Fanny Descamps - Academia.edu (original) (raw)
Papers by Fanny Descamps
HAL (Le Centre pour la Communication Scientifique Directe), Nov 16, 2022
Cette recherche exploratoire applique pour la première fois la technique innovante du poinçonnage... more Cette recherche exploratoire applique pour la première fois la technique innovante du poinçonnage (Descamps et Tshibangu, 2004 ; Tshibangu et al., 2014) pour quantifier de façon peu invasive l'intensité de l'altération mécanique de la pierre monumentale en fonction de la profondeur d'altération. La recherche se concentre sur l'analyse de calcaires originaires de Wallonie (Belgique). L'échantillonnage est réalisé sur des fragments d'éléments architecturaux provenant de monuments récemment démantelés et datés du 17 e , 18 e , 19 e et 20 e siècle. La méthodologie d'analyse intègre une étude préalable scientifique et technique. Les profils de résistance obtenus à l'aide de la technique du poinçonnage sont analysés et discutés à la lumière de l'examen pétrographique des échantillons (LIBS) afin de considérer les variations de compositions chimique et micro-structurelle dans l'épaisseur des pierres de taille.
International audienceWallonia and Hauts-de-France face similar problems of ground movements rela... more International audienceWallonia and Hauts-de-France face similar problems of ground movements related to underground cavities. Those problems threaten people safety, land management and socio-economic attractiveness. Based on a cross-border dynamic, the RISSC Interreg project aims in improving the knowledge, prevention and management of risks related to underground cavities.La Wallonie et les Hauts-de-France connaissent des problèmes similaires de mouvements de terrains liés aux cavités souterraines, qui menacent la sécurité des personnes, l’aménagement du territoire et l’attractivité socio-économique. Basé sur une dynamique transfrontalière, le projet Interreg RISSC vise l’amélioration de la connaissance, de la prévention et de la gestion des risques liés aux terrains sous-cavés
Tous les corps émettent de l’énergie par rayonnement proportionnellement à leur température. Ce r... more Tous les corps émettent de l’énergie par rayonnement proportionnellement à leur température. Ce rayonnement est visible à haute température (métal en fusion, soleil, ...) mais se produit dans l’infrarouge lointain (autour de 10 μm) à température ambiante. La caméra de thermographie infrarouge mesure l’intensité du rayonnement thermique dans cette gamme de longueur d’onde grâce à la variation de résistance d’éléments sensibles en silicium. Cette intensité est ensuite convertie en température moyennant la connaissance de certains paramètres. Le plus important est l’émissivité de la surface qui doit être la plus élevée possible afin de minimiser les réflexions parasites du rayonnement des corps environnants sur la surface visée. Cette technique de mesure est largement utilisée dans le domaine du bâtiment en tant, par exemple, qu’outil de détection des ponts thermiques. Dans le cadre de projets menés dans le Service de Thermique et Combustion, elle est notamment utilisée pour mesurer l’...
<p>Monitoring of fluid movements in the crust is one of the most discussed topics in oil &a... more <p>Monitoring of fluid movements in the crust is one of the most discussed topics in oil & gas industry as well as in geothermal systems and CO<sub>2</sub> storage, but still remains a challenge. The seismic method is one of the most common ways to detect the fluid migration. However, the use of ultrasonic monitoring at the sample scale in laboratory experiments persists as the most effective way to highlight large scale observations in which the boundary conditions are not well constrained.</p><p>To unravel the fluid effect on P-wave and S-wave velocity, we performed mechanical experiments coupled with ultrasonic monitoring on Obourg chalk from Mons basin (Belgium). Water injection tests under critical loading, imbibition tests and evaporation tests provided a full spectrum of observations of fluid-induced wave alteration in term of propagation time and attenuation.</p><p>The analysis of these experimental results showed that significant velocity dispersion and attenuation developed through variations in water saturation, and that these processes are linked to the presence of patches of water and air in the pore space.</p><p>We used the White’s formulation to model the relaxation effects due to spherical pockets of air homogeneously distributed in a water-saturated medium. In this framework, the pressure induced by the passing wave, produces a fluid flow across the water-air boundary with consequent energy loss.</p><p>This model reproduces both qualitatively and quantitatively the experimental results observed on the water injection tests. Indeed, it is shown that the progressive water saturation or desaturation of this chalk, generates a shift of the critical frequency (from the undrained relaxed towards unrelaxed regimes) which at some point matches the resonance frequency of the piezoelectric transducers used in the experimental setup (0.5 MHz). This phenomenon allowed us to get a continuous recording of the relaxation processes induced by saturation variations.</p><p>The outcomes of this work can significantly improve the actual knowledge on coupled effects of waves and fluids which is a crucial aspect of fluid monitoring in the context of reservoir evaluation and production.</p>
Rock Mechanics and Rock Engineering, 2021
In the present work, we investigate the mechanical weakening and deformation induced by water on ... more In the present work, we investigate the mechanical weakening and deformation induced by water on a microporous carbonate rock, the Obourg Chalk from Mons Basin (Belgium), through conventional triaxial tests and injection tests. The injection tests were conducted by waterflooding critically loaded rock samples, initially in dry condition, in a way to minimize the variations in the effective pressures. Furthermore, the samples were instrumented with P-wave piezoelectric transducers to provide active ultrasonic monitoring while injecting. The results show a significant reduction in the mechanical strength of this chalk. Analysis of the mechanical tests and the associated deformation allows us to describe the mechanical behavior as a function of the confining pressure, which draws a brittle-ductile transition spanning from low to high confining pressure. The injection tests, moreover, revealed that the amount of water injected before triggering mechanical instability decreases exponentially with respect to the applied differential stress on the rock sample. The data, therefore, suggest that the failure might be controlled by a mechanical coupling between the water-invaded zone and the dry one. Since water-weakening plays an important role in several fields like oil industry, through secondary and tertiary recovery of hydrocarbons, Enhanced Geothermal Systems (EGS), as well as in the mechanical stability of underground cavities, the outcome of this work is of primary importance in mitigating any kind of problems related to these operations.
ISRM International Symposium - EUROCK 2020, Jun 14, 2020
Engineering in Chalk, 2018
Engineering in Chalk, 2018
Makala is a room-and-pillar coal mine situated in the Katanga Province (DR Congo), close to the c... more Makala is a room-and-pillar coal mine situated in the Katanga Province (DR Congo), close to the city of Kalemie (eastern part of the country). It exploits the so-named Lukuga Coal Basin which is composed by four coal seams numbered 1 to 4, but the economically mineable are 1 (about 2m thickness) and 2 (1 to 1.5m thickness). This coal basin shows some similarities with south-African deposits (Cahen 1961, in Carte Geologique du Zaire). From West the deposit plunges towards East with an average dip of 8°. Mining operations by room-and-pillar method started in 1914 on the northwestern part of the deposit, following the outcrops of coal seams. Currently only seam 1 is being mined out and the workings are being developed southwards to avoid the higher overburden towards East. Despite the increasing thickness of the overburden, the geometry of the method does not vary, and consists in rooms of 4m wide and pillars of 8x6m, leading to a recovery of about 60%. The main gallery lays from North...
Engineering in Chalk, 2018
Beyond the fundamental identification and characterisation of faults and joints in chalk, the fin... more Beyond the fundamental identification and characterisation of faults and joints in chalk, the fine description of fracture permeability, by means of analysing roughness, preferential flow channels and related tortuosity, is crucial in multiple applications such as underground stability studies, tunnelling, oil and gas production and related water injection, pollution control around contaminated zones, etc. Chalk exhibits a plastic behaviour beyond the elastic limit. The shearing, potentially extensive pattern of failure, leads to frequent and abundant fractures. As dynamic plate tectonics give form to various tectonic contexts, the resulting fractures can provide important flow channels within the porous media. Fracturing and alteration processes induce specific surfaces. Structures such as hackles, striations, or plumose patterns may emerge. Fault surfaces can display ridges or deep linear channels affecting the chalk matrix. The understanding of fractures surface geometry by observation and qualification is hence crucial, as it directly affects fluid transport. Textural modifications and surface properties (such as fracture plane roughness) derive directly from the fracturing mechanism and the flow process. As a result, the description and classification of rock fractures can be conducted via systemic cause-to-effect approach. In this study, we use a cross-motion table with CCD laser sensor to scan natural fractures in chalk as well as lab generated fractures. Working with samples collected in extensions of the North West European basin, the 3D characteristics of the surfaces are put in context with the tectonic background. Surface measurements will be compared to conventional techniques such as the JRC and other current methods (fractal and statistical fracture description), in view to consider an extension of fracture characterisation methods in three dimensions. Establishing a semi-automated method, this study will enable visualisation and classification of natural joints and faults, in view to improve fracture permeability depiction in fundamental studies or practical applications.
European Journal of Environmental and Civil Engineering, 2020
The Malogne Phosphatic chalk quarry was developed by the rooms and pillars mining method within a... more The Malogne Phosphatic chalk quarry was developed by the rooms and pillars mining method within an area of 67 ha. The site is partially flooded and located in close proximity to important infrastructure as railway, highway, and residential houses. During and after its exploitation several significant ground collapses were registered. The last one, with an area of 1.2 ha and 3 m amplitude occurred in 2015 nearby the railway line. To assess the behavior of the underground openings a combination of in situ structural measurements and laboratory mechanical characterisation in dry and saturated state of the main lithology type in the quarrywhite and phosphatic chalk, hard ground and calcarenites, are performed. The UCS of the chalk ranges from 4 to 10 MPa while its tensile strength is between 0.75 and 2.1 MPa. For the hardground, these values are over ten times higher. The results reveal significant influence of the water on the chalk properties by reduction of almost twice its strength. The data obtained was implemented in a conceptual geomechanical model, using the 2D FEM. Numerical results show a failure pattern that was confirmed from the in situ observations.
HAL (Le Centre pour la Communication Scientifique Directe), Nov 16, 2022
Cette recherche exploratoire applique pour la première fois la technique innovante du poinçonnage... more Cette recherche exploratoire applique pour la première fois la technique innovante du poinçonnage (Descamps et Tshibangu, 2004 ; Tshibangu et al., 2014) pour quantifier de façon peu invasive l'intensité de l'altération mécanique de la pierre monumentale en fonction de la profondeur d'altération. La recherche se concentre sur l'analyse de calcaires originaires de Wallonie (Belgique). L'échantillonnage est réalisé sur des fragments d'éléments architecturaux provenant de monuments récemment démantelés et datés du 17 e , 18 e , 19 e et 20 e siècle. La méthodologie d'analyse intègre une étude préalable scientifique et technique. Les profils de résistance obtenus à l'aide de la technique du poinçonnage sont analysés et discutés à la lumière de l'examen pétrographique des échantillons (LIBS) afin de considérer les variations de compositions chimique et micro-structurelle dans l'épaisseur des pierres de taille.
International audienceWallonia and Hauts-de-France face similar problems of ground movements rela... more International audienceWallonia and Hauts-de-France face similar problems of ground movements related to underground cavities. Those problems threaten people safety, land management and socio-economic attractiveness. Based on a cross-border dynamic, the RISSC Interreg project aims in improving the knowledge, prevention and management of risks related to underground cavities.La Wallonie et les Hauts-de-France connaissent des problèmes similaires de mouvements de terrains liés aux cavités souterraines, qui menacent la sécurité des personnes, l’aménagement du territoire et l’attractivité socio-économique. Basé sur une dynamique transfrontalière, le projet Interreg RISSC vise l’amélioration de la connaissance, de la prévention et de la gestion des risques liés aux terrains sous-cavés
Tous les corps émettent de l’énergie par rayonnement proportionnellement à leur température. Ce r... more Tous les corps émettent de l’énergie par rayonnement proportionnellement à leur température. Ce rayonnement est visible à haute température (métal en fusion, soleil, ...) mais se produit dans l’infrarouge lointain (autour de 10 μm) à température ambiante. La caméra de thermographie infrarouge mesure l’intensité du rayonnement thermique dans cette gamme de longueur d’onde grâce à la variation de résistance d’éléments sensibles en silicium. Cette intensité est ensuite convertie en température moyennant la connaissance de certains paramètres. Le plus important est l’émissivité de la surface qui doit être la plus élevée possible afin de minimiser les réflexions parasites du rayonnement des corps environnants sur la surface visée. Cette technique de mesure est largement utilisée dans le domaine du bâtiment en tant, par exemple, qu’outil de détection des ponts thermiques. Dans le cadre de projets menés dans le Service de Thermique et Combustion, elle est notamment utilisée pour mesurer l’...
<p>Monitoring of fluid movements in the crust is one of the most discussed topics in oil &a... more <p>Monitoring of fluid movements in the crust is one of the most discussed topics in oil & gas industry as well as in geothermal systems and CO<sub>2</sub> storage, but still remains a challenge. The seismic method is one of the most common ways to detect the fluid migration. However, the use of ultrasonic monitoring at the sample scale in laboratory experiments persists as the most effective way to highlight large scale observations in which the boundary conditions are not well constrained.</p><p>To unravel the fluid effect on P-wave and S-wave velocity, we performed mechanical experiments coupled with ultrasonic monitoring on Obourg chalk from Mons basin (Belgium). Water injection tests under critical loading, imbibition tests and evaporation tests provided a full spectrum of observations of fluid-induced wave alteration in term of propagation time and attenuation.</p><p>The analysis of these experimental results showed that significant velocity dispersion and attenuation developed through variations in water saturation, and that these processes are linked to the presence of patches of water and air in the pore space.</p><p>We used the White’s formulation to model the relaxation effects due to spherical pockets of air homogeneously distributed in a water-saturated medium. In this framework, the pressure induced by the passing wave, produces a fluid flow across the water-air boundary with consequent energy loss.</p><p>This model reproduces both qualitatively and quantitatively the experimental results observed on the water injection tests. Indeed, it is shown that the progressive water saturation or desaturation of this chalk, generates a shift of the critical frequency (from the undrained relaxed towards unrelaxed regimes) which at some point matches the resonance frequency of the piezoelectric transducers used in the experimental setup (0.5 MHz). This phenomenon allowed us to get a continuous recording of the relaxation processes induced by saturation variations.</p><p>The outcomes of this work can significantly improve the actual knowledge on coupled effects of waves and fluids which is a crucial aspect of fluid monitoring in the context of reservoir evaluation and production.</p>
Rock Mechanics and Rock Engineering, 2021
In the present work, we investigate the mechanical weakening and deformation induced by water on ... more In the present work, we investigate the mechanical weakening and deformation induced by water on a microporous carbonate rock, the Obourg Chalk from Mons Basin (Belgium), through conventional triaxial tests and injection tests. The injection tests were conducted by waterflooding critically loaded rock samples, initially in dry condition, in a way to minimize the variations in the effective pressures. Furthermore, the samples were instrumented with P-wave piezoelectric transducers to provide active ultrasonic monitoring while injecting. The results show a significant reduction in the mechanical strength of this chalk. Analysis of the mechanical tests and the associated deformation allows us to describe the mechanical behavior as a function of the confining pressure, which draws a brittle-ductile transition spanning from low to high confining pressure. The injection tests, moreover, revealed that the amount of water injected before triggering mechanical instability decreases exponentially with respect to the applied differential stress on the rock sample. The data, therefore, suggest that the failure might be controlled by a mechanical coupling between the water-invaded zone and the dry one. Since water-weakening plays an important role in several fields like oil industry, through secondary and tertiary recovery of hydrocarbons, Enhanced Geothermal Systems (EGS), as well as in the mechanical stability of underground cavities, the outcome of this work is of primary importance in mitigating any kind of problems related to these operations.
ISRM International Symposium - EUROCK 2020, Jun 14, 2020
Engineering in Chalk, 2018
Engineering in Chalk, 2018
Makala is a room-and-pillar coal mine situated in the Katanga Province (DR Congo), close to the c... more Makala is a room-and-pillar coal mine situated in the Katanga Province (DR Congo), close to the city of Kalemie (eastern part of the country). It exploits the so-named Lukuga Coal Basin which is composed by four coal seams numbered 1 to 4, but the economically mineable are 1 (about 2m thickness) and 2 (1 to 1.5m thickness). This coal basin shows some similarities with south-African deposits (Cahen 1961, in Carte Geologique du Zaire). From West the deposit plunges towards East with an average dip of 8°. Mining operations by room-and-pillar method started in 1914 on the northwestern part of the deposit, following the outcrops of coal seams. Currently only seam 1 is being mined out and the workings are being developed southwards to avoid the higher overburden towards East. Despite the increasing thickness of the overburden, the geometry of the method does not vary, and consists in rooms of 4m wide and pillars of 8x6m, leading to a recovery of about 60%. The main gallery lays from North...
Engineering in Chalk, 2018
Beyond the fundamental identification and characterisation of faults and joints in chalk, the fin... more Beyond the fundamental identification and characterisation of faults and joints in chalk, the fine description of fracture permeability, by means of analysing roughness, preferential flow channels and related tortuosity, is crucial in multiple applications such as underground stability studies, tunnelling, oil and gas production and related water injection, pollution control around contaminated zones, etc. Chalk exhibits a plastic behaviour beyond the elastic limit. The shearing, potentially extensive pattern of failure, leads to frequent and abundant fractures. As dynamic plate tectonics give form to various tectonic contexts, the resulting fractures can provide important flow channels within the porous media. Fracturing and alteration processes induce specific surfaces. Structures such as hackles, striations, or plumose patterns may emerge. Fault surfaces can display ridges or deep linear channels affecting the chalk matrix. The understanding of fractures surface geometry by observation and qualification is hence crucial, as it directly affects fluid transport. Textural modifications and surface properties (such as fracture plane roughness) derive directly from the fracturing mechanism and the flow process. As a result, the description and classification of rock fractures can be conducted via systemic cause-to-effect approach. In this study, we use a cross-motion table with CCD laser sensor to scan natural fractures in chalk as well as lab generated fractures. Working with samples collected in extensions of the North West European basin, the 3D characteristics of the surfaces are put in context with the tectonic background. Surface measurements will be compared to conventional techniques such as the JRC and other current methods (fractal and statistical fracture description), in view to consider an extension of fracture characterisation methods in three dimensions. Establishing a semi-automated method, this study will enable visualisation and classification of natural joints and faults, in view to improve fracture permeability depiction in fundamental studies or practical applications.
European Journal of Environmental and Civil Engineering, 2020
The Malogne Phosphatic chalk quarry was developed by the rooms and pillars mining method within a... more The Malogne Phosphatic chalk quarry was developed by the rooms and pillars mining method within an area of 67 ha. The site is partially flooded and located in close proximity to important infrastructure as railway, highway, and residential houses. During and after its exploitation several significant ground collapses were registered. The last one, with an area of 1.2 ha and 3 m amplitude occurred in 2015 nearby the railway line. To assess the behavior of the underground openings a combination of in situ structural measurements and laboratory mechanical characterisation in dry and saturated state of the main lithology type in the quarrywhite and phosphatic chalk, hard ground and calcarenites, are performed. The UCS of the chalk ranges from 4 to 10 MPa while its tensile strength is between 0.75 and 2.1 MPa. For the hardground, these values are over ten times higher. The results reveal significant influence of the water on the chalk properties by reduction of almost twice its strength. The data obtained was implemented in a conceptual geomechanical model, using the 2D FEM. Numerical results show a failure pattern that was confirmed from the in situ observations.