Remote Impact Acoustic Inspection of Structures Using Water Jet Impacts

Abstract We have developed an advanced method for remotely detecting defects in concrete structures using pulsed water jets, offering significant improvements over traditional continuous flow impact echo testing. Unlike the conventional approach, our method utilizes intermittent, high-pressure water jets, which enable more distant and efficient inspections while minimizing water consumption. Notably, the pulsed nature of the water jets makes the testing process less susceptible to wind interference and broadens the excitation frequency range, potentially enhancing defect detection capabilities. In our experiments, we targeted concrete specimens embedded with artificial cavities to simulate common defects, employing a 4 mm diameter nozzle at 1 MPa pressure to release water pulses for 0.01 seconds. The testing distances extended up to 5 meters, demonstrating the method’s effectiveness in detecting 300 mm diameter cavities from a significant range. Defect identification was facilitated by analyzing the acoustic impact signatures through spectrogram visualization, focusing specifically on frequency bands resonating with the defects’ natural frequencies.