Test and DEM study on cyclic shear behavior of sand–irregular concrete interface under dynamic normal loading

To explore the dynamic response of sand–irregular concrete interface, a series of cyclic direct shear tests were conducted under dynamic normal loading, with different joint roughness coefficient (\(\it {\text{JRC}}\)) and dynamic normal loading frequency. DEM models were developed to analyze its microscopic behavior. Research results indicate that there was a critical \(\it {\text{JRC}}\) that maximized the interface shear strength. Maintaining a constant frequency of dynamic horizontal loading, changing the dynamic normal loading frequency resulted in changes in the shape of the shear stress–displacement hysteresis loops. The increase in dynamic normal loading frequency led to an increase in energy dissipation coefficient, which ranged from approximately 0.85 to 0.95. Energy introduced into the system by shearing was predominantly dissipated by internal mechanisms, mainly through slip and rolling slip. Dynamic horizontal loading would result in a decrease in the average force chain length and strength. As shearing, the anisotropy of the contact normal direction and tangential contact force of specimens significantly decreased. When the specimens were at shear stress reversal point, the anisotropic orientation of contact normal direction, normal contact force, and tangential contact force rotated toward the shear direction, and the rotation angle increased with the increase in \(\it {\text{JRC}}\).