Etude hydrogéologique des séries triasiques dans la région de Jeffara-Dahar (Sud Tunisien): Apport des diagraphies et de la sismique réflexion

The present study concentrates on the interpretation of well logs and seismic reflection data in the Jeffara- Dahar region (Southeast part of Tunisia) for a better characterization of the Triassic aquifer, a potential target of water supply. Lithological columns and their corresponding well logs reveal that Sidi Stout, Kirchaou and Touareg sandstones as well as Mekraneb and Rehach dolomites are the main reservoirs of the Triassic aquifer. Well log analysis highlights many permeable and fractured layers that could play an important role in the groundwater circulation. The interpreted seismic sections and the resulting isochrone maps show a tectonic influence on the Triassic aquifer geometry in the Jeffara-Dahar region. The normal faulting of E-W and NW-SE accidents created an aquifer compartmentalized by raised and tilted blocks. Seismic cross-sections reveal that this structure controls the depth of permeable formations and the circulation of groundwater. These results will be useful for rationalising the future hydrogeological research that will be undertaken in the Jeffara-Dahar area.[fr] La présente étude concerne l’interprétation des données de la sismique réflexion et celles des puits y compris les enregistrements diagraphiques en vue d’une meilleure caractérisation de l’aquifère triasique de la région de Jeffara-Dahar (Sud-Est de la Tunisie) qui constitue une cible potentielle pour l’alimentation en eau. Les logs lithologiques associés aux enregistrements diagraphiques correspondants montrent que les principaux réservoirs sont les grés de Sidi Stout, Kirchaou et Touareg ainsi que les dolomies de Mekraneb et Rehach. L’interprétation diagraphique met en évidence des niveaux de faible perméabilité et d’autres perméables et bien fracturées qui pourraient jouer un rôle dans l’acheminement des eaux souterraines. Les profils sismiques interprétés et la cartographie élaborée en conséquence mettent en évidence que l’aquifère triasique est compartimenté en blocs soulevés et affaissés. Cette structuration, contrôlée par la réactivation des accidents E-W et NW-SE en failles normales au cours du Trias, influence l’épaisseur des formations perméables ainsi que le sens d’écoulement de la nappe d’eau. Les résultats obtenus seront utiles pour la rationalisation des futures recherches hydrogéologiques dans la région de Jeffara – Dahar

Well dispersed fractal aggregates as filler in polymer-silica nanocomposites: long range effects in rheology

We are presenting a new method of processing polystyrene-silica nanocomposites, which results in a very well-defined dispersion of small primary aggregates (assembly of 15 nanoparticles of 10 nm diameter) in the matrix. The process is based on a high boiling point solvent, in which the nanoparticles are well dispersed, and controlled evaporation. The filler's fine network structure is determined over a wide range of sizes, using a combination of Small Angle Neutron Scattering (SANS) and Transmission Electronic Microscopy (TEM). The mechanical response of the nanocomposite material is investigated both for small (ARES oscillatory shear and Dynamical Mechanical Analysis) and large deformations (uniaxial traction), as a function of the concentration of the particles. We can investigate the structure-property correlations for the two main reinforcement effects: the filler network contribution, and a filler-polymer matrix effect. Above a silica volume fraction threshold, we see a divergence of the modulus correlated to the build up of a connected network. Below the threshold, we obtain a new additional elastic contribution of much longer terminal time than the matrix. Since aggregates are separated by at least 60 nm, this new filler-matrix contribution cannot be described solely with the concept of glassy layer (2nm)

Deep structure in the Bir M’Chergua region (North-East of Tunisia). Hydrogeological implications

The Bir M’Chergua region, located fifty kilometers from the capital Tunis, is an important economic pole in Tunisia. However, the water shortage resulting from many successive drought periods has led to a significant degradation of the various industrial, tourist and agricultural activities in this region. Groundwater exploitation can alleviate this situation, but it requires a better characterization of aquifers. In this context, the present study aims to provide precisions on the Bir M’Chergua hydrogeological scheme by determining the subsurface structures from gravimetric data interpretation. Residual anomaly, vertical derivative and total horizontal gradient maps are calculated from the Bouguer anomaly to identify and delimit the causative sources. The Euler deconvolution technique is also applied to estimate these sources depth. The structural map resulting from gravimetric interpretation highlights buried structures and discontinuities of different direction and depth that can greatly influence the Bir M’Chergua aquifer system geometry and functioning. In fact, the highlighting of tectonic features at more than 1500 m depth around the Jebel Oust dome explains the origin and the high salinity of the thermal waters in this sector; such tectonic accidents have favored a deep penetration of the recharge water as well as their contact with the Triassic terrains

Geological and Hydrothermal Outlines of the Tunisian Fluorine Province (North-Eastern Tunisia)

ABSTRACT Compilation and treatment of geological, hydrostratigraphical, geophysical and hydrogeothermical information's are very important to assess natural resources of the sedimentary basin which is characterized by its extension, geology and hydrodynamism. Hydrochemical investigation is necessary to more understanding the relationship between thermal circulation, mineral deposits and the water -rock interaction. The chemical composition of the thermal waters seems to be controlled by the Triassic evaporate and influenced by the mineral deposits. Especially, the Fluorite deposits result from hydraulic fracturing and suggest the presence of active hydrothermal system and high temperatures in deep aquifers

Hybrid core@soft shell particles as adhesive elementary building blocks for collaidal crystals

Hybrid materials have been developed through the synthesis of colloidal silica surrounded by elastomer polymer brushes. These core@shell materials have been achieved by the use of "nitroxide-mediated polymerization" (NMP) associated with a "grafting from" method. The living and controlled characteristics of the polymerization allow TEM observations of well-monodisperse core@shell nanohybrids. We present herein the synthetic process to create homogeneous smoothness particles surface associated with a strong adhesive property. The brush thickness is tuned in order to compare with molecular dynamic equations through the tailoring of the grafting density and the molecular weight. Finally, these particles were used as elementary adhesive building blocks and self-assembled by a dip-coating process to form a monolayered material. Its diffraction under light is described on a large-scale material as well as the elastomeric polymer brushes layer influence