Shear Characteristics and Failure Mechanism of Rock Joint Subjected to Dynamic Normal Load: Experimental and DEM Analysis

The deformation and stability of jointed rock masses are significantly influenced by dynamic loads. To investigate the shear properties of rock joint subjected to dynamic load, a series of laboratory and numerical simulation shear tests were conducted under dynamic normal load (DNL) boundary condition. The results show that under DNL condition, the response of shear stress changes lag behind the dynamic normal stress, and this time shift correlates positively with the dynamic load amplitude. Furthermore, the influence of dynamic normal load on the peak shear strength has either enhanced or weakened effects, and this effect depends on the dynamic load parameters and the morphology characteristics of the joint. The dilation is confined by the dynamic normal load more significant, which accelerates the initiation of cracks and the development of shear bands. This confinement alters the failure mode of low inclination angle joint, shifting from dilation to shear failure asperities along the base, and accelerates the shear process to enter the stable sliding stage. Acoustic emission b value indicates that larger fractures develop at relatively low shear stress levels; the RA-AF analysis suggests that dynamic load enhances the proportion of tensile cracks. The numerical simulation indicates that the dynamic load facilitates the concentration of contact force in the normal direction, and it is observed that the number of microcracks escalates with an increase in the amplitude of the dynamic load. A predictive model for peak strength of joint under DNL condition is developed, demonstrating a satisfied predicting accuracy. • A series of laboratory and numerical simulation shear tests were conducted to investigate the shear properties of rock joint under DNL condition. • The response of shear stress changes lag behind the normal stress, and this time shift correlates positively with the dynamic load amplitude. • The peak shear strength has either enhanced or weakened effects, and this effect depends on the dynamic load amplitude and joint morphology. • A predictive model for peak strength of joint under DNL condition is developed, demonstrating a satisfied predicting accuracy.