The development of complex stress paths tailored to realities of underground gas storage in laboratory to obtain basically mechanical parameters of surrounding rock for assisting in reservoir design and maintenance, has drawn increasing attention in the geotechnical community. However, existing studies are limited, and the effect of stress paths and unloading rates on rock’s deformation and fracture mechanism are not well understood. In this study, four typical stress disturbance forms, including monotonic compression (Stress path Ⅰ), unloading confining pressure (Stress path Ⅱ), cyclic loading and unloading (Stress path Ⅲ) and multi-level fatigue loading (Stress path Ⅳ), were applied to marble. The results showed that the peak strength of the marble generally followed the sequence of stress path Ⅳ > path Ⅰ = path Ⅲ > path Ⅱ, and unloading rate significantly affects post-peak mechanical properties. X-ray CT images and macroscopic failure patterns revealed that the marble under the action of stress path Ⅰ, path-Ⅱ (low unloading rate), and path-Ⅲ showed a single shear crack, under stress path-Ⅱ (high unloading rate) exhibited an X-conjugate shear crack and under stress path-Ⅳ presented obvious point-like shear band cracks. In addition, quantitative analysis of the internal cracks showed that the degree of fracture is negatively correlated with the peak strength and strain. Ultimately, JRC and scanning electron microscope observation of fracture surfaces demonstrated that differences in the mode of input and release of elastic energy determine the damage fracture mechanism of marble. The findings of this study provide scientific evidence for the stability of underground cavern gas storage facilities during project operation.
Li et al. (Mon,) studied this question.