Équipements

Autonomous Sensors for Measuring Continuously the Moisture and Salinity of a Porous Medium

Papers - Publications scientifiques

The article describes a new field sensor to monitor continuously in situ moisture and salinity of a porous medium via measurements of its dielectric permittivity, conductivity and temperature. It intends to overcome difficulties and biases encountered with sensors based on the same sensitivity principle. Permittivity and conductivity are determined simultaneously by a self-balanced bridge, which measures directly the admittance of […]

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pyGrav, a Python-based program for handling and processing relative gravity data

Papers - Publications scientifiques

pyGrav is a Python-based open-source software dedicated to the complete processing of relative-gravity data. It is particularly suited for time-lapse gravity surveys where high precision is sought. Its purpose is to bind together single-task processing codes in a user friendly interface for handy and fast treatment of raw gravity data from many stations of a network. The intuitive object-based implementation […]

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Evaluation and localization of an artificial drainage network by 3D time-lapse electrical resistivity tomography

Papers - Publications scientifiques

In France, 10 % of total arable land is equipped with subsurface drainage systems, to control winter and spring waterlogging due to a temporary perched water table. Most of these systems were installed in the 1980s and have aged since then and may now need maintenance. Sometimes, the location of the systems is known, but the standard situation in France […]

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Small-Scale Seismic Monitoring of Varying Water Levels in Granular Media

Papers - Publications scientifiques

Physical properties of soils in the vadose zone, and especially their water content, are characterized by strong spatial and temporal variations mostly driven by weather and anthropogenic activities. To understand this variability and help water resource management, seismic methods have been recently suggested as a complement to electrical and electromagnetic techniques. The simultaneous in situ estimation of pressure (P) and […]

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2D characterization of near-surface VP/VS: surface-wave dispersion inversion versus refraction tomography

Papers - Publications scientifiques

The joint study of pressure (P-) and shear (S-) wave velocities (VP and VS), as well as their ratio (VP/VS), has been used for many years at large scales but remains marginal in near-surface applications. For these applications, VP and VS are generally retrieved with seismic refraction tomography combining P and SH (shear-horizontal) waves, thus requiring two separate acquisitions. Surface-wave […]

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Integrated Workflow for Surface-wave Dispersion Inversion and Profiling

Papers - Publications scientifiques

While surface-wave prospecting methods are classically applied for the one-dimensional (1D) estimation of shear (S-) wave velocities (Vs), two-dimensional (2D) profiling still requires implementing specific processing and inversion tools that are not yet widely available in the community. We present here a free and open-source tool performing surface-wave inversion and profiling (SWIP) in order to retrieve 2D lateral variations of […]

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Field Continuous Measurement of Dissolved Gases with a CF-MIMS: Applications to the Physics and Biogeochemistry of Groundwater Flow

In the perspective of a temporal and spatial exploration of aquatic environments (surface and groundwater), we developed a technique for field continuous measurements of dissolved gases with a precision better than 1% for N2, O2, CO2, He, Ar, 2% for Kr, 8% for Xe, and 3% for CH4, N2O and Ne. With a large resolution (from 1 × 10–9 to […]

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Presentation of a Complex Permittivity-Meter with Applications for Sensing the Moisture and Salinity of a Porous Media

Papers - Publications scientifiques

This paper describes a sensor dedicated to measuring the vertical profile of the complex permittivity and the temperature of any medium in which sensor electrodes are inserted. Potential applications are the estimate of the humidity and salinity in a porous medium, such as a soil. It consists of vertically-stacked capacitors along two conductive parallel cylinders of 5 cm in diameter and at a 10-cm […]

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Hydrogeophysical characterization of transport processes in fractured rock by combining push-pull and single-hole ground penetrating radar experiments

The in situ characterization of transport processes in fractured media is particularly challenging due to the considerable spatial uncertainty on tracer pathways and dominant controlling processes, such as dispersion, channeling, trapping, matrix diffusion, ambient and density driven flows. We attempted to reduce this uncertainty by coupling push-pull tracer experiments with single-hole ground penetrating radar (GPR) time-lapse imaging. The experiments involved different injection fractures, chaser […]

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Active-Distributed Temperature Sensing to continuously quantify vertical flow in boreholes

We show how a distributed borehole flowmeter can be created from armored Fiber Optic cables with the Active-Distributed Temperature Sensing (A-DTS) method. The principle is that in a flowing fluid, the difference in temperature between a heated and unheated cable is a function of the fluid velocity. We outline the physical basis of the methodology and report on the deployment […]

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