Transversely Isotropic Slates Subject to the Compressive Differential Cyclic Loading, Part I: Experimental Investigations

• Published in: Rock mechanics and rock engineering Vol. 57; no. 8; pp. 5609 - 5635
• Main Authors: Song, Z. Y., Zhang, T., Dang, W. G., Hamdi, P., Song, F., Yu, Z. H., Yang, Z.
• Format: Journal Article
• Language: English
• Published: Vienna Springer Vienna 01.08.2024; Springer Nature B.V
• Subjects: Bedding; Civil Engineering; Coupled modes; Cyclic loading; Cyclic loads; Damping ratio; Deformability; Deformation effects; Earth and Environmental Science; Earth Sciences; Energy dissipation; Energy exchange; Formability; Geophysics/Geodesy; Growth rate; NMR; Nuclear magnetic resonance; Original Paper; Phase (cyclic); Phase shift; Residual energy; Slates; Strain; Strain analysis; Unloading; Transversely isotropic rock; Nuclear magnetic resonance; Differential cyclic loading; Phase shift; Rock anisotropy
• ISSN: 0723-2632; 1434-453X
• DOI: 10.1007/s00603-024-03940-4

This article presents an experimental investigation on failure strengths and mechanical responses of transversely isotropic slates under the compressive differential cyclic loading. The tests involve five bedding orientations (0°, 30°, 45°, 60°, 90°) and two loading modes. The tests aim to investigate the coupled influence of the distinct loading/unloading rates and bedding orientation on the anisotropic characteristics, incl. the deformability, energy dissipation, damping ratio, phase shift and failure patterns. The results show that both loading modes and bedding angles have impacts on the mechanical responses of slates. Specifically, it is observed that rapid loading and slow unloading result in a higher growth rate of peak/residual strain versus cycle number as well as more intensive energy dissipation, and correspond to more significant phase shift. The influence of bedding angles on energy dissipation and strain is less pronounced compared to the effects of differential cyclic loading. The nuclear magnetic resonance was used to analyze the T2 spectra of the failed samples with different bedding angles. Highlights Rapid loading and slow unloading tend to intensify the phase shift at peak stress, while their effect on minimum stress remains unpronounced. Rapid loading and slow unloading tend to cause larger energy dissipation under different bedding angles. The modified Jaeger's plane of weakness model can well capture rock strengths across varying bedding angles when subjected to differential cyclic loading.