Electrical resistivity response due to variation in embankment shape and reservoir levels

Abstract

The safety of the center-core type of fill dam structure was assessed by examining the effects of the distortion of electrical response verified in terms of twodimensional (2D) apparent resistivity and its inverted sections from three-dimensional (3D) modeling for the embankment. The distortion effect is due to 2D interpretation of the 3D structure of the embankment. From the analysis, it was found that water level was correctly described by the resistivity section around the middle part rather than each side at the end of the embankment. This is due to the 3D terrain effect when the material of the embankment is assumed to be horizontally uniform. In addition, when the slope of the outer rock-fill section is set as uniform, the resistivity section is more similar for sharper center-core slopes. On the other hand, when the rock-fill slope is steep, the resistivity section shows the water level at a lower position than the real one, and the 3D distortion effect at the end of the embankment is enhanced.

A cost‐effective 3D electrical resistivity imaging approach applied to dike investigation

“…The first phase of the process consists in gathering all information on the investigated structure and the survey. Along with the accurate locations of the electrodes and a description of the acquisition protocol, two important categories of information are presented in Figure : information on “external“ media that has some influence on the geoelectrical measurements (Oh ; Fargier et al ) and available prior information on the investigated medium (including the substratum).…”

“…On one hand, their inner structure may exhibit strong longitudinal and transverse variability (e.g., presence of a clay core or repaired zones). On the other hand, embankment topography and high water‐level fluctuations adjacent to the dike have 3D effects on the resistivity measurements leading to image artefacts (Hennig, Weller, and Canh ; Sjödahl, Dahlin, and Zhou ; Oh ; Fargier et al ; Cho et al ). In order to account for the full 3D attributes of the problem, one would normally recommend the use of a complete 3D ERI procedure (e.g., Chambers et al ).…”

Reservoir assessment using non-invasive geophysical techniques

“…An examination of the literature discussing geophysical techniques applied to surveying flood embankments have shown the use of electrical resistivity tomography (ERT) to be common, due in part to the suitability of the construction materials (normally compacted, fine grained soils) and its sensitivity to changes in moisture as well as its ability to detect discontinuities in the material (Fargier et al 2014;Seokhoon 2012). ERT has been found as a good nondestructive technique, which gave the possibility of detecting internal erosion processes and to detect anomalous seepage (Sjödahl et al 2006(Sjödahl et al , 2010Cho and Yeom 2007;Lin et al 2014), at an early stage before the stability of the dam was compromised.…”