Rock fragmentation and optimization of drilling tools

In this chapter possibilities of the improvement of drilling tool efficiency on the basis of the analysis of mechanisms of rock destruction and some methods of the information theory are considered. Physical mechanisms of destruction of hard and plastic rocks under different conditions of mechanical loading are reviewed. Some physical effects which allow to improve the efficiency of rock drilling tool are listed and ways of tool improvement are discussed. It is shown experimentally that the efficiency of drilling by a multicutter drilling tool may be improved by using the interaction between crack systems from neighboring cuts. It was suggested to apply methods of the theory of information to model complex processes of rock destruction and rock/tool interaction. Several examples of using of the information theory methods are given (stress distribution in disordered rocks, indexing effect, tool wear, optimization of complex tool construction). The general principle of tool improvement is formulated on the basis of the informational models.