Some carbonate rock texture effects on mechanical behavior, based on Koohrang tunnel data, Iran

The objective of the study described in this paper is to use correlation analysis and multivariate regression analysis for investigating the effect of physical and petrographic characteristics of carbonate rock on its mechanical properties. The cretaceous carbonate samples from boreholes drilled for preliminary investigations in the Koohrang’s third tunnel path, located in the western part of Shahrekord, Iran, were tested to determine the compressive strength, Young’s modulus, dry and saturated unit weight, porosity, and P-wave and S-wave velocity. Then, samples were subjected to petrographic investigation, including size and percentage of grain, matrix type, dolomitization percent, and carbonate percent. The results showed that compressive strength and Young’s modulus values were related to the dolomite percent, grain size, allochem percent, and carbonate percent. Since no single parameter determined strength and Young’s modulus, polynomial prediction equations were developed for estimating mechanical properties. Dunham’s (1962) classification system appeared to show a correlation with mechanical properties determined for the samples, for example, regarding the organic bounds; some textures such as bindstone and bafflestone indicated the lowest strength and Young’s modulus.