Characterisation of tensile damage in rock samples induced by different stress paths

Cracks, induced by different stress states, are studied systematically on thin slices of crinoidal limestone samples. Samples damaged by tension are compared to samples in which first damage is induced by compressive stresses, followed by tensile stresses. To quantify the effect of the compressive stresses, samples only damaged by compression are also studied. The tensile stresses cause the occurrence of an intergranular crack. When the sample is first damaged by compressive stresses, former induced damage influences the growth of this crack. It results in an intergranular crack with a zigzag profile. The average orientation of the intergranular crack is, however, the same as in the samples damaged by tension only.