Correlation between uniaxial compressive strength and point load strength index of granite sample

Abstract

Uniaxial compressive strength (UCS) of rocks is an important parameter in geotechnical structure designs. Being difficult to obtain proper sample and the UCS test itself is expensive, indirect methods of estimating UCS were developed such as point load test. In this study, an attempt has been made to correlate the point load strength index (Is(50)) with the UCS for local granite. The Is(50) is widely used to determine the rock strength by estimating the UCS using conversion factor, ?. The Is(50) value is known to correlate well with UCS. Various studies have come out with correlation between UCS and Is(50) . It is found that the index-to-strength conversion factors are rock dependent. This study presents the correlation between UCS and Is(50) of granite rock samples originating from a site located at Seremban, Negeri Sembilan. Seven granite rock samples underwent uniaxial compressive test. A correlation between these two parameters was generated from the graph giving an equation of UCS = 4.8231 Is(50) + 25.201. From the results obtained and the observation made in this study, it is suggested that future study to employ a well-designed laboratory works considering factors such as larger sample size, diversity of rock type and better rock quality to ensure a more reliable correlation can be produced.