Abstract
Among the major sources of variation in correlating uni-axial compression strength from point load index is one related to the point load test type. Axial and diametrical point load tests on cylindrical samples are believed to differ in two main aspects. One is related to the effect of sample orientation and loading direction and the other one concerns the anisotropy issue of the tested rock. In this paper, Uni-axial compression tests were performed on core samples from sedimentary rock units together with two parallel point load tests (axial and diametrical) on rock samples from same core run. Similar tests were performed on identical artificial (concrete) cylinders to observe the effect of load direction with respect to sample geometry on resulted point load index. Data was subjected to linear regression analysis based on least square values. Results showed that diametrical point load index measured only 87 % of the axial index for identical concrete samples. For the tested rock samples, the ratio was only 66 %.Difference from results of the concrete samples is believed to be partially due to the anisotropy of the rock units.