Considering the effect of joint mass on the propagation of stress waves

this study derived formulas for the transmission and reflection coefficients of harmonic waves through the thick viscoelastic joints based on the displacement function of waves. The correlation coefficient of waves was used to describe the waveform changes of the wavelet through viscoelastic joints. Then

we discussed the applicable conditions of a simplified displacement discontinuity model with thick viscoelastic joints. When the correlation coefficient of transmission wave was 0.9

which was calculated by the thick viscoelastic joint model and the displacement discontinuity model

the corresponding thickness of the joint was defined as critical thickness. It was found that there was little impact of the impedance ratio between the rock mass and joint on the critical thickness. The relationship between the critical thickness and the centre frequency followed a negative exponential law. Meanwhile

the larger incident angle was

the lesser impact of centre frequency on critical thickness was. The field tests showed that when the thickness of the joint was 0.03 m

mechanical parameters were extremely close to the results calculated by the thick viscoelastic joint model and the displacement discontinuity model. With the increase of the joint thickness and the centre frequency of the wavelet

the deviation of calculated results using the displacement discontinuity model was larger

which was consistent with the results of theoretical analysis.