Abstract: Fractal dimension is a quantitative description of mesoscopic features of rock, such as fracture, fragmentation and damage; the meso-structure of rock often has a great impact on the macro-strength characteristics. In this paper, the effect of wet-dry cycles on the meso-scale characteristics of altered granite was investigated. First of all, the meso-scale images of altered granite undergone different dry-wet cycles were obtained through SEM test; the fractal dimension of each rock sample was calculated by box dimension method, and the equation of meso-damage evolution based on fractal dimension was established. Secondly, the mechanical properties of altered granite undergone different dry-wet cycles were acquired by uniaxial compressive strength and tensile strength tests in laboratory. Based on the experimental data, the relations between the number of dry-wet cycles and the strength and elastic parameters of rocks, and the relations between fractal dimension and strength and elastic parameters were obtained respectively. Results showed that the increase of the number of dry-wet cycles of rocks led to the decrease of tensile strength, uniaxial compressive strength and modulus of elasticity in macro-scale, and the increase of fractal dimension at mesoscopic level. Poisson’s ratio was not affected. Fractal dimension quantifies the meso-characteristics of rocks and establishes a meso-and-macro-relationship, which can be used as an indicator of measuring the strength characteristics of altered granite.

Key words: altered granite, fractal dimension, rock strength, SEM, MatLab