Experimental study on the shear mechanical behaviors of a rough rock joint surface under dynamic normal load boundary condition

To explore the load-bearing characteristics of the rock joints under seismic loads，the shear experiments about the mechanical behaviors of a rough joint surface under the dynamic normal load stress were carried out. The influence of the amplitude and frequency of the dynamic normal load on the intensity parameters，morph parameters and failure characteristics of the joint surface were obtained. The results show that：(1) Increasing the dynamic load amplitude results in a linear decrease of 48.27% to 55.59% in the peak shear strength. The dynamic load frequency has less impact on the peak shear strength. In the stable residual stage，the shear stress amplitude width increases linearly by 1.24 to 2.83 times with increasing the amplitude，and the dynamic loading frequency increases from 0.2 Hz to 0.5 Hz，resulting in a rapid decrease of 36.28% to 40.61% in the shear stress amplitude. This decline continues gradually after the frequency exceeds 0.5 Hz. (2) The shear stiffness in the pre-peak stage is a normal stress-dependent. And，both the amplitude and frequency of the dynamic normal load decrease the shear stiffness in the pre-peak stage and dilatancy in the post-failure stage. (3) A significant phase shift between the shear stress and normal stress occurs. The phase offset decreases with the increase of the amplitude and frequency of the dynamic normal stress. When the frequency reaches 2.0 Hz，the phase shift becomes negligible. (4) When the frequency is below 0.5 Hz，the proportion of the joint surface wear area increases sharply by 36.10% to 69.37%. Conversely，when the frequency exceeds 0.5 Hz，the wear area proportion shows an approximately linear increase of 5.17% to 10.18%. © 2024 Academia Sinica. All rights reserved.