Study on stress wave propagation and attenuation in through-jointed rock mass

In western mining construction, the freezing shaft method is employed to penetrate water-bearing fractured rock masses, forming ice-rock composite structures. However, the blast shock waves during construction can affect frozen surrounding rock, posing safety risks. Using the Hopkinson bar test apparatus, we systematically analyzed the propagation and attenuation patterns of post-blast stress waves in frozen rock fracture surfaces. Key findings include: (1) When impact pressure reaches the specimen failure threshold, specimens 0 and 15 exhibit decreasing reflection coefficients (R) followed by increasing transmission coefficients (T) as pressure rises, while specimens 30 and 45 show decreasing R and T values. (2) When incident stress wave intensity is below rock's dynamic compressive strength but above ice's dynamic compressive strength, the ice-rock composite demonstrates three failure modes: compressive, shear, and combined compressive-shear failure, depending on structural surface angle and loading strain rate. (3) The overall weakening effect at structural surfaces significantly outweighs strain rate-induced reinforcement. Notably, specimens with 45° inclination show gradually reduced R value decline but maintain substantial T value decrease, indicating lower sensitivity to stress wave reflection at steep angles compared to transmission effects. This study provides theoretical insights for mitigating disturbance effects in fractured rock masses during freezing shaft construction in cold regions.