Comparison of Excavation Damage Zones Resulting from Blasting with Nonel Detonators and Blasting with Electronic Detonators

The nonel detonator is a common type of detonator used in drill-and-blast tunnel excavations, while the use of electronic detonators in recent years has also been gaining popularity in complex tunneling conditions (Fu et al. 2012). The delay time of the latter can be arbitrarily set up accurately according to in situ blasting conditions, from a minimum delay time of 1 ms to a maximum delay time of 15 to 16 s. By detonating blastholes one by one by using electronic detonators, the extent and damage degree of the excavation damaged zone (EDZ) of a tunnel can be better controlled. In order to investigate the beneficial effect of blasting by using electronic detonators, the EDZ associated with the drilland-blast excavation of the Renhechang tunnel located in Chongqing in China by using electronic detonators and nonel detonators are measured and compared in this study. The tunnel has an overburden of 25 to 40 m. The field study involves an ultrasonic wave measurement in drill holes at two different tunnel sections separately excavated by using electronic detonators and nonel detonators. The results demonstrate that using electronic detonators can help limit the EDZ development in drill-and-blast tunnel excavations.