Evaluation of wet front under foundation at “El Chocón dam” using electrical tomography

Abstract

El Chocón dam is located on Limay River in the province of Neuquén (Argentina) and is one of the most important in the country and in Latin America due its reservoir capacity. Currently, the dam is at full operation stage, while its structural health is monitored through a significant number of instruments installed in the dam body and its foundation. In the sector of the closure of the dam on its left margin, the measurements of some piezometers that monitor the deep rock foundation, showed some changes that gave rise to the hypothesis of the advance of wet front, despite fact that the work has practically 50 years from commissioning. To confirm or rule out this hypothesis, research work was started using the 2D electrical tomography method. The methodology was selected based on the good correlation that exists between the electrical resistivity and the volumetric content of water in a rock formation. Tomographic image obtained made it possible to determine different sectors in which wet front is detected and to define its extension, also evidencing a good correlation with what was recorded in the rock auscultation instruments, confirming the slow advance of wet front to downstream.

Keywords

• dam monitoring
• electrical tomography
• rock resistivity