A new cap with a slider structure was implemented to triaxial testing apparatus for measuring elementary behaviors of an anisotropic material. Top of a cylindrical specimen could displace to perpendicular directions against the loading axis and frictionless boundary conditions were given by the cap. Using this apparatus, six small strain tensor components of tuff including bedding plane were investigated during both uniaxial and triaxial compression tests. The results of uniaxial tests, using

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... o specimens sampled in parallel and perpendicular orientations to the bedding planes, demonstrated tangent Young's modulus in the bedding direction is 1.5 times larger than that in the perpendicular direction. The anisotropy of Tage tuff assuming transversely isotropic elasticity is identified via proposed method by a single triaxial test using each specimen with inclined bedding plane at 15° or 45°. The results demonstrated that the dominant orientation of the anisotropy agreed well with that of the bedding plane, and anisotropic stiffness values obtained from a single triaxial test were close to those by uniaxial tests.