A dilatancy model of tensile macrocracks in compressed rock

A model is developed for tensile fracture under compression for a brittle m aterial with microcracks. The final stage of failure with the formation of macroscopic-splitting cracks is considered. Pre-existing microcracks act as a converter of compression into tension in one direction. This results in the nucleation of other tensile microcracks. Rupture of spacings between th e microcracks generates a mode I macrocrack parallel to the direction of ma ximum compression. Crack propagation is due to sliding along planes that ar e inclined to the compression microcrack surfaces and is stimulated by the forces distributed along the interacting macrocrack surfaces. Equilibrium, stability and growth of cracks are studied on the basis of the theory of fr acture mechanics under the assumption of the plane strain state. The behavi our of both short and long macrocracks are analysed. Parameters of the mode l are evaluated with the help of data from fracture experiments on some roc ks.