Safety assessment and treatment techniques of an operated dam with a leakage problem: case study of Hisarardi embankment dam

An uncontrolled leakage and piping in embankment dams may cause breaching and slope slides. Clarification of the cause of an embankment leakage is also crucial to determine the effective and economical treatment method. However, identification of the source of a leakage in embankment dams is a difficult task since site investigations and computation methods may vary significantly depending on the site geology, topography, and embankment material properties. This paper presents an exemplary distinctive study and treatment methods of a leakage problem of an embankment dam located on seismically active region wherein the site is under the risk of 89 active faults capable of producing magnitudes over 6.0. Calculated slope failure probability of the dam due to the leakage-related saturation of the downstream zone is significantly high as 0.89. Numerical seepage analyses were also performed to determine whether the leakage was related to a piping incident or a filter deficiency. Particularly, bottom outlet valve on/off operations and satellite image approaches and their interpretations enabled the finding that the leakage on the dam occurred due to the bottom outlet deterioration. The deterioration of the bottom outlet resulted in high water uplift pressure into and saturation of the downstream sandyfill beyond the chimney filter. Finally, the study discusses two different treatment techniques: (1) the application of a geomembrane on the upstream face that did not prevent the leakage, and (2) driving an HDPE pipe into the existing steel bottom outlet pipe, a rapid, economical, and effective solution that prevented the leakage. This study provides different evaluations of the reason of the leakage problem and effective treatment process of a bottom outlet which can be useful for other embankment dams having such leakage problems.