Digital Microscopic Multiphase Heterogeneity Representation and Its Effects on Micromechanics and Cracking Behaviors of Geomaterials

Multiphase heterogeneity significantly affects mechanical and micro-cracking properties of geomaterials. Heterogeneity representations of geomaterials, however, can bring out fatal errors for cracking behavior investigations due to inaccurate characterizations of multiphase matrixes. This work aims to deeply characterize microscopic heterogeneity in rocks represented by digital multiphase matrixes, and to study their effects on cracking properties of geomaterials. X-ray μ-Computed Tomography (μCT) imaging under the same physical field of view is employed to obtain multiphase microstructures of sandstone with different resolutions. Digital colour difference segmentation (DCDS) and the coupling multiple point statistics-marching cube (MPS-MC) algorithms are applied to accurately characterize three-dimensional (3D) multiphase heterogeneity of rocks. Digital simulations coupled with uniaxial compression are conducted to study multiphase heterogeneity effects on micromechanics and cracking behaviors. Results show that with increasing resolution and voxel scale, heterogeneity index increases. Peak stress and crack ratio increase with increasing heterogeneity index, and the relative errors between experimental and numerical stresses are all less than 5% when the voxel is larger than 300³. Micro-pores extremely improve damage of multiphase microstructures, and the transgranular cracks initiate first, and then intergranular cracks initiate due to large heterogeneity of microscopic elements between micro-pores and microscopic interfacial transition zones (ITZs) and similar strength heterogeneity of microscopic elements in micro-grains. The proposed digital-analysis framework is effective to evaluate multiphase heterogeneity effects on mechanical and cracking responses in various engineering projects.