English：

Blasting excavation of new tunnels can generate instantaneous impact loads and stress wavepropagation that may affect the stability of underlying existing tunnels. In this study, the Guzhang Tunnelovercrossing the Luoyixi Tunnel on the Yongji Expressway was taken as a case study. A three⁃dimensionalnumerical model was established using FLAC3D to investigate the settlement and vibration responses ofthe existing highway tunnel during the blasting process of the new tunnel. The results indicate that thesettlement behavior of the existing tunnel differs under various crossing conditions. During the firstovercrossing stage, the intact and stiffer surrounding rock leads to smaller settlement, whereas in thesecond overcrossing stage, the reduced stiffness of the previously excavated right⁃line overburden resultsin greater settlement. Under the same working condition, uplift deformation occurs at the left⁃line tunnelcrown while the right⁃line tunnel exhibits settlement, suggesting a spatially asymmetric disturbance effectinduced by blasting. Under a blasting load of 25. 9MPa, the maximum settlement of the existing tunnelfloor is approximately 1. 35mm, and the peak vibration velocity at the crown reaches 3. 16cm / s, both farbelow the permissible limits specified in relevant codes. These findings demonstrate that the overallstructural stability remains satisfactory.