Estimation of compressive strength and tensile strength of carbonate rocks using point load index test and their correlation with aggregate impact value (case study: Kermanshah-Ilam Road carbonate rocks)

Determination of geotechnical parameters required for design of rock mass structures are one of the major issues in the engineering geology, civil and mining. Uniaxial compressive strength and tensile strength are among of these parameters which are widely used in the design of structures in rock mass. Among them, the point load index test not only has less cost and difficulty than uniaxial compressive strength and tensile strength tests; but also can be carried out at the site of the project and on samples with irregular geometry; therefore, it can be used as a criterion for the initial engineering judgment regarding tensile and compressive strength of rocks. In the research, the relationship between these parameters is analyzed with statistical analysis and the best experimental relations are presented. Moreover, due to the vast spatial occurrences of carbonate rocks in the country and their application in various development projects, the relationship between uniaxial compressive strengths, tensile strength and point load strength with aggregate impact value is also studied, which is one of the indicators for assessing the quality of materials stone. In the bivariate equations, the highest coefficient of determination is 0.897, that related to the relationship between the uniaxial compressive strength and the point load index in dry condition and the lowest coefficient of determination is 0.653, that relates to the relationship between the Brazilian tensile strength and the aggregate impact value in dry condition, also the use of multivariate regression leads to a much better estimate of uniaxial compressive strength.