Estimating Mechanical Properties of Sandstone from Petrographic and Physico-Mechanical Indices Available to Purchase

The mechanical properties of rock, such as unconfined compressive strength, are important to many engineering problems such as slope stability analysis, underground excavation, and drilling mechanics. Many previous studies have proposed relationships that can be used to estimate rock strength properties based on petrographic indices that are easier to measure. In this study, a comprehensive literature review was performed to build a database containing petrographic and mechanical properties for sedimentary rock types. A subset of this database containing only sandstone rock units was used for statistical analyses to develop predictive models. Linear and nonlinear bivariate models were constructed to relate each petrographic and physico-mechanical index variable to each mechanical property. Additionally, multiple regression models were developed using a subset of the petrographic and predictor variables. Contrary to prior studies using smaller data sets, very few correlations were identified, and those that were (for example dry density and mean grain size as predictors of UCS) tended to be for cases where limited data were available for the variables in question. A separate literature review was then performed to find previously-studied relationships that predict the strength properties of sandstones based on petrographic properties. 59 equations for sandstones were found and were tested against the broader sandstones database compiled in this study. It was found that many of these equations were developed for only one type of sandstone and tend to generalize poorly to the broader database.