LAUSR

Control of blasting induced damage zone is one of the important topics in hydropower project construction, and the acoustic test method is commonly used to discriminate the blasting induced damage zone. However, the acoustic test results are usually affected by the geological conditions of the test site. During the traditional process of the acoustic test, water is usually injected into the test hole as a coupling agent. However, when the rock mass is abundant in joints, water leakage will appear, and thus the coupling water is in a flowing state. A large number of measured data indicate that when coupling water is in a flowing state during the acoustic test, the quality of the measured acoustic waveform will be worse than that in still water coupling, especially at the take-off point of the first waveform. The experiment results show that the acoustic waveform deterioration is mainly influenced by low-frequency interference, which is produced by pulsating pressure induced by flowing water. Furthermore, when the acoustic wave data is influenced by low-frequency interference caused by flowing water coupling, the take-off point of the first waveform will be more obvious while the acoustic wave data is filtered with appropriate frequency; as a result, the readability of the data will be enhanced and the accuracy of the acoustic test will be improved.