Spectral analysis of surface waves for the characterization of the EDZ in circular galleries

Lors du creusement de galeries profondes ou de tunnels, les propriétés hydromécaniques de la roche encaissante autour de l'ouvrage sont altérées sur une certaine distance qui dépend de la nature de la roche et du type d'excavation. Une telle zone est appelée Excavation Damaged Zone (EDZ). Cette altération de l'encaissant se caractérise par une densification de la fracturation intrinsèque de la roche. La connaissance des caractéristiques mécaniques de l'EDZ ainsi que son extension est actuellement un axe majeur de recherche notamment pour la conception de centres de stockage souterrains des déchets nucléaires. En effet, l'EDZ, par son réseau de fractures, est considéré comme un chemin potentiel pour les radionucléides et donc comme un facteur de possible contamination du milieu. Les méthodes géophysiques initialement utilisées à des échelles kilométriques pour analyser les événements géologiques, sont dorénavant transposées à des échelles métriques voire centimétriques et appliquées en génie civil ou dans tout autre domaine de l'ingénierie. L'intérêt de telles méthodes est leur caractère non destructif qui les rend faciles d'utilisation et généralement moins coûteuses que d'autres méthodes destructives. Elles permettent aussi un suivi dans le temps de l'évolution des propriétés des matériaux auscultés. La MASW (Multiple Acquisition of Surface Wave) est une méthode géophysique utilisant le principe de dispersion des ondes de surface (Park et al, 1999). Cette méthode a été transposée dans ce contexte afin d'obtenir un profil 1D des vitesses des ondes de cisaillement (S) autour d'un ouvrage souterrain et ainsi de déterminer l'extension et les caractéristiques en terme de vitesse des ondes S de l'EDZ. L'intérêt de cette méthode est sa facilité de mise en oeuvre et la possibilité de l'utiliser sans restriction majeure

Feedback on methods of characterization of damage around underground structures in argillites by analyzing wave propagation

The Callovo-Oxfordian claystones were chosen for their low permeability. This feature marked by the clay content of the rock is inevitably accompanied by a low tensile strength. This generates the development of an excavation damaged zone. Seismic elastic wave propagation analysis methods are potentially valuable for the characterization of the damaged zone. These methods are more or less adapted to clay environment mainly due to the strong wave attenuation. The easiest seismic method to implement is probably the seismic refraction. It is used from the surface of the wall. It involves analyzing the waves refracted at the interface between the fractured zone and the bedrock. Sato et al. (2003) showed with this method the influence of excavation mode on the extension of the damaged zone in the underground laboratory in Japan Tono (sedimentary clay rock). Similarly, Lagarde et al. (2006) used the method in the Callovo-Oxfordian claystone. The application of seismic refraction in this context is at the limit of resolution because it assumes a multilayer tabular model without velocity reverse and the error on the arrival time measured is very close to time variations due to the damaged zone. The analysis of the surface waves is based on the dispersive property of these waves. They have the particularity to propagate at different depths depending on their frequency. The objective is therefore to measure the dispersion curve of the wave model and find the velocity profile that best matches. This method called MASW (Multi-Channel Acquisition of Surface Waves) is typically used to find the velocity profile of a tabular field where the inversion is simplified. As part of the thesis of Lagarde (2007), the MASW method was extended to the concave geometry of deep underground excavations to characterize the velocity profile in the damaged zone. It makes it possible to reveal any velocity profile including those with one or more velocity reverse. This method was used at the Meuse Haute Marne URL to characterize the damaged zone at the bottom of a drift. Seismic methods can also be implemented in borehole, for example ultrasonic logs. They are well suited to the scale of the damaged zone and numerous surveys in deep underground excavations. In the Meuse Haute Marne URL, this method has been used on numerous occasions (Schuster et al, 2001) during the different phases of the excavation of shafts and galleries. These velocity measurements are used to describe both the evolution of the gradient of damage / deconfinement from gallery wall and isolated fractures at greater depth. Acoustic emissions (AE) occur during initiation and expansion of cracks. Quantifying and locating those AE can bring information in determining the initiation and expansion of the damaged zone. Monitoring these AE has been successfully applied around structures in very resistant rock under high stresses such as granite host rocks of the Lac du Bonnet, Manitoba (Meglis et al, 2005). In claystones, however, the strong wave attenuation make them almost undetectable. The only opportunity to detect them is to place acoustic sensors in close proximity to sources. Forney (1999) developed a compact device capable of recording AE reflecting the creation of the damaged zone during the excavation of a gallery in Mont Terri. Claystones might show a natural variability that must be taken into account in the analysis of velocity variations induced by damage. A solution to overcome this problem is to measure the velocity of the waves in the rock before it was damaged and monitor its evolution during the excavation of the build. This technique called "velocity survey" has been implemented several times during the excavation of shafts (Balland et al, 2009), galleries or slots. It allowed characterizing the intensity and extension of the damaged zone, as well as the phenomena occurring during sealing or reconfinement of a fractured rock vicinity. Using a specifically designed 3D device with S and P waves back analysis in the stiffness matrix changes

Estimation des paramètres de modèles cinétiques par mesure des flux d’énergie dans un réacteur double enveloppe

National audienc

Sulfonyl group-containing polyphenylenes as membranes for fuel cells

Sulfonated polyphenylenes contain, as repeating units, I and II, in which R1=3 are H, halo, alkyl, aryl, perfluoroalkyl, and perfluoroaryl; E is a simple bond, -C(:O)-, -P(:O)-, and -SO2-; W1 is arylene or perfluoroarylene; A is =O-, -S-, -NH-, and -NR9- (R is alkyl); W2 is aryl substituted by F, -O-SO2-aryl, -S(:O)-aryl, or perfluoroalkyl; R4-8 are H, halogen, -OH, -M(R10)3 (R10 = alkyl. M is Si, Sn, Ge), -P(:O)(OR11)2 (R11 = alkyl), aryl, -O-aryl, -SO2-aryl, alkylaryl, perfluoroalkyl, perfluoroaryl, alkyl, -O-perfluoroaryl, and perfluoroalkylaryl, in which at least one of R4-8 is -SO3H, -PO3H2, -CO2H (optionally including alkali metal salts), perfluoroalkyl, or perfluoroalkylaryl. The polymers, which have a mol. wt. 50,000 (preferably 50,000-150,000). have application as membranes, esp. for fuel cell

Estimation des paramètres de modèles cinétiques par mesure des flux d’énergie dans un réacteur double enveloppe

National audienc

Sulfonyl group-containing polyphenylenes as membranes for fuel cells

Sulfonated polyphenylenes contain, as repeating units, I and II, in which R1=3 are H, halo, alkyl, aryl, perfluoroalkyl, and perfluoroaryl; E is a simple bond, -C(:O)-, -P(:O)-, and -SO2-; W1 is arylene or perfluoroarylene; A is =O-, -S-, -NH-, and -NR9- (R is alkyl); W2 is aryl substituted by F, -O-SO2-aryl, -S(:O)-aryl, or perfluoroalkyl; R4-8 are H, halogen, -OH, -M(R10)3 (R10 = alkyl. M is Si, Sn, Ge), -P(:O)(OR11)2 (R11 = alkyl), aryl, -O-aryl, -SO2-aryl, alkylaryl, perfluoroalkyl, perfluoroaryl, alkyl, -O-perfluoroaryl, and perfluoroalkylaryl, in which at least one of R4-8 is -SO3H, -PO3H2, -CO2H (optionally including alkali metal salts), perfluoroalkyl, or perfluoroalkylaryl. The polymers, which have a mol. wt. 50,000 (preferably 50,000-150,000). have application as membranes, esp. for fuel cell

Estimation des paramètres de modèles cinétiques par mesure des flux d’énergie dans un réacteur double enveloppe

National audienc

Validation of a low inertia mold with rectangular heating channels for injection process

International audienceCurrent molding processes for high performance composite materials do not meet future expectations of composite manufacturers in terms of cadence, particularly for aeronautics and automotive [1]. Researches are currently being carried out on resin, reinforcements and process automation, with the aim of increasing composite production line productivity for being competitive in terms of cost-quality-cadence. However, current molds are designed according to rules from the field of plastic injection, which leads to massive structures and low thermal performances [2]. For efficiency on the complete production line, it is essential to conduct research on molds to increase their thermomechanical responses. In a previous study [3], it was demonstrated that the transition from circular to rectangular heating channels, with consideration of technological aspects (pump and pressure drops) could significantly increase heating rates of the structure. The main purpose of this study is to experimentally validate thermal performances of an innovative low inertia mold with rectangular channels compared to a massive reference RTM mold as presented in Figure 1

Thermomechanical optimization of an innovative low inertia mold with rectangular heating channels

International audienceIn order to be able to meet industries expectations, especially aeronautical and automotive industries, in terms of production rate, aspect and structural quality for high performance composite injected parts, it is necessary to produce reactive and thermally efficient molds. The objective of this study is to lead a thermomechanical optimization on an innovative low thermal inertia mold with rectangular heating channels. The optimized structure is compared with a reference : a massive conventional mold with circular heating channels. The finite elements model setting up for this study take into account technological constraints related to pressure drop and the use of a pump for fluid circulation. Obtained results highlight the importance of taking into account these technological constraints in the mold design. Thus, according to the choosen heating technology, water or oil heating, the optimized model of the low thermal inertia mold and with rectangular heating channels allows a reduction of the heating time by a factor of 2 for water heating and by a factor of 8.5 for oil heating

Comparaison topologique de canaux de chauffe d'outillages d'injection pour les matériaux composites

International audienc