Estimation of Seepage Paths inside a Levee Using Multiple Parallel Resistivity Sections

Slope slide occurred at a point on the levee of a major river in Japan. To investigate the cause of the slide, the scanning electrical resistivity measurement was applied on four parallel survey lines along the banquettes of levee. As a result, two seepage paths are identified in the deep zone of the foundation and in the shallow zone of or above the foundation. The seepage path of shallow zone of the levee is identified with the highly permeable path, which is continuous from the river side to the land side. The location of seepage path is consistent with the location of the old road found in the old aerial photograph. The excavation of the area where the slope surface of levee was collapsed showed a stratum that is considered to be an old roadway masonry. This suggests that there was a sufficient supply of river water to cause the slope slide through the path with several hundred meters to cross the levee. The resistivity results also indicate that the two seepage paths, which are located near the old road and in the deep foundation, are independent of each other and cause different seepage phenomena.