# Experimental Study on Mechanical Properties of Anisotropic Slate under Different Water Contents
## 5 Conclusions  
This study conducts uniaxial and triaxial compression experiments on weathered slates from the Proterozoic Barxi Group in Changsha City, China. The analyses of stress-strain curves, deformation and failure modes, and mechanical parameters revealed the anisotropic characteristics of slate under varying water contents, bedding angles, and confining pressure conditions. The following conclusions can be drawn:  
1. Under uniaxial compression, the compaction stage of microfractures in slate is inconspicuous. The subsequent stable development stage of microelastic fractures is brief. When peak strength is reached, the stress sharply decreases, exhibiting characteristics consistent with brittle fracture. With applied confining pressure, slate compactness increases as confining pressure rises, restricting fracture development under loading and decelerating the failure process. This is macroscopically observed as a reduction in brittleness and an increase in plasticity. 2. As water content increases, certain minerals dissolve along the bedding direction, increasing the number and size of microfractures and gradually reducing the peak strength of the sample. In this scenario, the bedding plane deteriorates more than the matrix, making the slate more susceptible to shear failure along the bedding direction. The yield stage becomes more pronounced in the stress-strain curve, and the post-peak stress reduction is slower. 3. The failure mode of the slate strongly correlates with the bedding angle. Samples at 0 deg typically exhibit splitting shear failure through the bedding plane; those at 30 deg primarily experience shear failure through the matrix; samples at 45 deg demonstrate both failure along the bedding plane and partial shear failure along it; all failure  
Figure 16: Cohesive force and internal friction angle of slates with different bedding angles: (**a**) dry state, (**b**) natural state, and (**c**) saturated state. modes of the 60\({}^{\circ}\) samples involve shear failure along the bedding plane; the 90\({}^{\circ}\) samples predominantly fail by splitting tension. 4. As the bedding angle increases, the compressive strength of the slate displays a U-shaped trend, with higher values at both ends and a lower value in the middle. Incorporating the anisotropic parameter, the Hoek-Brown formula more accurately predicts slates' uniaxial and triaxial compressive strengths with different bedding angles. The anisotropic properties of slate compressive strength vary with confining pressure and water content: They diminish as confining pressure compacts the microfractures between weak slate bedding planes and intensify as water infiltrates fractures and pores between beddings, exacerbating deterioration responses. The slate in this study exhibits medium to high anisotropy. 5. Currently, two trends are observed in the variation of elastic modulus: one is proportional to the bedding angle, and the other follows a U-shaped curve. The elastic modulus of slate in this study forms a U-shaped pattern with the bedding angle; however, the change is minor between 0\({}^{\circ}\) and 60\({}^{\circ}\) and becomes pronounced at 90\({}^{\circ}\). Utilizing the generalized Hooke's Law to describe the curve between elastic modulus and bedding angle and comparing \(R^{2}\) under various water contents and confining pressures, it is evident that a lower degree of anisotropy in the elastic modulus indicates better agreement between the calculated and actual values. 6. The Poisson's ratio and internal friction angle of slate remain relatively unchanged at different bedding angles, while cohesion follows a U-shaped pattern with increasing bedding angle. All three are influenced by water content, notably in Poisson's ratio value, the trend of internal friction angle variation, and the range of cohesion changes. These aspects exhibit significant differences under varying water contents. Conceptualization, methodology, software, writing--original draft preparation, X.Y. and J.L.