Abstract: In this study, the uniaxial compression test and Brazilian splitting test were carried out on Silurian silty slates in northwest Hubei province to investigate their mechanical and anisotropic properties. The anisotropic mechanical properties and deformation failure modes of specimens were analysed under different loading conditions, and the corresponding mechanisms of different failure modes were revealed. Meanwhile, the numerical analysis was used to study failure modes and mechanical mechanisms of slate slopes with different angles of bedding planes. The results showed that bedding planes in silty slates were weak surfaces that affected mechanical properties of rock mass, resulting in obvious anisotropic characteristics of the silty slates. Under the uniaxial compression condition, the deformation of silty slates were easier in the direction of the vertical bedding plane than that of the parallel plane, and their deformation was more significant. The failure mode of the specimen was the vertical splitting tensile failure when the direction of the parallel plane was loaded, while the failure mode was the splitting shear failure cutting the bedding planes when the direction of the vertical plane was loaded. The anisotropy of measured mechanical parameters was relatively apparent. Under the action of splitting load, the failure modes of silty slates mainly included the tensile splitting failure and shear failure along the bedding plane. The obtained tensile strength was the largest in parallel bedding plane direction and was the smallest in the vertical bedding plane direction. The tensile strengths in both directions were lower than the compressive strengths. As the tensile strength between bedding planes was extremely low, tension-split failure or tension-shear failure was easily caused by the splitting load that intersected with the bedding plane at a small angle. Hence, the tension failure or tension-shear failure along bedding planes should be avoided as far as possible in practical engineering. The dip directions and angles of slates have great influences on failure modes and mechanics of slates slopes, which should be considered in the protection and treatment of rock slopes. Therefore, the results provide significant references for the protection and treatment of rock slopes, design and construction of other rock engineering projects in the distribution area of silty slates.

Key words: rock mechanics, silty slate, uniaxial compression test, Brazilian splitting test, mechanical property, anisotropy