Experimental study of stress wave propagation and energy characteristics across rock specimens containing cemented mortar joint with various thicknesses

Stability and safety of rock structures are easily influenced by the dynamic disturbance, especially when weak joint planes exist. In order to investigate the filling joint effect on the dynamic response of rock specimens, a series of impact dynamic tests were conducted by a modified split Hopkinson pressure bar (SHPB) system. A sandwich type of sandstone specimens filling with different thicknesses layer of cemented mortar (filling joint) were tested in the study. The results show that the transmission coefficient, dynamic strength and energy absorption all decrease with increasing joint thickness. However, the reflection coefficient, peak strain and joint closure show an opposite variation trend. In addition, the deformation of the cemented mortar joint is the main reason to cause the deformation and final failure of jointed rock specimens. Tensile cracks dominate the fracturing behavior during the dynamic loading, but they have a slight influence on the final failure mode which transforms from localized slabbing to axial splitting failure with the filling joint becoming thicker.