Transmission path of blasting vibration in a cross-tunnel and PPV prediction of the full section of the existing tunnel

In cross-tunnel projects, excessive blasting-induced vibration may threaten the operational safety and structural stability of existing underground structures. Accurate prediction of tunnel blasting vibration intensity is essential for effective vibration control. Based on the Caomaoshan intersecting tunnel project of the Beijing–Zhangjiakou High-Speed Railway, this study combines field monitoring and numerical simulation to investigate blasting vibration propagation characteristics and PPV prediction approaches. First, the applicability of traditional PPV prediction models for the existing tunnel sidewalls is evaluated using field monitoring data. Subsequently, three-dimensional numerical simulations are conducted to reveal the PPV distribution mechanism from the perspective of stress wave propagation. To consider stress wave diffraction caused by the cavity formed during excavation of the new tunnel, the PPV prediction model for the full cross-section of the existing tunnel is modified by introducing a minimum diffraction distance ( R m ). The results indicate that diffraction of waves around the excavated cavity is a primary cause of non-uniform PPV distribution across the existing tunnel cross-section. Taking the USBM equation as an example, the modified model achieves coefficients of determination of 0.924, 0.971, and 0.949 when the new tunnel face approaches( L < 0 m), reaches( L = 0 m), and passes beyond( L > 0 m) the intersection, respectively, representing increases of 23.38%, 20.74%, and 6.33% compared with the original model. These findings demonstrate that introducing R m provides a more accurate representation of effective stress wave propagation paths considering cavity-induced diffraction, thereby improving PPV prediction across the existing tunnel cross-section under different relative positions of the blast source.