Evaluating the Microstructure and Mechanical Behavior of 3D-Printed Rock Analog and Natural Sandstone via Real-Time X-Ray Computed Tomography

Characterizing the microstructural and mechanical behavior of rock materials under loading is essential for understanding deformation and failure mechanisms. However, the inherent anisotropy and heterogeneity of natural rocks make it challenging to achieve experimental repeatability and isolate the effects of internal structure. To address this, 3D-printed (3DP) rock analogs offer a controllable platform for reproducing rock-like materials with designed porosity and geometry, though their ability to replicate the anisotropic and heterogeneous nature of natural rocks remains uncertain. Therefore, an integrated experimental and analytical framework combining real-time in-situ uniaxial loading tests conducted inside the X-ray computed tomography (CT) scanner, digital volume correlation (DVC), and tensor-based anisotropy quantification was employed to systematically compare the microstructural and mechanical behavior of a 3D-printed (3DP) rock analog with two natural sandstones—white sandstone and Kimachi sandstone in this study. CT-based morphological analysis revealed that the 3DP rock analog possessed a uniformly interconnected pore network with nearly isotropic characteristics, whereas the white sandstone exhibited low porosity but pronounced bedding-related anisotropy, and the Kimachi sandstone displayed moderate heterogeneity and complex pore connectivity. Quantitative anisotropy indices derived from inertia tensors confirmed these distinctions, showing the highest anisotropy in white sandstone and the lowest in the 3DP rock analog. DVC strain field analysis demonstrated that deformation in the 3DP rock analog was spatially uniform until sudden brittle collapse within a basal conical shear zone. In contrast, the white sandstone developed early strain localization along bedding planes, while the Kimachi sandstone exhibited distributed strain evolution governed by microcrack coalescence. The findings highlight a clear structure–anisotropy–mechanical linkage: isotropy promotes uniform deformation; anisotropy induces localized failure and pore connectivity governs the transition between brittle and distributed failure modes. Importantly, while the 3DP rock analog cannot fully replicate the anisotropy and heterogeneity of natural sandstones, its microstructural uniformity makes it ideal for controlled studies of matrix–discontinuity interaction and for calibrating numerical models of rock fracture. Additionally, this work establishes a quantitative multi-scale framework that couples real-time in-situ CT loading, CT-based morphology, tensor-derived anisotropy, and DVC-measured strain evolution, offering new insights into the mechanical fidelity of 3DP rock analog and their implications for experimental rock mechanics.