Based on viscous boundary theory, the artificial boundary was implemented in DDA method and well proved with a specific example. Using the modified DDA method, the influence of joint stiffness,joint spacing,weak intercalation thickness, and impedance on elastic P-wave propagation were studied. The results showed that, the difference of transmission coefficient of joint surface between DDA calculation and theoretical solution is very small. The attenuation of elastic P-wave increases with the decrease of joint stiffness. There exists threshold value and critical value for joint space. In different ranges, the wave attenuation law is different. The transmission coefficient of elastic P-wave on interface calculated by DDA method is very close to the theoretical solution. Weak intercalation thickness affects the interference effect of multiple transmission. The attenuation of elastic P-wave increases with the decrease of weak intercalation impedance.
