ERT Methodology for Identifying Humidity Content in Tailings Dams

The most frequent cause of failure on tailings dam is related to the action of water seepage and leakage through the tailings dam wall, resulting in instability and dam failure. In tailings failures reports around the world, one of the recommendations is to monitor periodically the conditions of non-saturation that were established at the dam design.

One of the methodologies of monitoring that has been increasingly used for the detection of internal erosion and infiltration, is through the observation of electrical resistivity, especially using the technique of electrical resistivity tomography (ERT). Even if this geophysical technique allows a ground characterization of resistivity, the step to convert this to humidity percentage is not simple, with certain difficulties also in the conversion to depth, and the definition or resolution that can achieve because of the interference of the tailings dam content, and the relationship between the resistivity and real humidity content that we want to detect.

We present the development of a methodology to obtain the real humidity percentage with ERT technique, testing the results using well depth humidity sensors in a tailings dam in Chile. The acquisition of ERT is currently an ongoing project during the well instrumentation campaign (with a depth of 5 to 60 meters) across the tailings dam (1100 meters length), and also taking well core samples to compare the level of saturation.