Dynamic Performance and Stress Wave Propagation Characteristics of Parallel Jointed Rock Mass Using the SHPB Technique

To investigate the effects of joint number on dynamic compressive strength, crushing effect, stress wave propagation, stress wave conversion, and energy evolution of rock masses, SHPB and LS-DYNA were used to conduct impact experiments and numerical simulations, respectively. The results demonstrate that the dynamic strength of a multi-jointed (two- and three-jointed) rock are 11.1 and 25.1% lower, respectively, compared with that of a single-jointed rock. The weak surface near the joint causes the rock mass to crack first. The rock cracking time advances significantly as the joints number increases. The reflection coefficient falls as the number of joints increases, because the wave impedance of the joint differs from that of the rock. The transmission coefficient, however, is exactly the reverse. When the P wave strikes the specimen, the vibration direction of the particles is deflected at the joint, resulting in a shear wave. P waves are reflected and superimposed between joints, increasing the strength of shear waves and resulting in more transverse cracks in multi-jointed rock masses under dynamic loading. Meanwhile, the total energy consumed by a bedrock under dynamic loading is obviously larger than that of joints. However, the total energy absorbed by joints exceeds that of the bedrock when the joints number increases. The results further enrich the dynamic basis of jointed rock masses.