Acoustic and Electromagnetic Wave Methods for Early Detection and Evaluation of Shallow Cavities Beneath Structures Academic Article in Scopus uri icon

abstract

  • This study developed methods that use acoustic and electromagnetic waves for the early detection and characterization of cavities beneath structures. The model cavities were simulated using an acrylic crate filled with dry sand. Top plates fabricated from various materials (acrylic, wood, and concrete) were placed on the sand surface, and a controlled sand disposal valve facilitated incremental cavity formation (0¿1500 g). Acoustic wave tests employed a microphone to measure the waves generated by hammer impacts using interchangeable hammer tips (aluminum, plastic, and rubber). Electromagnetic wave tests utilized an insulated wired probe to systematically measure the electromagnetic waves and reflections of the three plate materials. The experimental results showed a strong correlation between pitch frequency and cavity size. Early cavity formation caused significant transitions in the pitch frequency, which were influenced by the plate material, thickness, and tip properties. Wavelet analysis demonstrated high-frequency attenuation and increased prominence of lower frequencies as the cavities grew in size. Electromagnetic waveform analysis revealed a critical transition from early to open cavities at 70 g of sand disposal, showing reduced sensitivity to further cavity growth. Both the acoustic and electromagnetic responses were sensitive in the early stages and gradually converged as the cavities grew. This paper suggests that acoustic and electromagnetic responses are effective indicators of early cavity formation. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2025.

publication date

  • January 1, 2025