Effect of loading direction on interaction of two pre-existing open and closed flaws in a rock-like brittle material

Abstract

Investigations of the growth, interaction, and coalescence of cracks are important because they help to provide tools for the more realistic modeling of rock masses containing low persistence discontinuities and better estimations of the strength and stiffness of a rock material. Understanding the coalescence mechanism is useful for justifying the mechanism of continental crustal deformation, evaluating the structural failure of slopes with rock bridges, and analyzing the stability of tunnels when a mode I or mix mode failure mechanism is involved. The evaluation of crack growth can provide valuable information about the mechanism for the formation of new geological structures, and the formation, evolution, and growth of faults. This paper reports the results of diametrical compression tests on rock-like disk-shaped specimens. Each specimen contained two pre-existing open or closed flaws. The growth, interaction, and coalescence of the pre-existing flaws were investigated both physically and numerically. A hybrid bonded particle-finite element system was used in the numerical simulation. The results of the physical and numerical studies were in good agreement. In particular, the induced crack patterns showed close agreement in the physical and numerical tests. Digital microscope image processing was used in the physical tests to study the dislocations along the initial flaws. It was shown that wing crack formation was responsible for the failure of the specimen when flaws were inclined with respect to the loading direction. The crack growth and linkage were shown to be affected by the friction between faces of the flaws. In addition, the slip distributions at the flaws surfaces were illustrated and examined to understand the crack propagation mechanism. The effects of the flaws on the disk failure loads were assessed both numerically and experimentally as well.