Tunnel boring machine vibration characteristics and dynamic disturbance-induced failure mechanisms of surrounding rock in deep tunnels

A rockburst is a dynamic disaster induced by excavation and multi-source dynamic disturbances, characterized by the sudden release of accumulated elastic strain energy in deep engineering rock masses, leading to the bursting and ejection of surrounding rock. In line with the national strategy of building a strong transportation network, field measurements were conducted to capture the vibration characteristics of key tunnel boring machine (TBM) components and the surrounding rock during the construction of a deep-buried TBM-driven railway tunnel. The TBM vibration exhibits a significant surging characteristic, with particularly pronounced vibrations at the shield tail. The measured vibration acceleration ranges from −10g to 10g. At the thrust shoe, the primary vibration direction is parallel to the tunnel axis, with a vibration velocity of 1.5–2.5 cm/s and a frequency of 25–35 Hz. As the distance from the tunnel face increases, the peak particle velocity (PPV) and peak particle acceleration (PPA) of the surrounding rock exhibit a general attenuation trend in the axial, radial, and vertical directions. Accordingly, true triaxial tests on high-pressure hard rock under wide low-frequency disturbances were conducted to examine the effects of TBM low-frequency disturbance on the mechanical properties and disturbance-induced damage behavior of granite. The results demonstrate that the disturbance strength of granite decreases as the stress amplitude increases. For the area affected by the TBM thrust shoe, the disturbance strength increases with both frequency and minimum principal stress. Furthermore, low-frequency disturbance applied in the direction of the minimum principal stress promotes the development of tensile fractures, thereby reducing the bearing capacity of the rock.