Correlation between point load index and uniaxial compression strength for claystone from Caycuma formation Kocaeli, Turkey

Evaluation of rock engineering properties is a significant phenomenon for mining, civil and geotechnical engineering disciplines. Uniaxial compressive strength is one of the most important engineering parameters and it is used to characterize rocks from the strength point of view. The procedure to determine the uniaxial compression strength is standardized by International Society of Rock Mechanics Commission on Testing Methods (ISRM) and American Society for Testing and Materials (ASTM). The indirect method proposed by the societies are generally preferred to evaluate the uniaxial compressive strength utilizing the point load test because of simplicity and inexpensiveness of application. Numerous correlations are offered in the literature those are integrating uniaxial compression strength to the point load strength index. These equations’ variability range is very large depending on the rock type and geological conditions. Because of these fundamental changes of equations it becomes important to select the proper index for the determination of rock strength. This paper involves point load tests of clay stones which are a member of Caycuma formation of Kocaeli province for evaluating the uniaxial compression strength. 208 point load tests and 30 uniaxial compression tests are used to identify Caycuma formations’ characteristics throughout fifty meters depth. As a consequence, an appropriate particular index value for calculating Caycuma clay stones’ uniaxial compression strength is achieved with the correlations subjected to the point load tests.