Investigation of strain fields and anisotropy in triaxial tests on Callovo-Oxfordian claystone by X-ray micro-tomography and digital volume correlation

The objective of the present study is to investigate deformation behavior of anisotropic claystone in relation with material heterogeneity. For this purpose, a set of five triaxial compression tests are performed on samples of Callovo-Oxfordian (COx) claystone under in-situ X-ray micro-tomography monitoring. Complete 3D images of the samples full loading history were recorded and analyzed by digital volume correlation method. Full non-uniform strain fields were determined and averaged global strains were calculated. As novelty, we have particularly investigated the effects of bedding planes, initial cracks and confining stress on strain fields. The results indicate that the structural anisotropy of COx claystone has a strong influence on the local strain distribution and cracking process. The confining pressure has also an important impact on the strain fields and failure modes of samples in the triaxial tests. The cracking process of samples is strongly correlated with radial strain distribution.