Abstract: The structural plane of rock mass shows obvious anisotropy, which directly influences the deformation characteristics, mechanical properties and seepage characteristics of rock mass. It is significant to conduct the anisotropic quantitative analysis of the structure surface. In this paper, the anisotropy characteristics of different genetic structure planes are analyzed by the common structural surface quantization parameters (joint roughness coefficient JRC, the average joint angle θ, and fractal dimension DB), and their influences on the shear mechanical properties are also studied. The results show that in the tensile structure plane, the values of JRC and θ along the direction of splitting are larger than the values of these parameters perpendicular to the splitting direction and fluctuated slightly with the change of the angle. DB fluctuated largely in the diagonal direction, and its value is related to profile length. In shear structure plane, the values of JRC and θ parallel to the splitting direction have no significant differences from those perpendicular to the splitting direction. However, DB changes greatly in the diagonal direction. When θ and DB are used to evaluate the anisotropy of the structure plane, there is no obvious difference in anisotropy coefficients of splitting fracture plane and shear fracture plane. While, when JRC is used as evaluation parameter, the anisotropy coefficient is quite different, which could better reflect the different characteristics of different structural planes. The peak shear load and normal displacement of shear fracture plane are higher than those of splitting structure plane. The shear displacements of the two structural planes are similar when the dilation angle reached the peak value, and the aperture distribution of shear fracture structural plane is relatively concentrated and generally larger. The aperture distribution splitting fracture plane is more dispersed.

Key words: structure plane, splitting, shear, anisotropy, mechanical characteristics