Use of MASW and Electrical Resistivity in Assessing a Small Earth Dam in Remote Area

The investigation aimed to identify any anomalies in the dam's structure, particularly internal seepage. The study employed a combination of geophysical and geotechnical techniques to gather data on the dam's soil properties and internal conditions. The ERT testing involved laying 28 electrodes on the crest of the dam, spaced at one-meter intervals, and analyzing the data using EarthImager 2D. The results showed a smooth model inversion, indicating a stable and reliable data fit. The 2D inverted model revealed three distinct soil layers at the crest of the dam, with resistivity values ranging from 10 ohm.m to 89 ohm.m, indicating clay-type soil. The presence of an anomaly at a depth of 4.5m was identified, suggesting possible seepage. The MASW technique involved laying 24 vertical geophones at one-meter spacing and analyzing the data using Geopsy and SeisImager software modules. The results showed a clear delay in the time of arrival followed by a ground roll, indicating a two-layer strata with the first layer having a shear velocity of approximately 70 m/s and the second layer having a higher shear velocity of 250 m/s. These values are consistent with a soft clay-type soil in earth dams for a similar depth. The DCP testing was conducted at 21m from the survey line, and the results showed the presence of three layers, with average values ranging from 2.5mm/blow to 1.5mm/blow. The corresponding ER values at the same location revealed the existence of three layers at approximately the same depth mentioned previously. The study's findings suggest that the earth dam in Laqlouq, Lebanon, consists of three distinct soil layers, with the presence of an anomaly at a depth of 4.5m indicating possible seepage. The results of the ERT, MASW, and DCP testing are consistent with each other, providing a comprehensive understanding of the dam's internal conditions. The study highlights the importance of using a combination of geophysical and geotechnical techniques to assess the health of earth dams and identify potential anomalies. The investigation of the earth dam in Laqlouq, Lebanon, has significant implications for the monitoring and inspection of earth dams in remote areas. The study's findings can be used to inform the development of more effective monitoring and inspection protocols, reducing the risk of internal seepage and failure. The use of ERT, MASW, and DCP testing can provide valuable insights into the internal conditions of earth dams, enabling more effective management and maintenance of these critical infrastructure structures. The study's results can also be applied to other earth dams in similar remote areas, providing a valuable resource for dam owners, operators, and regulatory agencies. The use of geophysical and geotechnical techniques can provide a cost-effective and non-invasive means of assessing the health of earth dams, reducing the need for expensive and invasive testing methods. The study's findings highlight the importance of using a combination of techniques to assess the internal conditions of earth dams, providing a more comprehensive understanding of these complex structures.