Data acquisition method and the effectiveness of multichannel analysis of surface waves for defect detections on small earthen dams

Abstract

For small earthen dams, the stability and performance depend heavily on the leakage caused by various reasons, such as aging and lack of maintenance. The effective assessments of these dams are crucial prior to the possible engineering interventions. To this end, a field investigation was conducted to explore the effectiveness of multichannel analysis of surface wave (MASW) method in the detection of leakage zones in small earthen dams. A new method based on the updating strategy of subarrays was designed and used to acquire the surface wave data. The acquisition efficiency and dispersion features of the collected data were analyzed in details. The S-wave velocity inversion imaging of the target dam was also discussed. The results show that the newly designed method allows us to acquire data in a high efficiency. The method is expected to consume 48% shorter time than the commonly used one. The analysis reveals that the dispersion energy and dispersion curves of acquired surface waves are influenced by the subarray lengths. The effect is reflected in the distribution of the fundamental mode and dispersion curve in a limited way. In addition, the investigation results show that the leakage zones inside the dam can be characterized by the anomalous low-velocity area of the inverted pseudo-two-dimensional (2D) S-wave velocity profile, validating the applicability of MASW in detecting the leakage zones of small earthen dams.