Abstract: This study aims to investigate the anisotropic characteristics of phyllite in Maoxian group from the northwest of Sichuan province in China. A series of uniaxial and triaxial compressive tests is conducted on phyllite samples by using the MTS815Teststar rock mechanics testing system. Experimental results show that the large deformation and partial failure generally appear before samples reach half of their peak strengths. However, the occurrences of large deformation or initial dilatancy do not indicate that rock completely loses its bearing capacity. If the targeted support or protection can be applied on surrounding rock in time, rock strength is still strong. Damage dilation is regarded as a typical deformation and failure characteristic of phyllite. Furthermore, it affects lateral deformation more easily than axial deformation. Thus, lateral deformation can reflect rock yield or weakening more sensitively. Results show that the anisotropy of rock strength decreases with increasing water content and confining pressure. Moreover, Young’s modulus and Poisson’s ratio vary with the loading direction and translated-confining pressure. From the obtained results of phyllite at different water contents, the strength of phyllite under dry condition presents the most obvious anisotropic characteristics in uniaxial compressive tests. It is found that the anisotropic ratios of compressive strength are mainly below 0.8. Especially, sericite phyllite exhibits the strongest anisotropy with a ratio of 0.48, and the following anisotropic orders from strong to weak are sericite phyllite, chlorite phyllite, quartz phyllite, and carbonaceous phyllite. Moreover, there are different failure modes of phyllite, which also change with the increase of confining pressure and water content. Shear failure occurred uniformly along the weak planes, which indicates that the anisotropic mechanical characteristics of phyllite are controlled by shear mechanism independently.

Key words: phyllite, mechanical characteristics, anisotropy, dilation, failure mode