). Le but de ce projet est de reproduire les feux identifiés dans la grotte ornée de Chauvet-Pont... more ). Le but de ce projet est de reproduire les feux identifiés dans la grotte ornée de Chauvet-Pont-d'Arc (Paléolithique supérieur, 29-33 000 BP) et de comparer leurs effets avec ce qui a été observé dans la cavité. Des conditions de foyer similaires à celles mises en oeuvre au Paléolithique ont ainsi été recréées, en milieu souterrain, dans une carrière de roche calcaire du Rupélien à Lugasson (33) et dans laquelle une paroi rocheuse a été soumise à un feu expérimental durant une demi-journée. Nous présentons dans ce papier les principales observations expérimentales ainsi qu'une étude numérique dont le but est d'estimer les effets thermomécaniques potentiels du feu sur la paroi.
Near Surface Geoscience 2014 - 20th European Meeting of Environmental and Engineering Geophysics, 2014
The decorated cave in Dordogne needs more attention while being studied and conserved. Geophysica... more The decorated cave in Dordogne needs more attention while being studied and conserved. Geophysical methods enable in a non-invasive way to detect the underground environment of the decorated cave. Associated with the analysis of the effective rainfall (groundwater recharge) in this site and the flow in the cave, the Electrical Resistivity Tomography monitoring using pole-dipole and gradient arrays has identified a zone which probably stores water in relation with the cave. There is a high electrical contrast between the surrounding limestone and the probably recharge zone. Then, with a multivariate analysis through the resistivity values allows us to characterize the model blocks showing a specific behavior over time, especially the blocks the lowest electrical resistivity. The main result of this study is that these blocks are assumed to be probably a part of the recharge area; systematic electrical survey after raining event could be used to predict the beginning of the underground flow in order to give advice for preserving the Lascaux Cave.
Le contrNe non destructif des ouvrages de g~nie civil en b4ton et bfton armd repr~sente un int4rf... more Le contrNe non destructif des ouvrages de g~nie civil en b4ton et bfton armd repr~sente un int4rfit majeur pour la gestion du patrimoine bfiti. Les m&hodes g4ophysiques, rdguli6rement employees en g4ologie, restent encore mal maltris4es dans ce cadre.
In this paper we analyze the onsite characterization of a geosynthetic clay liner (GCL) that serv... more In this paper we analyze the onsite characterization of a geosynthetic clay liner (GCL) that serves to ensure the impermeability of a landfill cap by DC electrical methods. The imaging of the GCL geoelectrical properties is a challenging problem because it is a very thin (between 4 and 7 mm thick) and resistive layer (from 100,000 to 2,000,000 Ω·m) depending on meteorological conditions and aging. We compare results obtained using electrical resistivity tomography (ERT) using two different kinds of arrays (dipole-dipole DD and Wenner-Schlumberger) on an experimental site with engineered defects. To confirm these results and to find the real onsite GCL resistivity we have performed sampling of the posterior distribution of this parameter using vertical electrical sounding (VES) inversions. Different VES methods were extracted from ERT with DD array and converted into a Schlumberger array. As a main conclusion the dipole-dipole array provides a better resistivity resolution of the defects than the Wenner-Schlumberger array. On ERT images, the defect detection seems to be impossible if the GCL has very high resistivity, as it happened when it was put in place. Taking into account the equivalence rules, the inversions are in both cases (ERT and VES) compatible. The GCL resistivity estimated from PSO (particle swarm optimization) varies from 3.0 10 5 to 1.10 6 Ω·m depending on saturation conditions during the twenty first months of its placing. Then, the resistivity dropped to 4.10 4 -9.10 4 Ω·m, indicating a probable chemical damage of the GCL due to aging. Finally the fact that the VES inversions are solved via PSO sampling allows for the detection of a very thin and resistive layer and opens the possibility of performing micro VES surveys along the landfill to detect possible GCL defects.
Non-destructive evaluation appears more and more important in the civil engineering economic stak... more Non-destructive evaluation appears more and more important in the civil engineering economic stakes. In this context electrical resistivity measurements get sensitivity to parameters allowing to assess concrete structures conditions. This article analyses the ability of the resistivity measurement to study cracks in concrete. Its ability to detect and to locate cracks and spalling is shown with on site measurements on a damaged slab. Then specific studies on such disorders allow to distinguish the influence of their characteristics.
). Le but de ce projet est de reproduire les feux identifiés dans la grotte ornée de Chauvet-Pont... more ). Le but de ce projet est de reproduire les feux identifiés dans la grotte ornée de Chauvet-Pont-d'Arc (Paléolithique supérieur, 29-33 000 BP) et de comparer leurs effets avec ce qui a été observé dans la cavité. Des conditions de foyer similaires à celles mises en oeuvre au Paléolithique ont ainsi été recréées, en milieu souterrain, dans une carrière de roche calcaire du Rupélien à Lugasson (33) et dans laquelle une paroi rocheuse a été soumise à un feu expérimental durant une demi-journée. Nous présentons dans ce papier les principales observations expérimentales ainsi qu'une étude numérique dont le but est d'estimer les effets thermomécaniques potentiels du feu sur la paroi.
Near Surface Geoscience 2014 - 20th European Meeting of Environmental and Engineering Geophysics, 2014
The decorated cave in Dordogne needs more attention while being studied and conserved. Geophysica... more The decorated cave in Dordogne needs more attention while being studied and conserved. Geophysical methods enable in a non-invasive way to detect the underground environment of the decorated cave. Associated with the analysis of the effective rainfall (groundwater recharge) in this site and the flow in the cave, the Electrical Resistivity Tomography monitoring using pole-dipole and gradient arrays has identified a zone which probably stores water in relation with the cave. There is a high electrical contrast between the surrounding limestone and the probably recharge zone. Then, with a multivariate analysis through the resistivity values allows us to characterize the model blocks showing a specific behavior over time, especially the blocks the lowest electrical resistivity. The main result of this study is that these blocks are assumed to be probably a part of the recharge area; systematic electrical survey after raining event could be used to predict the beginning of the underground flow in order to give advice for preserving the Lascaux Cave.
Le contrNe non destructif des ouvrages de g~nie civil en b4ton et bfton armd repr~sente un int4rf... more Le contrNe non destructif des ouvrages de g~nie civil en b4ton et bfton armd repr~sente un int4rfit majeur pour la gestion du patrimoine bfiti. Les m&hodes g4ophysiques, rdguli6rement employees en g4ologie, restent encore mal maltris4es dans ce cadre.
In this paper we analyze the onsite characterization of a geosynthetic clay liner (GCL) that serv... more In this paper we analyze the onsite characterization of a geosynthetic clay liner (GCL) that serves to ensure the impermeability of a landfill cap by DC electrical methods. The imaging of the GCL geoelectrical properties is a challenging problem because it is a very thin (between 4 and 7 mm thick) and resistive layer (from 100,000 to 2,000,000 Ω·m) depending on meteorological conditions and aging. We compare results obtained using electrical resistivity tomography (ERT) using two different kinds of arrays (dipole-dipole DD and Wenner-Schlumberger) on an experimental site with engineered defects. To confirm these results and to find the real onsite GCL resistivity we have performed sampling of the posterior distribution of this parameter using vertical electrical sounding (VES) inversions. Different VES methods were extracted from ERT with DD array and converted into a Schlumberger array. As a main conclusion the dipole-dipole array provides a better resistivity resolution of the defects than the Wenner-Schlumberger array. On ERT images, the defect detection seems to be impossible if the GCL has very high resistivity, as it happened when it was put in place. Taking into account the equivalence rules, the inversions are in both cases (ERT and VES) compatible. The GCL resistivity estimated from PSO (particle swarm optimization) varies from 3.0 10 5 to 1.10 6 Ω·m depending on saturation conditions during the twenty first months of its placing. Then, the resistivity dropped to 4.10 4 -9.10 4 Ω·m, indicating a probable chemical damage of the GCL due to aging. Finally the fact that the VES inversions are solved via PSO sampling allows for the detection of a very thin and resistive layer and opens the possibility of performing micro VES surveys along the landfill to detect possible GCL defects.
Non-destructive evaluation appears more and more important in the civil engineering economic stak... more Non-destructive evaluation appears more and more important in the civil engineering economic stakes. In this context electrical resistivity measurements get sensitivity to parameters allowing to assess concrete structures conditions. This article analyses the ability of the resistivity measurement to study cracks in concrete. Its ability to detect and to locate cracks and spalling is shown with on site measurements on a damaged slab. Then specific studies on such disorders allow to distinguish the influence of their characteristics.
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Papers by C. Sirieix