关键词: 花岗岩, 风化程度, 分形维数, 波速比, 碎屑特征, 裂缝形态

Abstract: The weakening of physical and mechanical properties of weathered granite often has a great impact on engineering stability. Therefore, it is of great significance to study the failure characteristics of granite with different weathering degrees. Combining the qualitative description of the core characteristics and the quantitative evaluation index of wave velocity ratio, the granite rocks collected from the reservoir area of Wuyue Pumped Storage Power Station in Henan Province were divided into three groups: slightly weathered granite, weakly weathered granite and strongly weathered granite. The fragments generated from granite rocks during uniaxial compression tests were collected, and their quality and scale characteristics were analyzed. Then, the corresponding relationship between fragment fractal dimension and wave velocity ratio was established. Meanwhile, the MATLAB software was employed to calculate the fractal dimension of the cracks on the main rupture surface. The results show that weathered granite rocks mainly produce coarse grain fragments and the proportion of fragments in coarse group gradually increases with the increase of weathering degree. Strongly weathered rocks produce blocky fragments in a small proportion and have a narrow range of the length-thickness ratio, indicating weak dynamic failure characteristics. Besides, their fragment shapes are single and mainly have plate-like structure. With the decrease of weathering degree, the proportions of blocky fragments increase and the dynamic failure characteristics become more apparent. The fractal dimensions of fragments have an increasing trend with the increase of the wave velocity ratio. Compared with the fragment quality, width and thickness, the fragment quantity and length are the main factors affecting the fractal dimension and are also the main parameters reflecting the fractal characteristics of granite with different weathering degrees. Moreover, the crack fractal dimensions of rupture surface for weakly and slightly weathered granite rocks increase significantly with the increase of wave velocity ratio, while for strongly weathered granite rocks there is no obvious change. It implies that the cracks of weakly and slightly weathered granite rocks have a higher degree of self-similarity, more complex structure and require more energy for their initiation and propagation

Key words: granite, weathering degree, fractal dimension, wave velocity ratio, fragment characteristics, crack morphology