Piezoelectric-based damage-depth monitoring method for underwater energy-relief blasting technique

Abstract

Owing to the complex geological conditions and strict excavation shaping and damage control requirements in some underwater engineering applications, the development of a suitable blasting excavation technique has become one of the most difficult technical challenges. The application of Energy-Relief Blasting (ERB) technology to underwater drilling and blasting was first proposed, and a new non-destructive damage assessment method for underwater blasting was also developed. To verify the feasibility of ERB in underwater blasting, two comparative underwater drilling blasting experiments at a depth of 40 m were performed in a water-medium explosion vessel. A pair of piezoelectric ceramic transducers as actuators and sensors to emit and receive the acoustic wave signals, respectively, and thus evaluate the blasting damage induced in concrete specimens. A damage index was defined based on the processed data. The experimental results demonstrated that the ERB technique can effectively control blasting-induced damage in the bedrock. For the specimen with conventional blasting, the depth of damage index greater than 92% is 16 cm, while that of energy-relief technique is only 12 cm, which is 25% less than that of conventional blasting. The experimental results also showed that the active sensing method based on piezoelectric transducers combined with the signal processing method based on the transmitted energy can be used to monitor and quantify the damage induced in the rock mass by underwater drilling blasting.