Shear behavior of geotextile-reinforced Chlef sand in the Mediterranean region: Laboratory investigation     

Sidali Denine  Sadok Feia  Rawaz Dlawar Muhammed  Jean Canou  Jean-Claude Dupla 《Marine Georesources & Geotechnology》2013,31(5):599-608

Abstract

An experimental study about the effects of initial conditions of soil and geotextile reinforcement on the mechanical behavior of reinforced sand is presented in this paper. A series of direct shear tests are conducted on reconstituted specimens of dry and moist natural sand prepared with different initial water content (w?=?0, 1.5, 3, and 5%) and including the two arrangements of geotextile layers (one and two layers, respectively). Both S41 and PEC55types of non-woven geotextile were used and placed at different heights of the specimens to investigate the effect of geotextile reinforcement on the behavior of sand. Test specimens were prepared at Dr =80% of relative density and were subjected to three different normal stresses of 100, 200, and 300?kPa. The experimental results showed that the deposition mode (wet and dry) and the geotextile reinforcement have significant effects on the behavior of reinforced sand. The increase in shear strength is relatively more significant for specimens prepared with dry deposition mode as compared to those prepared with wet deposition mode and it increases with the number of geotextile layers, this effect becomes less significant for wet specimens. The experimental results also demonstrated that (PEC55) non-woven geotextile shows a better performance than the (S41) of geotextile. These results can be explained by the effective tensile strength property of polyester yarns of the (PEC55) non-woven geotextile that it has led to a significant increase in the shear strength.  相似文献   

Cosmogenic Be dating of a sackung and its faulted rock glaciers, in the Alps of Savoy (France)     

Jean-Claude Hippolyte  Didier Bourls  Rgis Braucher  Julien Carcaillet  Laëtitia Lanni  Maurice Arnold  Georges Aumaitre 《Geomorphology》2009,108(3-4):312-320

Sackungs are the largest gravitational deformation observed in mountains. They are characterized by the long-term slowness of the movements, but their mechanism is still not well understood. Nowadays cosmic ray exposure (CRE) dating methods allow dating the morphologic structures involved in sackung and can contribute at the understanding of their origin. In the Alps, the 5.3 km long Arcs sackung initiated during the activity of rock glaciers. Three samples from these faulted rock glaciers provide their first CRE ages and show that at 2000 m elevation these block accumulations moved during the Younger Dryas and stopped in early Holocene. Six ¹⁰Be ages of fault scarps show that the Arcs sackung lasted only a few thousand years and stopped at about 8462 ± 432 ¹⁰Be yr. They also reveal that deformation migrated upslope in agreement with a mechanism of flexural toppling of vertical layers. This unique and long gravitational event, characterized by migration of the deformation, does not support earthquake shaking as triggering mechanism for individual faults. It shows that, in the upper Isère valley, slope deformation was delayed of several thousand years after glacial debuttressing, and is not anymore active despite its fresh morphology.  相似文献   

Interactions between Cd,Cu, Pb,and Zn and four different mine soils     

Lotfi Mouni  Lazhar Belkhiri  Abdelkrim Bouzaza  Jean-Claude Bollinger 《Arabian Journal of Geosciences》2017,10(4):77

The chemical associations of Cd, Cu, Pb, and Zn in four mine soil samples from the Amizour-Bejaia Pb/Zn mine (Algeria) have been investigated by a five-step sequential extraction procedure. Although Cd preferentially binds to carbonates, Cu, Pb, and Zn are mainly associated with the organic and reducible fractions. Batch adsorption experiments with either mono- or multi-metallic solutions are described with the Freundlich isotherm model. Whatever the nature of the soil sample, the sorption behavior for each given metal except Pb is very similar, indicating that the binding sites at the soil surface are progressively occupied by the metal from the solution. On each soil sample, the decreasing order of sorption can be established as Pb >> Cu > Cd > Zn. When the four metals are simultaneously applied to each soil sample, their specific behavior is strongly affected by their interactions and/or competition for the available surface sites: we generally observed isotherm curves with a slight maximum before the plateau at higher solution concentration. Although Cu is only slightly affected by the other metals, in the case of Pb, Cd, and Zn, the sorbed amounts strongly decreased.  相似文献   

The main characteristics, problems, and prospects for Western European coastal seas   总被引：1，自引：0，他引：1  

Dauvin JC 《Marine pollution bulletin》2008,57(1-5):22-40

Located to the far West of Western Europe, France has a western maritime coastal zone of more than 3800 km, which is widely influenced by the North-eastern Atlantic. The English Channel, an epi-continental shallow sea with very strong tides, runs along 650 km of the French coast and 1100 km of the English coast. It is also a bio-geographical crossroad encompassing a much wider range of ecological conditions than other European seas. France's Atlantic coast north of the Gironde estuary is a succession of rocky and sandy shorelines, including a sizeable intertidal zone, a wide continental shelf, and two major estuaries (Loire and Gironde). South of the Gironde, the 260 km of coastline is low, sandy and straight, with a narrowing continental shelf further on South due to the presence of the Cape Breton canyon in the bathyal and abyssal zones. Interface between the continental and oceanic systems, these bordering seas--North Sea, English Channel and Atlantic Ocean--have been the subject of many recent research programmes (the European Mast-FLUXMANCHE and INTERREG programmes; the national coastal environment programme and the LITEAU programme in France), designed to improve comprehension of the functions, production, and dynamics of these seas as well as their future evolution. Given the many conflicting practices in these littoral zones, integrated coastal zone management appears to be essential in order to cope with both natural phenomena, such as the infilling of estuarine zones, cliff erosion, and rising sea levels, and chronic anthropogenic pressures, such as new harbour installations (container dikes, marinas), sea aggregate extraction for human constructions, and offshore wind mill farms. This article provides as complete an overview as possible of the research projects on these bordering seas, both those that have recently been accomplished and those that are currently in progress, in order to highlight the main characteristics of these ecosystems and to underline the future challenges for European marine research in terms of the integrated coastal zone management of these highly significant coastal zones.  相似文献   

Comments on Muxika et al. "using historical data, expert judgement and multivariate analysis in assessing reference conditions and benthic ecological status, according to the European Water Framework Directive" [Marine Pollution Bulletin 55 (2007) 16-29     

Ruellet T  Dauvin JC 《Marine pollution bulletin》2008,56(6):1234-1235

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The thermal structure and thickness of continental roots   总被引：19，自引：0，他引：19  

C. Jaupart  J. C. Mareschal 《Lithos》1999,48(1-4):93-114

We compare heat flow data from the Precambrian shields in North America and in South Africa. We also review data available in other less well-sampled Shield regions. Variations in crustal heat production account for most of the variability of the heat flow. Because of this variability, it is difficult to define a single average crustal model representative of a whole tectonic province. The average heat flow values of different Archean provinces in Canada, South Africa, Australia and India differ by significant amounts. This is also true for Proterozoic provinces. For example, the heat flow is significantly higher in the Proterozoic Namaqua–Natal Belt of South Africa than in the Grenville Province of the Canadian Shield (61 vs. 41 mW m⁻² on average). These observations indicate that it is not possible to define single value of the average heat flow for all provinces of the same crustal age. Large amplitude short wavelength variations of the heat flow suggest that most of the difference between Proterozoic and Archean heat flow is of crustal origin. In eastern Canada, there is no good correlation between the local values of heat flow and heat production. In the Archean, Proterozoic and Paleozoic provinces of eastern Canada, heat flow values through rocks with the same heat production are not significantly different. There is therefore no evidence for variations of the mantle heat flow beneath these different provinces. After removing the local crustal heat production from the surface heat flow, the mantle (Moho) heat flow was estimated to be between 10–15 mW m⁻² in the Archean, Proterozoic and Paleozoic provinces of eastern Canada. Estimates of the mantle heat flow in the Kaapvaal craton of South Africa may be slightly higher (≈17 mW m⁻²). Large-scale variations of bulk crustal heat production are well-documented in Canada and imply significant differences of deep lithospheric thermal structure. In thick lithosphere, surficial heat flow measurements record a time average of heat production in the lithospheric mantle and are not in equilibrium with the instantaneous heat production. The low mantle heat flow and current estimates of heat production in the lithospheric mantle do not support a mechanical (conductive) lithosphere thinner than 200 km and thicker than 330 km. Temperature anomalies with surrounding oceanic mantle extend to the convective boundary layer below the conductive layer, and hence to depths greater than these estimates. Mechanical and thermal stability of the lithosphere require the mantle part of the lithosphere to be chemically buoyant and depleted in radiogenic elements. Both characteristics are achieved simultaneously by partial melting and melt extraction.  相似文献   

SOLAR RESEARCH FROM SCHIZOPHRENIA TO UNITY – (Special Historical Review)     

Pecker  Jean-Claude 《Solar physics》1999,184(1):1-39

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Variations in ground surface temperature histories in the Thompson Belt, Manitoba, Canada: environment and climate changes     

Chantal Gosselin  Jean-Claude Mareschal   《Global and Planetary Change》2003,39(3-4):271-284

Several temperature–depth profiles recorded at Pipe Mine, 32 km southwest of Thompson, Manitoba, in central Canada, exhibit a marked departure from the equilibrium gradient. These profiles could be interpreted as indicating strong warming (up to 4.5 K) of the ground surface during the last 200 years. All the temperature profiles at Pipe Mine show perturbations stronger than at the others sites in the Thompson Nickel Belt. Temperature profiles recorded near the town of Thompson show a moderate warming (≈1–2 K) trend, while temperature profiles at Soab, 45 km southwest of Pipe Mine, indicate very moderate cooling (≈0.5 K). There was little human activity in this part of Manitoba before the development of the mining camp of Thompson in the late 1950s. Our study shows the variability of ground surface temperature histories at a very local scale (i.e. <1 km) with much stronger signals at some of the Pipe Mine drill holes than at others. These holes are located within 500 m of the highway and a power line built after 1955, at ≈3 km from the now abandoned open pit mine. The ground surface temperature history (GSTH) obtained by the inversion of Pipe Mine temperature profiles suggests that a recent (50 years) and strong (≈1–2 K) ground surface warming is superimposed on a 1–2 K warming trend that started 200 years ago, without any indication of a cold (little ice ages) episode before. The recent warming (40 years) at Pipe Mine is only a local effect and is likely to be related to the presence of the highway. Before 1960, the ground surface temperature history for Pipe is similar to other sites in the Thompson region. Ground surface temperature histories from other profiles within and near the city of Thompson seem less affected by environmental perturbations and their trends are parallel to that of the meteorological records in the Canadian Prairies.  相似文献   

Ground temperature histories in eastern and central Canada from geothermal measurements: evidence of climatic change     

Hugo Beltrami  Alan M. Jessop  Jean-Claude Mareschal   《Global and Planetary Change》1992,6(2-4)

Inverse and direct methods have been used to analyze a large number of borehole temperature logs in order to infer past climatic changes. Results indicate a warming of 1–2°C in eastern and central Canada during the past 150 years. A period of cooling between 500 and 200 years before present, corresponding to the time of the “Little Ice Age”, has also been identified in the same areas. A regional ground temperature history is estimated for eastern and central Canada from the simultaneous inversion of several temperature logs. The inferred temperature changes appear correlated with the concentration of atmospheric carbon dioxide as reported from a Greenland ice core, and agree with existing meteorological and dendrochronological records for the area.  相似文献   

An analytical electron microscopy (AEM) investigation of opaque inclusions in some type 6 ordinary chondrites     

Hugues LEROUX  Jean-Claude DOUKHAN  Franois GUYOT 《Meteoritics & planetary science》1996,31(6):767-776

Abstract— A large number of ordinary chondrites contains micron-sized particles of metal and/or troilite dispersed in their silicate grains. Such metallic phases are responsible for the so-called darkening of the silicate grains and might be either precipitates, which formed during reduction of the silicates, or inclusions injected as a melt during a shock event. We have investigated these tiny foreign phases by analytical transmission electron microscopy in three unweathered, metamorphosed ordinary chondrites (Saint Séverin, LL6, Tsarev, L6 and Kernouvé, H6). We also looked for remnant shock indices. Our TEM observations suggest the following sequence of events in the three meteorites. First, a number of relatively strong shock events occurred on the parent body/bodies producing an Fe-FeS melt that was injected into silicate grains along a dense network of open fractures. Most of these shock defects were subsequently erased by high-temperature (700–900 °C) thermal metamorphism. Some remnants of the shock events are the observed trails of tiny metal and/or sulfide inclusions that formed as a result of fracture healing. Chemical homogenization of the silicates and limited oxidation of the metallic blebs also occurred during this high-temperature annealing event, resulting in Ni-rich inclusions. This effect was especially pronounced in the L and LL-chondrites studied. During subsequent cooling of the body/bodies, inclusions of chromite and phosphate precipitated, nucleating preferentially on lattice defects (dislocations, subgrain boundaries) and on the metal and sulfide inclusions. A later shock event of moderate intensity, probably corresponding to the separation of the meteorite from its parent body, produced new shock features in the silicate grains of the Saint Séverin meteorite, including mechanical twins in diopside and straight free screw dislocations in olivine.  相似文献