Abstract:

Considering the universal existance of damaged rock mass in the actual environment, the typical sandstone was selected to investigate the creep and saturation induced damage. The damage variable analysis and calculationunder different influence factors were carried out. Based on unloading failure tests on damaged sandstone samples under different influence factors, the morphological characteristics of the unloading failure surfaces were compared and analyzed by using ST400 type 3D surface topography instrument, and the influencing mechanism of creep and saturation induced damage on the morphology of the unloading failure surface was discussed. The damage variable analysis shows that the elastic modulus method can well reflect the damage degree under different influence factors, while the ultrasonic detection method is sensitive to saturation and incapable to describe the damage degree of sandstone after creep and saturation. Morphology characteristic and fractal characteristic of the unloading failure surfaces from specimens with different damage degree show that the creep and saturation damage increases the overall roughness of the unloading failure surface, which makes the dispersion and fluctuation of the failure surface become larger. Meanwhile, the creep and saturation damage results in low roughness and obvious anisotropy of the failure surface and the fractal dimension decreases first and then increases with the damage changes from negative to positive. Compared analysis of two group specimens shows that saturation after creep damage has no significant influence on morphological characteristics of the unloading failure surface, which means that creep damage is the main influence factor.

Key words: rock mechanics, damage variable, 3D morphology scanning, morphology characteristic parameters