Predicting the strength and brittleness of rocks from a crushability index

Uniaxial compressive strength (UCS), Brazilian tensile strength (BTS), and brittleness are widely used in rock engineering applications. However, preparing the test samples for the standard tests may not always be possible for weak or soft rocks. On the other hand, only rock fragments may be available to estimate the rock strength in some cases such as drilling. Therefore, developing some models for estimating the rock strength and brittleness from rock fragments will be useful. In this study, a crushability index (CI) was described from the crushing test, and the possibility of predicting UCS, BTS, and brittleness from this index was investigated. Strong and significant linear correlations were found between the CI and UCS, BTS, and one of the brittleness concepts. It was concluded that the UCS, BTS, and some brittleness concepts of rock could be estimated from the CI. The suggested method is especially useful for the drilling industry and for the cases where there are not enough samples for the standard tests. However, the study is a preliminary study on limited rock types and further study is required by including the number of different rock types.