Relationship of brittleness and fragmentation in brittle compression

The aim of this research is to investigate whether a relationship exists or not between various brittleness concepts and fragmentation of rock under brittle compression. The term 'brittleness' at present has no clear definition. Fragmentation of rock under compression depends on it self-sustaining failure and the energy available at the peak strength to shatter the rock. It appears from review of the literature that no research has attempted to link rock brittleness and its corresponding fragmentation in compression. Rock failure under conventional compression tests and the subsequent fragments size distribution is a little-understood phenomenon. The research carried out involved determination of post-peak modulus for various rocks using a closed loop servo-controlled testing machine and fragmentation of the rock in brittle compression in accordance to ISRM (2007) suggested methods. Various brittleness concepts were evaluated from static mechanical properties, energy balance, normalised pre-failure curves and extension strain criterion. They were compared with fragments size obtained from compression. Brittleness concepts form static mechanical properties show that the higher its value the finer the fragmentation. Both concepts from normalised pre-failure curves and extension strain criterion appear to treat fragmentation of Class I and Class II rocks as a separate entity. They show better correlation with fragmentation for the segregated samples, Class I and Class II than other concepts. The concepts correlated with the post-peak modulus of the rocks and as such could be useful to quantify the brittleness of the rock under compression.