Mechanical characterization of uniaxial compression associated with lamination angles in shale

This paper investigates the mechanical properties and damage laws of marine shale from the Silurian Longmaxi Formation by conducting uniaxial compression experiments with varying lamination angles with respect to the loading direction. Data are analyzed via computed tomography scanning and fractal theory to reveal a series of mechanical properties, considering stress-strain curve, compressive strength, Young’s modulus, and Poisson’s ratio. The results indicate three damage modes in shale samples: shear, tension shear, and tension. The shales are anisotropic as the mechanical properties vary with the lamination orientation and the loading direction. The compressive strength decreases nonlinearly with increasing lamination angle, whereas the Young’s modulus and Poisson’s ratio correlate almost linearly with the lamination angle. To overcome the defect of visual images when quantitatively evaluating cracks and rock damage to investigate the mechanical properties of shale, we propose block fractal dimension and crack fractal dimensions calculated using post-experimental photographs and computed tomography images. Fractal dimensions are useful tools for identifying variations in uniaxial compressive strength and correlate positively with the sample damage, particularly their damage class. This study highlights the value of applying fractal theory for the quantitative characterization of shale mechanical properties, and reveals that the lamination orientation to the loading direction is a parameter that significantly controls the mechanical properties of shale.Document Type: Original articleCited as: Gao, M., Yang, M., Lu, Y., Levin, V. A., He, P., Zhu, H. Mechanical characterization of uniaxial compression associated with lamination angles in shale. Advances in Geo-Energy Research, 2024, 13(1): 56-68. https://doi.org/10.46690/ager.2024.07.07