石材裂纹扩展分形特性

 利用楔形劈裂试验系统观测石材裂纹起裂与扩展，利用应变片系统量测出试件在不同加载速率下裂纹尖端附近裂纹扩展速度的分布及其分形特性。所得结果如下：在考虑不同加载速率下，得到在静态或准静态加载条件下试体的断裂韧性基本上变化不大；但加载速率愈快，裂纹扩展实测平均速度愈高。考虑分形特性，在相同加载速率条件下，所得分形维数越大，则分形裂纹速度也越大，这与理论推导是相符的；分形维数与相关参数(断裂韧性、加载速率)的关系，在静态或准静态加载下近似为一个常数关系。

FRACTAL CHARACTERISTICS OF CRACK PROPAGATION IN ROCK SLABS

A wedge loading compact tension system was used in this study to investigate the phenomenon of crack propagation in rock slabs. A high-resolution crack-strain-gage system was used to measure the velocity of crack propagation. The proposed experimental procedure is able to determine the crack velocity，fractal dimension and fracture toughness of the test specimens. This study finds that under different static loading rates，the fracture toughness of the rock specimen remains constant. However，increasing loading rate will result in an increase of measured average crack velocity. This study also finds that under the same loading rates，increasing fractal dimension will result in an increase of fractal crack velocity which is in full agreement with the theoretical prediction. Under the condition of the static loading，the relationship between the fractal dimension and the related parameter(fracture toughness，loading rates) is essentially constant.