties are mean and median grain sizes, percent quartz grains, total percent quartz, sphericity, and percent intergrown and percent straight grain contacts. The accuracy of estimating compressive strength can be improved by increasing the number of petrologic properties used as estimators. A polynomial prediction equation utilizing three easily measured rock properties, percent quartz grains, total percent cement, and mean grain size, shows very good correlation between estimated and experimental compressive strengths.