Abstract: To investigate the shear characteristics of limestone joint surfaces with different water-bearing states under normal dynamic loading, the self-made KYZW-50D rock dynamic shear coupling test system was used to conduct dynamic shear tests with different water contents and normal loading frequencies. Additionally, three-dimensional morphology scanning tests were conducted on the sheared joint surfaces to examine the effects of water content and normal dynamic loading frequency on shear strength and morphology parameters. The findings indicate that: (1) The shear strength of the limestone joint surface exhibits a logarithmic decline as normal loading frequency increases. The deterioration of the shear strength gradually decreases and stabilizes when the normal loading frequency exceeds 2 Hz. (2) With constant initial normal stress, an increase in water content results in a gradual decrease in shear strength and morphology parameters of joint surfaces, along with an overall increase in deterioration degree and a reduced difference in deterioration between constant normal stress and dynamic normal stress conditions. (3) Based on Barton's shear strength equation, a shear strength equation considering the effects of normal loading frequency and water content was established. Validation showed it more accurately reflects shear strength deterioration of joint surfaces with different water contents under dynamic normal stress. The relevant methods and conclusions provide a theoretical basis for analyzing the stability of jointed rock bodies under dynamic disturbance conditions.

Key words: joint surface, water content, dynamic normal load, shear strength, joint surface morphology