The axial cleavage fracture 1 Axial cleavage fracturing, a significant process in mining and geology

Abstract

The attention is called to the systematic occurrence of fracturing in brittle rock parallel to the major load axis at triaxial differential compressive loading. The axial fracture plane shows the features of the tensile brittle ( cleavage) fracture; this circumstance has led to the nomenclature “axial cleavage fracture”. The historical development about the knowledge of axial fracturing is described. In view of experimental data the well-known physical theory of Griffith has been adapted to explain axial fracturing. It is shown that axial fracturing occurs in the direction of the principal plane bearing the minor principal stress, thus forming a pilot-plane. A model for the fracture-tip has been proposed and discussed. This model will lead to a simple formula for an equilibrium in case of cataclastic occurrence of axial cleavage fracturing in brittle rock. The process of failure has been analyzed and the different structural changes are pointed out. This has been represented in a Mohr's diagram with envelopes. Different material states are defined on the mode of permanent deformation, fracturing included.