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Abstract Rock-like specimens were made in the laboratory to have two pre-existing transfixion cracks of designated size and inclination. The failure characteristics of the specimens were studied using conventional triaxial compression tests. The macroscopic fracture trace of the samples shows the characteristics of coplanar cracks，anti-wing cracks and wing cracks. The two pre-existing cracks may be linked by stretching coalescence or shear coalescence，or one crack may propagate to link with the other via an anti-wing crack，or the two pre-existing cracks may not be linked. Under triaxial loading conditions，the anti-wing crack is the major propagation crack，which affects the final failure mode of the samples. The arrangement of the two pre-existing cracks and the confining pressure are the two main factors that dictate the final failure mechanism of the specimens. The axial stress-strain curves of the samples show multi-peak characteristics under triaxial loading conditions and the deformation characteristics change from brittle behaviour under low confining pressure to more ductile under high confining pressure conditions. Under high confining pressure，the dilation is insignificant or almost nonexistent. The axial stress-strain curves are closely related to the processes of fracture initiation，fracture propagation and fracture coalescence.
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2015, Vol. 34 
