PHYSICAL MECHANISMS OF HARD ROCK FRAGMENTATION UNDER MECHANICAL LOADING: A REVIEW

This Technical Note reviews a number of theoretical and experimental investigations, considers the diversity between them and determines some of the problems that need to be solved. Some of the conclusions of work on microindentation in ceramics can be extended to rocks. The stages of rock fragmentation under indentation are considered and physical mechanisms for the formation of the crushed zone are examined. The influence of the rate of loading, the shape of the indentor and cutting conditions is discussed. Mechanisms of chipping and crack formation are considered. The zone of crushed rock is of great importance in the fragmentation process. The main part of fragmentation energy is apparently consumed just by the formation of the zone and rock crushing within it. The energy of fragmentation increases as the size of the zone increases. The factors influencing the size of the crushed zone, and consequently the energy consumed in drilling, are discussed.