排序方式： 共有78条查询结果，搜索用时 0 毫秒
71.
Hard rocks or crystalline rocks (i.e., plutonic and metamorphic rocks) constitute the basement of all continents, and are particularly exposed at the surface in the large shields of Africa, India, North and South America, Australia and Europe. They were, and are still in some cases, exposed to deep weathering processes. The storativity and hydraulic conductivity of hard rocks, and thus their groundwater resources, are controlled by these weathering processes, which created weathering profiles. Hard-rock aquifers then develop mainly within the first 100 m below ground surface, within these weathering profiles. Where partially or noneroded, these weathering profiles comprise: (1) a capacitive but generally low-permeability unconsolidated layer (the saprolite), located immediately above (2) the permeable stratiform fractured layer (SFL). The development of the SFL’s fracture network is the consequence of the stress induced by the swelling of some minerals, notably biotite. To a much lesser extent, further weathering, and thus hydraulic conductivity, also develops deeper below the SFL, at the periphery of or within preexisting geological discontinuities (joints, dykes, veins, lithological contacts, etc.). The demonstration and recognition of this conceptual model have enabled understanding of the functioning of such aquifers. Moreover, this conceptual model has facilitated a comprehensive corpus of applied methodologies in hydrogeology and geology, which are described in this review paper such as water-well siting, mapping hydrogeological potentialities from local to country scale, quantitative management, hydrodynamical modeling, protection of hard-rock groundwater resources (even in thermal and mineral aquifers), computing the drainage discharge of tunnels, quarrying, etc.
相似文献72.
Dehydration of dioctahedral aluminous phyllosilicates: thermodynamic modelling and implications for thermobarometric estimates 总被引：1，自引：1，他引：0
Benoît Dubacq Olivier Vidal Vincent De Andrade 《Contributions to Mineralogy and Petrology》2010,159(2):159-174
We propose a solid-solution model for dioctahedral aluminous phyllosilicates accounting for the main compositional variations,
including hydration, observed in natural smectites, interlayered illite/smectite, illites, and phengites from diagenetic to
high-grade metamorphic conditions. The suggested formalism involves dehydrated micas and hydrated pyrophyllite-like thermodynamic
end-members. With these end-members, the equilibrium conditions of quartz + water + K-bearing mica-like phyllosilicates of
fixed 2:1 composition are represented by a line in P–T space along which the interlayer water content varies. The relevant thermodynamic properties required for the calculation
of equilibrium conditions were derived using a set of 250 natural data of known maximal temperature and pressure conditions,
which covers a range between 25°C and few MPa to 800°C and 5 GPa. The temperatures calculated at fixed pressure with our model
are in fair agreement with those reported in the literature for the 250 natural data. At low temperature and pressure, the
amount of interlayer water in K-deficient phengite and illite is predicted to reach 100% of the apparent vacancies, which
is consistent with previous values reported in the literature. Although the amount of interlayer water is predicted to decrease
with pressure and temperature, it is calculated to be significant in K-deficient phengite from LT–HP pelites metamorphosed
at about 350°C, 10 kbar. The presence of molecular water in the interlayer site of such phengites has been confirmed by FTIR
mapping. Its implications for P–T estimates are discussed. 相似文献
73.
This paper is a presentation of an European project called RISK-UE, entitled: “An advanced approach to earthquake risk scenarios with applications to different European towns”. It gives the origin, the objectives and the organisation of the project, together with the content of the different workpackages comprising methodological aspects: different features of European town, seismic hazard, urban system exposure, vulnerability of current, historical and monumental buildings, vulnerability of lifelines and essential facilities, seismic risk scenario, with an application to the seven following cities: Barcelona, Bitola, Bucharest, Catania, Nice, Sofia and Thessaloniki. These studies were realized in close relation with the decisionmakers of these cities, in order that they implement Risk Management Plans and Plans of Action to effectively reduce seismic risk. 相似文献
74.
Smail Slimani Nicolas Massei Johanna Mesquita Danièle Valdés Matthieu Fournier Benoît Laignel Jean-Paul Dupont 《Hydrogeology Journal》2009,17(8):1823-1832
The temporal variability of water-level fluctuations in the chalk aquifer of Upper Normandy, France is constrained by natural climate fluctuations and is closely linked to the regional geological patterns. The chalk plateaus are covered with 5–50 m thick semi-permeable surficial formations; the thickness of the underlying chalk aquifer varies from 50 to 300 m. The relationship among climate oscillations, piezometric levels, and geologic structure were investigated by correlation, Fourier spectral, and continuous wavelet analyses of selected piezometric time-series data. Analysis focused on two piezometers located on the uplifted side of a major fault and two piezometers on the downthrown side. After generalization to other piezometers in the region, it was deduced that, in the downthrown compartments, a substantial aquifer and surficial formations thickness would imply a strong attenuation of annual variability, while multi-year variability is clearly expressed. Conversely, in the uplifted compartments, a thin layer of surficial formations and small thickness of the chalk authorizes strong variations on the annual mode with respect to the contribution of long-term climatic oscillations (multi-year variability). The results then demonstrated—and proposed a spatial determination of—the differential influence of geological patterns on the filtering of climate-induced oscillations in piezometric variability. 相似文献
75.
György Hetényi Benoît Taisne Fanny Garel Étienne Médard Sonja Bosshard Hannes B. Mattsson 《Bulletin of Volcanology》2012,74(2):457-482
Columnar jointing is a common feature of solidified lavas, sills and dikes, but the factors controlling the characteristic
stoutness of columns remain debated, and quantitative field observations are few in number. In this paper, we provide quantitative
measurements on sizing of columnar joint sets and our assessment of the principal factors controlling it. We focus on (1)
chemistry, as it is the major determinant of the physical (mechanical and thermal) properties of the lava, and (2) geology,
as it influences the style of emplacement and lava geometry, setting boundary conditions for the cooling process and the rate
of heat loss. In our analysis, we cover lavas with a broad range of chemical compositions (from basanite to phonolite, for
six of which we provide new geochemical analyses) and of geological settings. Our field measurements cover 50 columnar jointing
sites in three countries. We provide reliable, manually digitized data on the size of individual columns and focus the mathematical
analysis on their geometry (23,889 data on side length, of which 17,312 are from full column sections and 3,033 data on cross-sectional
area and order of polygonality). The geometrical observations show that the variation in characteristic size of columns between
different sites exceeds one order of magnitude (side length ranging from 8 to 338 cm) and that the column-bounding polygons’
average order is less than 6. The network of fractures is found to be longer than required by a minimum-energy hexagonal configuration,
indicating a non-equilibrium, geologically quick process. In terms of the development and characteristic sizing of columnar
joint sets, our observations suggest that columns are the result of an interplay between the geological setting of emplacement
and magma chemistry. When the geological setting constrains the geometry of the emplaced body, it exerts a stronger control
on characteristic column stoutness. At unconstrained geometries (e.g. unconfined lava flows), chemistry plays the major role,
resulting in stouter columns in felsic lavas and slenderer columns in mafic lavas. 相似文献
76.
Bénédicte Fruneau Benoît Deffontaines Jean-Paul Rudant Anne-Marie Le Parmentier 《Comptes Rendus Geoscience》2005,337(13):1173-1183
The Saint-Lazare area in Paris (France) has undergone important water pumping for the construction of the underground Haussmann–Saint-Lazare station for the EOLE subway line. This paper presents the monitoring of the small surface displacements related to this pumping activity, by classical SAR interferometry. Piezometric measurements provided on 87 piezometers by SNCF and IGC as well as precise levelling data acquired on 626 points by SNCF are also examined. Their comparison with interferometric results shows their good agreement and complementarity, as well as the potential ‘operationality’ of SAR interferometric approach in such a study. To cite this article: B. Fruneau et al., C. R. Geoscience 337 (2005). 相似文献
77.
78.
Benoît Laignel Emmanuel Dupuis Alain Durand Jean-Paul Dupont Emmanuel Hauchard Nicolas Massei 《Comptes Rendus Geoscience》2006,338(8):556-564
An accurate quantification of erosion, based on high-frequency monitoring of river discharge and suspended sediment fluxes is proposed for two watersheds in the western Paris Basin, a sensitive area with respect to erosion phenomena. This continuous monitoring makes it possible to include flood events of short duration, but significant erosion potential. The obtained erosion rate (16 and 21 t?km?2?yr?1) is among the weakest of the planet (3.5 to 18?000 t?km?2?yr?1). However, this annual balance does not reflect the behaviour of these rivers which can be torrential in certain cases. To cite this article: B. Laignel et al., C. R. Geoscience 338 (2006). 相似文献