Through the RMT-150C testing system

artificial concrete joint samples are employed to study the shearing stiffness and failure mode for rock joint under different shearing deformation velocities

undulation angles and normal stresses. It is suggested that the failure modes of joint samples are dominated by the undulation angles. Under small undulation angle

the joint samples are in abrasion failure mode

while under high undulation angles

the joint samples are in snip failure mode. The failure modes of joint sample are also influenced by the normal stress and shearing deformation velocity. It is also reported that the shearing stiffnesses of joint samples increase with the increasing shearing deformation velocities and undulation angles; and the rising rates tend to decrease with the increment of shearing deformation velocities. As well

the shearing stiffnesses of joint samples linearly increase with the increasing normal stresses. The shear stiffness formula is further presented to consider the effect of shearing deformation velocity and undulation angle. Based on the experimental results

the regression results for the formula are also conducted.