Multi‐electrode measurements at Thai Binh dikes (Vietnam)

Abstract

The province of Thai Binh is located in the delta of the Red River in Vietnam where an extensive system of river and sea dikes protects the population and infrastructure from flooding in the rainy season. The integrity of the river dikes is affected by a diversity of problems. Importantly, various termite species dig their nests in the dikes causing water leakage. Leakage can also occur near sluices and passages. Geoelectrical multi‐electrode profiling has been applied to locate defects in the dikes. Surveys carried out on several dikes demonstrated that a combined half‐Wenner configuration yields high‐resolution images in which termite nests are indicated by resistive anomalies. Petrophysical investigations of soil samples and density logs yield additional information on the dike material. Elsewhere, imaging surveys confirmed the subsurface extent of a buried sluice structure in the dike body.

An approach to construct the weathering profile in a hilly granitic terrain based on electrical imaging

“…DC2DSIRT is based on a finite difference forward modeling and a simultaneous iterative reconstruction technique for inversion. The program has been successfully applied to analyze resistivity data for hydrogeological, engineering, and archaeological problems (Olayinka and Weller, 1997;Schleifer et al, 2002;Weller et al, 2006). Olayinka and Weller (1997) used the program to show that resulting resistivity model including the surface of the crystalline basement severely depends on the choice of the starting model.…”

Object orientated focussing of geoelectrical multielectrode measurements

“…Several species of termites build their nests into the dike body. Thus the stability of dikes is affected (Weller et al, 2006). Regarding the data of numerous excavations, the average dimension and depth of termite nests could be defined.…”

“…According to earlier investigations (Weller et al, 2006) the mean size of termite nests is 2.0 × 2.0 m 2 and the depth ranges from 0 to 2.0 m. Using these data a filter providing high sensitivity in this area was constructed (Fig. 11).…”

2D-ERT monitoring of soil moisture seasonal behaviour in a river levee: A case study

“…Among geophysical imaging methods, electrical resistivity tomography (ERT) is a wellestablished method that is widely applied to embankment levee investigation and seepage detection (e.g. Johansson and Dahlin 1996;Sjödahl et al, 2005Sjödahl et al, , 2010Weller et al, 2006;Cho and Yeom, 2007;Chinedu and Ogah, 2013;Lin et al, 2014;Loperte et al, 2016). Its sensitivity to soil moisture makes it an appropriate technique for monitoring purposes in the form of timelapse ERT (TL -ERT) surveys, that allows locating zones with abnormal seepage variations in time (Sjodahl et al, 2008), which is of upmost importance.…”