ABSTRACT
The effect of Dynamic Normal Load (DNL) on the direct shear behavior of planar joints has been investigated using a dynamic direct shear box device. The shear tests were investigated under different shear velocities, vertical impact frequencies, vertical impact amplitudes and normal load levels. Lab test results show, that the shear force and dynamic friction coefficient show cyclic behavior. Two significant time shifts between peak normal force and peak shear force with peak shear force delay as well as between peak normal force and peak friction coefficient with peak shear force delay are observed. The peak value of dynamic friction coefficient is nearly identical with the static friction coefficient. The minimum value of the dynamic friction coefficient may increase or decrease depending on velocity-frequency (VF), velocity-amplitude (VA) and velocity-frequency-amplitude (VFA) parameters. Finally, a new shear strength criterion is proposed for a planar joint under DNL conditions.
