4D investigation of water infiltration in waste dumps using electrical resistivity (Elatsite mine, Bulgaria)

The objective was to investigate how water infiltrated into waste dumps at a mine site. The electrical resistivity method of field geophysics was applied to produce 4D imaging of progressive water infiltration into the waste dump. The goal is to test a method for investigating how rain water infiltrates unconsolidated materials in mine waste dumps. This is an important problem when evaluating the water balance in waste dumps and understanding the conditions for contamination of the water flowing through the waste materials. The trial was carried out in one of the two large dumps at Elatsite mine, which are composed of rocks with various fragment size and diverse mineral composition. The investigation was undertaken by discharging salt solution into the waste dump and taking geophysical measurements on a rectangular electrode grid at certain time intervals. The grid consisted of 64 electrodes forming 10×5 m cells and covering a 70×35 m area. As a result, it was possible to record how the infiltration and dispersion of the salt solution developed in space and time. In the last one of the seven surveys, 40 hours after the start of the trial, it was established that the salt solution reached a depth of approximately 40 m. The results could be used for predicting the interaction between water and waste material.