Abstract:

 During the construction and operation of storage reservoirs, the complex stress path plays a crucial role in controlling the damage to the surrounding rock. However, the current study of surrounding rocks lacks a comprehensive consideration of stress paths, especially in terms of the principal stress axis rotation. In this research, a test on rock principal stress axis rotation was conducted using the rock torsion shear apparatus, and the stress field at the fracture tip under stress rotation was analyzed employing fracture mechanics theory. The findings suggest that stress rotation increases the tensile stress at the fracture tip, accelerates fracture propagation, and leads to a notable decrease in rock strength. A methodology for characterizing damage evolution considering stress rotation is proposed based on these findings. Once the maximum differential stress exceeds the first cracking stress, the rotation angles in each direction of the principal stress axis are summed to obtain the cumulative effective rotation angle. This angle is then used to delineate the excavation damage zones (EDZs) based on its variation with depth. The spalling zone is identified using the maximum depth of the damage zone and the range of differential stress that exceeds the second cracking stress. The method integrates the amplitude and rotation angle of the principal stresses to offer a more comprehensive response to the surrounding rock damage evolution mechanism. The validity of this approach is confirmed through a comparison between the numerical model of the Mine-by tunnel and the monitoring data. This study provides novel insights into the damage mechanism of surrounding rock and the prediction of the surrounding rock damage range.

Key words: stress path, excavation damage zone(EDZ), granite, crack initiation stress, stress rotation