Physical modelling of propagation characteristics of blasting stress waves in rock masses with parallel and X-shaped intersecting joints.

During rock blasting in tunnel excavation and mining, the presence of jointed fractures significantly affects the construction safety and stability of surrounding rock masses. To elucidate the effects of joints with different geometric configurations on the propagation behavior and attenuation mechanisms of blasting stress waves in rock masses, this study conducted similar material model tests to construct rock mass models containing parallel joints and X-shaped intersecting joints. Using Fast Fourier Transform and DIC image processing, a systematic comparative analysis was conducted on the effects of the two types of joint structures on the frequency-domain characteristics, attenuation properties, and strain-displacement fields of blasting waves. The results show that joint structures significantly alter the frequency-domain characteristics of blasting stress waves. Based on the concentration of stress wave energy in the low-frequency range (0-200 Hz) in the rock mass model, parallel joints lead to the formation of multiple resonance peaks at 1000-3500 Hz. In contrast, X-shaped intersecting joints induce broadband scattering effects, resulting in dispersed energy distribution across the frequency domain and smoother secondary resonance features. Vibrations in the parallel joint region attenuate slowly and persist for an approximately 12-15 ms longer duration on the basis of 10-20 ms. In the intersecting-jointed region, high-frequency oscillations and rapid attenuation are observed, with significantly stronger energy attenuation capacity compared to parallel joints. Highly concentrated strain occurs in the vicinity of intersecting-jointed fractures, and the markedly enhanced shear strain is prone to initiating crack propagation. This work provides experimental support for blast design under complex geological conditions.