Vibration Characteristics and Foundation-Level Response Assessment of Existing Transmission Towers Subjected to Adjacent Railway Tunnel Blasting

Tunnel blasting adjacent to existing transmission towers may induce foundation vibration and transient deformation, affecting the response evaluation of transmission tower foundations. This study investigates the blast-induced response characteristics of three in-service high-voltage transmission towers adjacent to the Langjiafan Railway Tunnel. Field monitoring was conducted at different longitudinal distances to obtain three-component peak particle velocities (PPVs) and dominant frequencies. Site-specific vibration attenuation relationships were established using the Sadovsky empirical model, and a three-dimensional tunnel–rock mass–transmission tower numerical model was developed and validated against field measurements. The results show that the PPVs generally increased as the tunnel face approached the towers, and the vertical component exhibited relatively larger responses under the investigated blasting conditions. The maximum vertical PPVs of Towers No. 1–3 were 0.9563, 1.1253, and 1.5198 cm/s, respectively, corresponding to 38.3%, 45.0%, and 60.8% of the adopted control value of 2.5 cm/s. The dominant frequencies mainly ranged from 20 to 65 Hz in the horizontal directions, while the vertical components exhibited higher-frequency characteristics under certain blasting conditions. The Sadovsky models achieved coefficients of determination of 0.927, 0.923, and 0.903, and the numerical model reproduced the measured vibration attenuation trends with mean relative errors of 12.48–13.22%. The maximum transient differential foundation displacements of Towers No. 1–3 were 0.1064, 0.1947, and 0.1433 mm, respectively. The results indicate that both foundation vibration velocity and transient deformation should be considered when evaluating the response of transmission tower foundations subjected to adjacent tunnel blasting. The findings provide site-specific references for vibration monitoring and blast-induced response control of existing transmission tower foundations under similar underground blasting conditions.