Evaluation of unconfined compressive strength of carbonate sedimentary rocks in Saudi Arabia using indirect tests

Unconfined compressive strength (UCS) of rocks, determined by loading the rock specimens along their longitudinal axis without lateral restraint, is one of the important engineering properties required for assessing the mechanical behavior of the rocks. However, determining UCS using direct method requires stringent sample preparation and testing that need higher costs and longer time. Therefore, the evaluation of UCS of rocks using the correlations developed empirically between UCS and some relevant parameters obtained through indirect tests on rocks would be an alternative approach. In the present work, 40 samples of carbonate sedimentary rocks, belonging to Cenozoic deposits of the Great Ghawar Uplift geological province, near Ain Dar, Saudi Arabia, were collected. All samples of rocks were tested to determine their mass density, ρ, point load strength index, I_s(50), ultrasonic pulse velocity, V_p, and UCS. The test results were analyzed and the correlations of UCS with ρ, I_s(50), and V_p were obtained for indirect estimation of UCS of the rocks considered under this study. The relationship between UCS and V_p showed highest degree of fit among three relationships followed by the relationships between UCS and ρ and UCS and I_s(50).