Full-field mapping of internal strain distribution in red sandstone specimen under compression using digital volumetric speckle photography and X-ray computed tomography

摘要

It is always desirable to know the interior deformation pattern when a rock is subjected to mechanical load.Few experimental techniques exist that can represent fullfi eld three-dimensional(3D)strain distribution inside a rock specimen.And yet it is crucial that this information is available for fully understanding the failure mechanism of rocks or other geomaterials.In this study,by using the newly developed digital volumetric speckle photography(DVSP)technique in conjunction with X-ray computed tomography(CT)and taking advantage of natural 3D speckles formed inside the rock due to material impurities and voids,we can probe the interior of a rock to map its deformation pattern under load and shed light on its failure mechanism.We apply this technique to the analysis of a red sandstone specimen under increasing uniaxial compressive load applied incrementally.The fullfi eld 3D displacement fi elds are obtained in the specimen as a function of the load,from which both the volumetric and the deviatoric strain fi elds are calculated.Strain localization zones which lead to the eventual failure of the rock are identi fi ed.The results indicate that both shear and tension are contributing factors to the failure mechanism.