Use of the block punch and point load tests to predict the compressive strength of gneissic rocks; with particular reference to the size effect

Various correlations have been established with regard to rock strength indices for different types of rocks around the world. In Sri Lanka, having several types of sedimentary and metamorphic rocks, least attempt has been made in relation to the particular subject area. In order to fulfil the need to a certain extent, this research was carried out to study correlations between rock strength indices specifically in Sri Lankan gneissic rocks. The study reveals information with regard to an emerging, yet powerful rock strength index known as Block Punch Index, which could be used with same significance as that of Point Load Index, while predicting Uniaxial Compressive Strength. The study further compares the strength indices and their variations in relation to size effect. It finally presents conclusions drawn relating to strength indices of Sri Lankan gneissic rocks with several recommendations