Tanguy Robert

University of Liège | ulg · Urban and Environmental Engineering

In the context of energy transition, new and renovated buildings often include heating and/or air conditioning energy-saving technologies based on sustainable energy sources, such as groundwater heat pumps with aquifer thermal energy storage. A new aquifer thermal energy storage system was designed and is under construction in the city of Liège, Be...

Since salt cannot always be used as a geophysical tracer (because it may pollute the aquifer with the mass that is necessary to induce a geophysical contrast), and since in many contaminated aquifer salts (e.g., chloride) already constitute the main contaminants, another geophysical tracer is needed to force a contrast in the subsurface that can be...

In the context of demand-side management and geothermal energy production, our proposal is to store thermal energy in shallow alluvial aquifers at shorter frequencies than classical seasonal aquifer thermal energy storage. We first conducted a one-week experiment in a shallow alluvial aquifer, which is characterized by a slow ambient groundwater fl...

In the last decades, aquifer thermal energy storage (ATES) has been proven to be a reliable renewable energy source. Yet, most of the ATES running systems are designed for seasonal or monthly storage and recovery applications. In the context of demand-side management, we have investigated the ability of such systems to perform short-term thermostat...

Recent developments in uncertainty quantification show that a full inversion of model parameters is not always necessary to forecast the range of uncertainty of a specific prediction in Earth sciences. Instead, Bayesian evidential learning (BEL) uses a set of prior models to derive a direct relationship between data and prediction. This recent tech...

In the context of aquifer thermal energy storage, we conducted a hydrogeophysical experiment emulating the functioning of a groundwater heat pump for heat storage into an aquifer. This experiment allowed the assessment of surface electrical resistivity tomography (ERT) ability to monitor the 3D development over time of the aquifer thermally affecte...

In this study, we tested the ability of geophysical methods to characterize a large technical landfill installed in a former sand quarry. The geophysical survey specifically aimed at delimitating the deposit site horizontal extension, at estimating its thickness and at characterizing the waste material composition (the moisture content in the prese...

In bioreactor landfills, the recirculation of water can accelerate biodegradation and increase gas production. The dedicated infrastructure aims at increasing wastewater content over a wide area, with a long-lasting effect. To assess the efficiency of horizontal drains in bioreactor landfills, we use electrical resistivity tomography (ERT) and dist...

Appropriate design of geophysical experiments combined with common hydrological measurements offer opportunities to use geophysical data as hard data in hydrological models, regarding their conceptualisation or their calibration. Two study sites located in Wallonia, Belgium, were investigated. In the first case (fractured limestone aquifer), stream...

[en] Applications of timelapse inversion of electrical resistivity tomography (ERT) allows\\monitoring variations in the subsurface that play a key role in a variety of contexts. The\\inversion of timelapse data provides successive images of the subsurface properties\\showing the medium evolution. Images quality is highly dependent on the data weig...

Dans les contextes de la flexibilité de la demande électrique (EDSM) et du stockage de chaleur en aquifère, le dimensionnement et le fonctionnement de systèmes géothermiques ouverts (ATES) sont étroitement liés à la géologie du site, hétérogène et complexe par définition. Afin de pouvoir développer des outils de modélisation prédictive fiable, nous...

The electrical resistivity tomography is a suitable method to estimate the water content of a waste material and detect changes in water content. Various ERT profiles, both static data and time-lapse, where acquired on a landfill during the Minerve project. In the literature, the relative change of resistivity (∆ρ/ρ) is generally computed. For sali...

The gravimetric water content of the waste material is a key parameter in waste biodegradation. Previous studies suggest a correlation between changes in water content and modification of electrical resistivity. This study, based on field work in Mont-Saint-Guibert landfill (Belgium), aimed, on one hand, at characterizing the relationship between g...

We have considered the problem of the choice of the minimum-gradient support (MGS) parameter in focused inversion for time-lapse (TL) electric resistivity tomography. Most existing approaches have relied either on an arbitrary choice of this parameter or one based on the prior information, such as the expected contrast in the TL image. We have deci...

In the context of energy demand side management (DSM), energy storage solutions are needed to stock energy during high production periods and recover energy during high demand periods. Among currently studied solutions, storing energy in the subsurface through heat pumps and/or exchangers (thermal energy storage) is relatively simple with low inves...

Low enthalpy geothermal systems exploited with ground source heat pumps or groundwater heat pumps present many advantages within the context of sustainable energy use. Designing, monitoring and controlling such systems requires the measurement of spatially distributed temperature fields and the knowledge of the parameters governing groundwater flow...

Several techniques are available to estimate the depth of investigation or to identify possible artifacts in dc resistivity surveys. Commonly, the depth of investigation (DOI) is mainly estimated by using an arbitrarily chosen cut-off value on a selected indicator (resolution, sensitivity or DOI index). Ranges of cut-off values are recommended in t...

We performed laboratory measurements on fully saturated sand samples in the context of deriving reliable temperature from time-lapse electrical resistivity tomography (ERT). The experiment consisted in monitoring an increase of temperature in sand samples with electrical resistivity measurements. We neglected the effect of surface conductivity sinc...

We performed laboratory measurements on fully saturated sand samples in the context of deriving reliable temperature from time-lapse electrical resistivity tomography (ERT). The experiment consisted in monitoring an increase of temperature in sand samples with electrical resistivity measurements. We neglected the effect of surface conductivity sinc...

The aim of this study is to monitor (bio) physical processes occurring in a landfill. The experiment consists in injecting leachate towards a drain in unsaturated and not yet digested waste to reactivate (or activate) waste biodegradation. The target is the first 15 meters of the studied landfill subsurface. The visualisation of the wet front arriv...

Several techniques are available to estimate the depth of investigation (DOI) or to identify possible artifacts in resistivity and IP surveys. Commonly, the DOI is mainly estimated using an arbitrarily chosen cut-off value on a selected resolution indicator (resolution, sensitivity or DOI index). Small changes in threshold values may induce strong...

In the context of landfill mining, we conducted electrical resistivity tomography (ERT), borehole electromagnetics (EM39), and magnetometry campaigns to characterise the subsurface of a waste deposit. The electrical resistivity structures in the landfill appear tabular with a first layer (12-15 m) characterised by higher resistivities (> 10 ohm.m;...

o date, few studies offer a quantitative comparison of the performance of image appraisal tools. Moreover, there is no commonly accepted methodology to handle them even though it is a crucial aspect for reliable interpretation of geophysical images. In this study, we compare quantitatively different image appraisal indicators to detect artefacts, e...

sses and quantification of parameters determining heat transport in porous media is therefore important. Geophysical methods may be useful in order to yield additional information with greater coverage than conventional wells. We report a heat transport study during a shallow heat injection and storage field test. Heated water (about 50°C) was inje...

The self-potential (SP) method relies on passive measurements of the ambient electrical potential at the ground surface or in boreholes. When the electrokinetic effect is the dominant contribution, the resulting signal is called the streaming potential and contains information about groundwater fluxes that can be useful for calibration of groundwat...

Many geophysical inverse problems are ill-posed leading to non-uniqueness of the solution. It is thus important to reduce the amount of mathematical solutions to more geologically plausible models by regularizing the inverse problem and incorporating all available prior information in the inversion process. We compare three different ways to go bey...

ERT and SP investigations were conducted in carbonate rocks of the Dinant Synclinorium (Walloon Region of Belgium) to find suitable locations for new water wells in zones with little hydrogeological data. Since boreholes information needed to be representative of the area, large fractured zones were searched for the drillings. Large ERT profiles (3...

The success of a tracer test highly depends on the number and the localisation of the sampling wells. When preferential solute transport paths are expected, one needs to set up carefully the tracer test to recover information such as the local groundwater flow direction and an estimate of the transport velocities. In this work, we used electrical r...

Electrical resistivity tomography (ERT) and self-potential (SP) investigations have been conducted in complex carboniferous limestones aquifers in Belgium (synclinorium structures). The aims of this study were (1) to detect and characterize fractured zones in hard rock aquifers, (2) to monitor groundwater flow/water content in these fractured or ka...