No abstract

No abstract

The importance of the stress path on pre-peak (micro-) damage in rock material is addressed. Cracks, induced by macro-compressive stresses and macro-tensile stress fields are studied systematically on thin slices of crinoidal limestone samples. The effect of the sequence of macro-compressive and tensile stress fields, on the presence of the cracks is quantified. Firstly, samples damaged by compressive stresses only or tensile stresses only are studied. Hereafter, as a first case, a sample damaged firstly by compressive stresses and secondly by tensile stresses is studied. As a second case, samples damaged firstly by a tensile stress field, followed by compressive stresses are studied and compared to the first case. In the discussion, also the recorded cumulative acoustic emission energy and the clustering of acoustic emission events are used. The differences of both cases are highlighted: in the second case, more damage is observed than in the first case.

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.

No abstract