Monitoring of internal erosion processes by time-lapse electrical resistivity tomography

Internal erosion phenomena are a major threat to all earthen structures, such as river levees and dams. Studying these phenomena has been limited because they occur concealed inside the material, which makes them difficult to observe and monitor. Non-destructive geophysical monitoring techniques are powerful tools that can provide insight into the processes involved. For this reason, a test rig has been specifically designed to conduct three-dimensional electrical resistivity tomography of soil specimens undergoing internal erosion due to seepage. Two suffusion tests were conducted where the erosion evolution has been monitored. The time-series of eroded mass weight were then used to correlate the changes in three-dimensional resistivity distribution to the porosity change in media by means of Archie's law. The results from the first suffusion test were used to calibrate Archie's model parameters. It was found that the resistivity variations were able to predict changes in the porous matrix structure. The data obtained from the second test were used to validate the model parameters and confirmed that the time-lapse three-dimensional inverted resistivity images were able to successfully quantify the global erosion rate.