## 7 Conclusions  
In this paper, triaxial monotonic loading and triaxial incremental cyclic loading and unloading tests were conducted on shale with three confining pressures and five \(\theta\). Analysis of the anisotropic characteristics of the shale mechanical behavior, AE activity, and energy evolution were analyzed, revealing the mechanism of shale anisotropy weakening. The main conclusions are as follows:  
(1) As the \(\theta\) increases, the compressive strength and elastic modulus of shale first decrease and then increase. The confining pressure and incremental cyclic loading and unloading reduce the anisotropy in the compressive strength and elastic modulus. Compared with triaxial monotonic loading, the compressive strength of shale with \(\theta\) of \(0^{\circ}\) and \(90^{\circ}\) decreases under triaxial incremental cyclic loading and unloading, while the compressive strength increases at \(\theta\) of \(45^{\circ}\) and \(60^{\circ}\). The compressive strength of shale with a \(\theta\) of \(30^{\circ}\) is essentially unchanged. The average ratio of plastic strain to total strain for shale with a \(\theta\) of \(60^{\circ}\) is higher after each loading and unloading cycle than it is for shale with other \(\theta\), indicating that irreversible deformation is more likely to occur in shale with a \(\theta\) of \(60^{\circ}\). (2) Under two loading conditions, the failure modes of shales with \(\theta\) of \(0^{\circ}\), \(30^{\circ}\), and \(90^{\circ}\) are similar, while the failure modes of shales with \(\theta\) of \(45^{\circ}\) and \(60^{\circ}\) differ significantly, as evidenced by the lower degree of involvement that the lower bedding planes have in shale crack evolution under incremental cyclic loading and unloading conditions. In particular, shale bedding planes with a \(\theta\) of \(60^{\circ}\) are more involved in crack evolution than any of the other \(\theta\) conditions. (3) The cumulative ringing number and AE \(b\)-value of the shale show a trend of first decreasing and then increasing as the \(\theta\) increases. As the number of cycles increased, the Felicity ratio gradually decreased, and shale damage accumulated, mainly as the result of small-scale cracks. (4) The total energy density \(U_{0}\) of shale with the same \(\theta\) increases with the confining pressure. For the same confining pressure, \(U_{0}\) generally shows a tendency to first decrease and then increase as the \(\theta\) increases. The minimum value is observed at a \(\theta\) of \(60^{\circ}\). Based on the evolution model of shale elastic energy density, it was found that under constant confining pressure, an increase in the \(\theta\) will lead to the parameter \(m\), which reflects the accumulation rate of elastic energy density, showing first decrease and then increase. When the \(\theta\) is \(60^{\circ}\), the minimum value is reached. When the \(\theta\) is the same, the value of m increases with the confining pressure. (5) The anisotropy of shale is closely related to its failure mode and is the main control factor. The main mechanism by which cyclic loading and unloading weakens the anisotropy of shale is to change the failure mode and main control factor of shale with a \(\theta\) of \(60^{\circ}\), rendering it closer to the failure mode and main control factor of shale with a \(\theta\) of \(0^{\circ}\)  
**Author Contributions:** Conceptualization, S.Z. ; methodology, Q.Y. and F.C. ; software, Q.Y. ; validation, Y.C. ; formal analysis, Q.Y. ; investigation, Y.C. ; resources, Y.C. ; data curation, Q.Y. ; writing--original draft preparation, Y.C. ; writing--review and editing, S.Z. ; visualization, F.C. ; supervision, S.Z. ; project administration, Y.C. ; funding acquisition, S.Z. All authors have read and agreed to the published version of the manuscript. **Funding:** This research was funded by the Geological Research Project of Bureau of Geology and Mineral Exploration and Development Guizhou Province of China (Grant No.