Geotechnical and Geophysical Long-term Monitoring at a Levee of Red River in Vietnam

Abstract

The stability or safety of a levee during flooding depends on both the temporal development of the amplitude of the hydraulic loads in surface water and ground water and the change of soil parameters within the levee and subsoil. Therefore, a levee monitoring system should record the temporal development of the hydraulic loads of surface water and the resulting variations of water flow within the levee and subsoil. Long-term monitoring has been performed at a levee of Red River in Thai Binh province in Vietnam. The monitoring system consists of a permanent electrode array for resistivity imaging and geotechnical tools including tensiometers, frequency-domain reflectometry sensors and an observation well. The components were installed after a detailed inspection of the levee and foundation by drilling, sampling, and a geoelectrical survey. The levee monitoring system provided time series of the sensor data that were related to the variation of pore water pressure and water distribution. Additionally, the water level in the river and the precipitation rate were recorded. A two-dimensional transient finite element modeling of the seepage and groundwater flow was performed using the database of a single flood season. The resulting hydraulic model was used for a stability analysis. It could be shown that the stability calculations taking into account the transient development of the seepage line allows a more favorable safety factor in the stability analysis in comparison with the conventional steady state approach. According to our experience with the prototype of a levee monitoring system (LMS), the water level registration in the river, a tensiometer in the levee body and an observation well behind the levee should constitute the basic configuration of a LMS. The addition of more components improves the reliability of the system even in the case of failures of single sensors.

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

“…Many geophysical methods have been applied to earthen levee and dam condition assessments (e.g., Niederleithinger et al 2012), including DC resistivity techniques (e.g., Inazaki and Sakamoto 2005), low-frequency electromagnetic profiling (e.g., Fauchard and Mériaux 2007;Niederleithinger et al 2012), ground-penetrating radar (e.g., Carlsten, Johansson, and Wörman 1995;Antoine et al 2015), and seismic methods (e.g., Cardarelli, Cercato, and Di Filippo 2010;Cardarelli, Cercato, and De Donno 2014). DC electrical resistivity imaging (ERI) is widely applied to mapping the inner structure of dikes, as well as to detecting and monitoring seepage phenomena (e.g., Johansson and Dahlin 1996;Sjödahl et al 2008;Weller et al 2014). Furthermore, the efficiency of inte-terms in inverse problem formulations is a powerful means of introducing prior information that has been proved to be essential for retrieving reliable solutions (Ellis and Oldenburg 1994).…”

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

“…In our study, we use two-dimensional (2D) TL -ERT based on an embedded electrode installation to monitor the seasonal behaviour of soil moisture in an embankment levee along the Loire in France. TL -ERT based on permanently installed electrodes was introduced by Johansson and Dahlin (1996) on an embankment dam and has been more widely implemented since then (Sjödahl et al, 2008(Sjödahl et al, , 2009Kuras et al, 2009;Ogilvy et al, 2009;Chambers et al, 2014;Weller et al, 2014). The studied site is representative of old fluvial levees as it was first built in the 12 th century and has registered many floods and heightening works since then.…”

“…However, as previously mentioned, these measurements are punctual and probe installation can lead to soil disturbance. Thus, on many occasions, TL -ERT results are qualitatively correlated to water level variations and pluviometry (Panthulu et al, 2001;Lin et al, 2013Lin et al, , 2014Weller et al, 2014). In-situ temperature probes allows to build a simple temperature model for the levee that can be used to correct resistivity measurements (Chambers et al, 2014;Glendinning et al, 2015).…”

Separable Online System of Dike Monitoring Based on a Parallel-Serial Mode of Signal Measurement

“…Major modes of signal measurement in data acquisition include the serial ( [17], [18]), parallel ( [19], [20]) and distributed ( [21], [22]), etc. The serial mode has found more applications such as in river dikes ( [23], [24]), sea dikes ( [25], [26]) and road dikes ( [27], [28]). The distributed mode has found certain applications ( [14], [15]).…”