Experimental Study on Anisotropic Properties of Silurian Silty Slates

The objective of this study was to investigate the mechanical and anisotropic characteristics of slates in Northwest Hubei of China. For this purpose, uniaxial compression test and Brazilian splitting test were carried out on Silurian silty slates so as to analyse the mechanical and anisotropic characteristics as well as deformation and failure modes of slates under different loads. Meanwhile, the mechanical mechanisms of different failure modes were revealed. Research results showed that bedding planes in silty slates are the weak planes influencing the mechanical behaviours of rock masses so that silty slates present obvious anisotropy. Under uniaxial compression conditions, silty slates were more easily to be deformed more remarkably in the direction perpendicular to bedding planes in comparison with those in the direction parallel to bedding planes. When loads were applied along bedding planes, it was found that the specimens suffered from vertical splitting tension failure, which was essentially the instability of compression members; when the loading direction was perpendicular to bedding planes, splitting shear failure cutting through bedding planes occurred to specimens. The mechanical parameters measured also presented apparent anisotropy. Under the effect of splitting loads, silty slates were primarily subjected to tension splitting failure and shear failure along bedding planes. The measured tensile strength was shown to be the maximum in the direction parallel to bedding planes, while that perpendicular to bedding planes was the minimum. However, both the tensile strengths in these two directions were less than the compressive strengths. The tensile strength among the bedding planes was so low that tension splitting or shear failure easily happened along bedding planes when the splitting loads applied formed a small angle with bedding planes. Therefore, tensile failure among bedding planes and tensile-shear failure along the bedding plane are supposed to be avoided in practical engineering. This study provides a theoretical basis and technological base for the protection and treatment of rock slopes and other rock engineering design and construction in silty slate regions.