Experimental evaluation of the modified displacement discontinuity method considering the thickness of filled joints

ABSTRACT The modified displacement discontinuity method (M-DDM) was experimentally evaluated, taking into account joint thickness for wave propagation in filled joints. First, M-DDM considering joint thickness was introduced to investigate the wave propagation in filled joints by adding the effective stiffness that describes the dynamic deformation properties of filled joints. Subsequently, the pendulum impact tests were conducted to examine the wave propagation in filled joints using gypsum, sand, and clay as filling materials. The effect of the filling thickness of joints on transmission coefficients was investigated. Finally, a comparison was conducted to evaluate the accuracy of M-DDM by contrasting its results with those obtained from the experimental study. The findings indicate that the joint-filling materials and thickness have a significant effect on the stress reflection and transmission at the filled joint. As the thickness of the filling material increases, the transmission coefficient shows a gradual decline. In addition, the transmission coefficients obtained from the pendulum impact test and M-DDM consistently align for wave propagation through filled joints. Furthermore, M-DDM consistently maintains a small prediction error for the transmission coefficient as the filling thickness increases. Therefore, M-DDM is capable of efficiently investigating the wave propagation through filled jointed rock masses with various filling materials.