Abstract: The special joint network of columnar jointed rock mass makes its anisotropy significant, and accurately understanding its deformation and strength characteristics are crucial for engineering safety. Based on the natural structure of columnar jointed rock mass, quadrangular, pentagonal and hexagonal prism columnar jointed rock mass specimens with different dip directions and dip angles were manufactured by using gypsum and other materials. Uniaxial compression tests were carried out to study the influence of cross-sectional shape, dip direction and dip angle on the anisotropic characteristics. The typical failure modes and the mechanisms of columnar jointed rock mass were summarised in accordance with the final appearances of specimens. The empirical equations were adopted to estimate the strength and deformation of the columnar jointed rock mass. The results show that the cross-sectional shape mainly affects the deformation and strength parameters of the specimens with different dip directions, but has little effect on the anisotropy of the specimens with different dip angles. The anisotropy of quadrangular, pentagonal and hexagonal prism columnar jointed rock mass are orthotropic, orthotropic and quasi-transverse isotropic, respectively. The final appearances of specimens present four typical failure modes, and the cross-sectional shape mainly affects the failure mode of the specimens with different dip directions. Furthermore, the calculated results of the proposed empirical equations are in good agreement with the existing results, and have high engineering value.

Key words: cross-sectional shape, columnar jointed rock mass, uniaxial compression test, anisotropy, dip direction, dip angle