Tunnel Blasting Adjacent to Existing Tunnel and Its Safety Technology

The newly-built tunnel is located in urban area of Quanzhou, with lots of buildings around, overhead crossing with the existing highway Daping Mountain Tunnel, and the min net distance between the vault of the newly-built tunnel and the bottom of the existing highway tunnel is 5.50 m. The newly-built tunnel is parallel to the existing motor vehicle tunnel, and the min horizontal distance between them is 8.50 m. The blasting digging with lower heading fluting method at first and then the complete enlarging in three steps were introduced. Through on-site monitoring and referring to the max velocity of rock damage, the blasting vibration monitoring and blasting control technology of cross tunnels with min net distance formed in space, and parallel tunnel projects with small net distance formed on planes were studied, and the smooth-surface blasting, blast hole water-pressure blasting, millisecond priming net for single hole blasting once each time point and blasting safety control technology were analyzed and disserted. Through monitoring for wall rock steadiness, blasting vibration and information construction of existing tunnel, blasting vibration was checked, blasting parameters and net were adjusted further according to vibration velocity values tested in each measuring point and real conditions observed, thus to control the particle vibration velocity within safety range, and to enable the tunnel in progress to pass through smoothly at the same time the safety and normal operation of existing tunnel was ensured.