Characterization of a leaky earth dam using integrated geophysical surveys

Early earth dams were mainly constructed using a soil core wall, which is susceptible to a variety of potential risks such as inhomogeneity, poor compactness, and leakage due to multiple fillings and biological damage. To ensure safe operation of the dam, cost-effective geophysical non-destructive testing techniques should be considered during routine maintenance. This paper presents a case study of an earth dam designed for water storage and flood control that experienced a leak problem. To provide a basis for future leakage control, we carried out 2D integrated geophysical surveys utilizing Electric Resistivity Tomography (ERT), Ground Penetrating Radar (GPR), and Surface Wave (SW) methods along the dam axis. In conjunction with the fast attenuation characteristic of GPR signals, the low resistivity anomalies recovered by the ERT provide evidence to reveal the leakage area within the dam structure. Moreover, the shear wave velocity variation retrieved by the SW method helps to determine the distribution of bedrock and soil layers. By integrating the results mentioned above, the interpretation outcome yields a comprehensive understanding of the internal condition of the earth dam. The successful investigation of the dam structure and the mapping of the leakage area demonstrate the effectiveness of integrated geophysical surveys in characterizing earth dams. It also suggests that it is essential to consider the difference between various geophysical results and the underlying reason when integrating them to characterize leaky earth dams.