Détermination de la durée de vie géochimique du stock de déchets miniers de Carnoulès (France) à partir d\'un modèle hydrodynamique.

Le stock de déchets miniers de Carnoulès forme un aquifère bicouche constitué de sable très fin à sulfure et de sable fin à passage de blocs grossiers. L\'écoulement de l\'eau à l\'intérieur est guidé par un drain souterrain. Le modèle hydrodynamique a permis d\'évaluer les flux de matières à partir de la reconstitution de débits à l\'exutoire. Les fortes teneurs en sulfates de l\'eau observées à la source proviennent de la dissolution de la pyrite qui détermine l\'essentiel des réactions géochimiques à l\'intérieur du stock de déchets miniers. La durée de vie du stock de déchets miniers estimée à partir des flux annuels de pyrite oxydée est de plus de 100 ans. Les méthodes de rémédiation appropriées ne doivent donc pas être des installations qui exigeront un entretien continu compte tenue de cette longue durée de vie.The mining waste stock of Carnoulès is a double-layered aquifer made up of very fine clay and sand with sulphide and of sand ends to passage of coarse blocks. The groundwater circulation is guided by an underground drain. The hydrodynamic model made it possible to evaluate matter flows starting from the reconstitution of flows to the catchment discharge system. It arises a strong content sulphate of water coming from the dissolution of the pyrite which guides the main geochemical reactions inside the stock of mining waste. The lifetime considered starting from annual oxidized pyrite flows is of more than 100 years. Methods of remediation should not be installations requiring a Keywords: Drainage acide minier, modélisation, hydrodynamique, Modflow/Mining acid drainage, modelling, hydrodynamics, ModflowSciences & Nature Vol. 4 (1) 2007: pp. 105-11

A pluridisciplinary methodology for intregrated management of coastal aquifer - Geological, hydrogeological and economic studies of the Roussillon aquifer (Pyrénées-Orientales, France)

In order to study Mediterranean coastal water management, a pluridisciplinarity approach is developed. Reservoir geology and some of its tools, used in oil prospecting, are applied to build a detailed sedimentary model. The analysis of depositional environments and sedimentary process allows the correlation of pre-existing data (outcrop, borehole, and seismic profile) using Genetic stratigraphy (onshore domain) and seismic stratigraphy (offshore domain). The interpretation results in a better knowledge of the sedimentary geometries following correlations between onshore and offshore domains. It is thus possible to differentiate the coastal groundwater aquifers precisely and to establish their relative connections. At the same time, hydrogeological investigations such as hydrochemistry and geophysical prospecting allow us to elaborate the hydrogeological conceptual model of the case studies. Variable-density flow and solute transport simulations constitute the hydrogeological work. Experimental economy constitutes the third part of this integrated methodology. It assesses the effectiveness of institutional arrangements to cope with aquifer overexploitation. Feed-back from these three fields of research will also authenticate our methodology. This approach applied on Roussillon basin (South-west of French Mediterranean coastline) could be exported to many other coastal area

A portable and affordable extensional rheometer for field testing

Extensional shear testing is often needed to characterise the behaviour of complex fluids found in industry and nature. Traditional extensional rheometers are typically expensive, fragile and heavy and are only suited to making measurements in a laboratory environment. For some applications, it is necessary to make in situ rheological measurements where, for example, fluid properties change rapidly over time or where laboratory facilities are unavailable. This paper reports the development and validation of an inexpensive, lightweight and robust 'open source' extensional rheometer, Seymour II. Validation was carried out experimentally and computationally. Measurements on a Newtonian fluid (492 mPa s Brookfield silicone oil) yielded results of 510  ±  51 mPa s; these are comfortably within the range of  ±10% which other authors have quoted for extensional techniques using laboratory rheometers. Comparison of the observed filament thinning dynamics to those obtained using computational fluid dynamics (CFD) gave good qualitative agreement. Use of Seymour II at the University of Cambridge Botanic Gardens revealed that the mucilage of the 'crane flower', $\textit{Strelitzia reginae}$, was a viscoelastic fluid whose extensional response could be described by a two-mode Giesekus equation. Engineering drawings and image analysis code for Seymour II are available for download at the project website, www.seymourII.org/.Support for a summer internship for NP from ENSTA, a PhD studentship for MPB from Sandvik Hyperion and Ceratizit, and a PhD studentship for OMM from Chemours

A broadband microwave amplifier using multilayer technology

In this paper, we propose a new broadband microwave amplifier structure using multi layer technology. Thus the design of multilayer interconnections, with combined slotlines and microstriplines, improves the integration of a feedback passive cell and permits to obtain a broadband balanced amplifier without increasing the circuit area. A first part details the structure design and the conception of this feedback cell. In a second part, the method is performed for a microwave amplifier design considering a GaAs FET commonly used in microwave circuits. A large frequency bandwidth of about 500MHz around 4 GHz is obtained. The results concerning the input VSWR, the output one and the gain are then presented. In conclusion the amplifier performances are satisfying and the feasibility of such a structure with the use of the multilayer interconnections is then evidenced

Study of fracturing in the southern sector of Sierra Almijara (province of Málaga)

4 páginas, 3 figuras.-- Trabajo presentado en la 37ª Sesión Científica, Almería, 2004.By means of a photointerpretation study, the main fault sets have been determined in the Sierra Almijara, in the Betic Cordillera. The more frequent directions are N20-40E, N50-70E, N90-100E, N120-140E and N140-160E. They are consistent with some of the main stress fields occurred in the Betic Cordillera. The paleostresses responsible of fracturing have been inferred from regional and field data. Many of the movements of these faults occurred since de late Tortonian, during a very important uplifting of the Betic Range, up to the Quaternary.Este trabajo es una contribución al proyecto «Estudio regional del karst de Almijara», financiado por la Fundación Cueva de Nerja, así como al Grupo de Investigación 308 de la Junta de Andalucía.Peer reviewe

A chaotic direct sequence spread-spectrum system for underwater communication

International audienceThe recent advances in acoustic modem technology have enabled the development of Underwater Acoustic Networks (UAN). Application interests include oceanographic information gathering, environmental monitoring or coastal defense. Due to its ability of simultaneously sharing the same frequency band for various users and the poor propagation conditions usually encountered in shallow water environment, the Code Division Multiple Access (CDMA) is a promising scheme for UAN. Recent results show that a standard CDMA direct-sequence spread spectrum approach is not sufficient to ensure Low Probabilities of Detection (LPD) and/or Interception (LPI), that is an unauthorized observer may notice that a communication signal is present. For many applications, this drawback is not acceptable. In this paper, the application of chaos to transmission of information is under investigation to achieve an LPI/LPD objective in an UAN context. Performance results of two receivers are shown for a single user through a realistic simulation scenario. An experiment at sea will be conducted by GESMA soon to confirm these first results

A methodology for extreme groundwater surge predetermination in carbonate aquifers: Groundwater flood frequency analysis

The present paper introduces a methodology devoted to groundwater flooding hazard assessment. It focuses on groundwater floodings due to water table rises that are induced by heavy rainfall events. This special kind of flooding can cause devastating damages, particularly in fractured and karstified carbonate aquifers. Indeed, hydrodynamic conditions prevailing in these heterogeneous formations can involve strong groundwater surges. The developed methodology shows how flood frequency analysis methods can be applied in groundwater flood frequency analysis. Actually, it consists in estimating the T-year hydraulic head that characterizes the T-year groundwater surge, given a return period T. It also aims at defining the rainfall events likely to cause such extreme groundwater surges. This methodology was applied within the framework of a building construction project in a karstic Mediterranean aquifer located in Southern France. The present paper is designated to be a first contribution to groundwater flood frequency analysis. This new field of research has to be further developed in order to put forward consensus guidelines for hydrogeologists and decision-makers as in flood frequency analysis

Effect of fast drainage in karst sinkholes on surface runoff in Larzac Plateau, France

International audienceStudy region: A 1 km² mountainous karst watershed on the Larzac Plateau in Southern France.Study focus: The village of La Vacquerie, located at the outlet of the watershed, is punctually affected by flash floods during storm events. On the contrary, no runoff is observed in the village during other rainfalls. A sinkhole, draining surface flows at the entrance of the village, plays a role on these differences. Descriptions of short and intense rainfalls in 2015 (avg. 40 mm/h over 5 h) and long and light events in 2014/2016 (avg. 8 mm/h over 25 h) provide valuable data to calibrate inputs of a distributed physic-based flow model, in particular the sinkhole drainage capacity. This study aims to quantify drainage capacity changes with rainfall characteristics and to find the rain intensity threshold at which runoff exceeds sinkhole capacity.New hydrological insights for the region: The hydrological water balance of the hydrosystem is affected by the intensity variations for each of the different rain events. It shows the limited part of drainage in sinkhole (10%) during long light rains but its significant increase (40%) during short and intense rains. Drainage in sinkhole is affected by intensity variations rather than by the total amount of precipitation. When intensity exceeds 110 mm/h the sinkhole is submerged. However, this result is obtained in a case of Plateau configuration, where the saturated level, located deep below the surface (here 500 m), does not retro-affect drainage in the sinkhole