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141.
The unsaturated poromechanical behavior of Callovo-Oxfordian argillite (also referred to as Meuse/Haute–Marne argillite) is
analyzed by means of indentation tests at different hygrometries. Numerical simulations carried out with a finite element
code are then used to simulate flat punch indentation tests at different controlled hygrometries. The numerical response F(h) is compared to experimental data in order to estimate the drained Young’s modulus E and the internal friction angle
\Upphi\Upphi (at high confinement) by means of a back analysis. A linear decrease in the drained Young’s modulus and quasi-constant values
of the internal friction angle are observed when the relative humidity ranges. Some predictions of the model are also presented
to quantify the activation of hydraulic phenomena. Indeed, the maximal variation of the saturation and porosity relative to
the initial state of the specimen are lower than 10% and 8%, respectively. 相似文献
142.
Weathering of sandstone lotus petals at the Angkor site: a 1,000-year stone durability trial 总被引:1,自引:1,他引:0
Marie-Françoise André Bruno Phalip Olivier Voldoire Franck Vautier Yves Géraud Mhammed Benbakkar Christophe Constantin Fabienne Huber Gilles Morvan 《Environmental Earth Sciences》2011,63(7-8):1723-1739
This article is based on field investigations carried out at Ta Keo and Banteay Srei temples (Angkor, Cambodia), which have similar environmental histories and display the same recurrent decorative pattern (lotus petal) in three different sandstone lithotypes. Based on two original scales of mechanical and chemical weathering, the degree of deterioration of c.2000 sandstone petals was visually assessed, resulting in the proposal of a durability scale. An explanatory scheme was provided, based on laboratory analyses of stone materials (ICP-AES, XRD, SEM-EDS, polarizing microscopy and mercury injection). The key drivers of sandstone durability are both mineralogical and petrophysical. The remarkable preservation of the pink sandstone is due to the quartzose nature of its clasts, the non-swelling clay content of its abundant matrix (kaolinite) and its porosity structure (large connected pores and probable non-connected porosity). The overall good preservation of the green sandstone is due to its extremely low porosity and specific surface area, associated with its strong cementation. The severe deterioration of the grey sandstone is due to its laminated structure (oriented biotites), the susceptibility to hygric swelling and solution of its binding agents (chlorite/smectite and calcite) and its porosity structure, which evolves during a two-stage weathering sequence. The first stage is characterized by a bimodal porosity due to the partial clogging of macropores by swelling clays, and the second stage by a substantial increase in porosity and the penetration of salts (barite and anhydrite). Conversely, oxidation phenomena associated with weathering can lead to a drastic reduction of porosity. 相似文献
143.
S��bastien Migeon Antonio Cattaneo Virginie Hassoun Christophe Larroque Nicola Corradi Francesco Fanucci Alexandre Dano Bernard Mercier de Lepinay Fran?oise Sage Christian Gorini 《Marine Geophysical Researches》2011,32(1-2):225-243
Based on new multibeam bathymetric data, seismic-reflection profiles and side-scan sonar images, a great number of submarine failures of various types and sizes was identified along the northern margin of the Ligurian Basin and characterized with 3 distinct end-members concerning their location on the margin, sedimentary processes and possible triggering mechanisms. They include superficial landslides mainly located in the vicinity of the main mountain-supplied rivers and on the inner walls of canyons (typically smaller that 108 m3 in volume: Type 1), deep scars 100?C500 m high along the base of the continental slope (Type 2), and large-scale scars and Mass Transport Deposits (MTDs) affecting the upper part of the slope (Type 3 failures). The MTDs are located in different environmental contexts of the margin, including the deep Var Sedimentary Ridge (VSR) and the upper part of the continental slope in the Gulf of Genova (Finale Slide and Portofino Slide), with volumes of missing sediment reaching up to 1.5 × 109 m3. High sedimentation rates related to hyperpycnal flows, faults and earthquake activity, together with sea-level fluctuations are the main factors invoked to explain the distribution and sizes of these different failure types. 相似文献
144.
The paper presents an overview of the recent contributions of centrifuge modelling to the understanding of soil-structure interaction and the development of design and predictive methods in the field of mobile jack-up drilling rig foundations. Both advantages and limitations of the centrifuge methods are detailed and key examples are presented. The benefits provided by centrifuge modelling to the development of analysis methods that are now being used within the jack-up industry are highlighted. To conclude, industry trends and research opportunities are discussed, as is the possible role of the geotechnical centrifuge in finding solutions to these new needs. 相似文献
145.
Hubert Gall��e Alexandre Trouvilliez C��cile Agosta Christophe Genthon Vincent Favier Florence Naaim-Bouvet 《Boundary-Layer Meteorology》2013,146(1):133-147
For the first time a simulation of blowing snow events was validated in detail using one-month long observations (January 2010) made in Adélie Land, Antarctica. A regional climate model featuring a coupled atmosphere/blowing snow/snowpack model is forced laterally by meteorological re-analyses. The vertical grid spacing was 2 m from 2 to 20 m above the surface and the horizontal grid spacing was 5?km. The simulation was validated by comparing the occurrence of blowing snow events and other meteorological parameters at two automatic weather stations. The Nash test allowed us to compute efficiencies of the simulation. The regional climate model simulated the observed wind speed with a positive efficiency (0.69). Wind speeds higher than 12 m s ?1 were underestimated. Positive efficiency of the simulated wind speed was a prerequisite for validating the blowing snow model. Temperatures were simulated with a slightly negative efficiency (?0.16) due to overestimation of the amplitude of the diurnal cycle during one week, probably because the cloud cover was underestimated at that location during the period concerned. Snowfall events were correctly simulated by our model, as confirmed by field reports. Because observations suggested that our instrument (an acoustic sounder) tends to overestimate the blowing snow flux, data were not sufficiently accurate to allow the complete validation of snow drift values. However, the simulation of blowing snow occurrence was in good agreement with the observations made during the first 20 days of January 2010, despite the fact that the blowing snow flux may be underestimated by the regional climate model during pure blowing snow events. We found that blowing snow occurs in Adélie Land only when the 30-min wind speed value at 2 m a.g.l. is >10 m s ?1. The validation for the last 10 days of January 2010 was less satisfactory because of complications introduced by surface melting and refreezing. 相似文献
146.
Alexandre Ganachaud Alexander Sen Gupta Jaclyn N. Brown Karen Evans Christophe Maes Les C. Muir Felicity S. Graham 《Climatic change》2013,119(1):163-179
Future physical and chemical changes to the ocean are likely to significantly affect the distribution and productivity of many marine species. Tuna are of particular importance in the tropical Pacific, as they contribute significantly to the livelihoods, food and economic security of island states. Changes in water properties and circulation will impact on tuna larval dispersal, preferred habitat distributions and the trophic systems that support tuna populations throughout the region. Using recent observations and ocean projections from the CMIP3 and preliminary results from CMIP5 climate models, we document the projected changes to ocean temperature, salinity, stratification and circulation most relevant to distributions of tuna. Under a business-as-usual emission scenario, projections indicate a surface intensified warming in the upper 400 m and a large expansion of the western Pacific Warm Pool, with most surface waters of the central and western equatorial Pacific reaching temperatures warmer than 29 °C by 2100. These changes are likely to alter the preferred habitat of tuna, based on present-day thermal tolerances, and in turn the distribution of spawning and foraging grounds. Large-scale shoaling of the mixed layer and increases in stratification are expected to impact nutrient provision to the biologically active layer, with flow-on trophic effects on the micronekton. Several oceanic currents are projected to change, including a strengthened upper equatorial undercurrent, which could modify the supply of bioavailable iron to the eastern Pacific. 相似文献
147.
The National Road RN 91 has been threatened for about twenty-five years by a huge landslide, located 25 km south-east to the town of Grenoble (France). If several million cubic meters of rock fall down, the debris will dam the valley. Then the failure of the dam by overtopping and rapid erosion might result in a catastrophic flood and dramatic consequences for human life, environment and economy throughout the valley. The paper presents the hazard assessment based on geological and hydrological surveys, including small scale hydraulic tests, as well as the risk evaluation that has been performed. The risk management relies first upon a high level monitoring and an emergency plan; various mitigation strategies have been considered. 相似文献
148.
Christophe Nkem Kamel Hammami Idriss Yacoub Halalaw Luc Calvin Owono Owono Nejm-Eddine Jaidane 《Astrophysics and Space Science》2014,349(1):171-179
We report on ab initio coupled-cluster calculations of the interaction potential energy surface for the HCNH+–He complex. The aug-cc-pVTZ Gaussian basis, to which is added a set of bond functions placed at mid-distance between HCNH+ center of mass and He atom is used. The HCNH+ bonds length are set to their values at the equilibrium geometry, i.e., r e [HC]=1.0780 Å, r e [CN]=1.1339 Å and r e [NH]=1.0126 Å. The interaction energy presents a global minimum located $266.9~\mathrm{cm^{-1}}$ below the HCNH+–He dissociation limit. Using the interaction potential obtained, we have computed rotational excitation cross sections in the close-coupling approach and downward rate coefficients at low temperature (T≤120 K). It is expected that the data worked out in this study may be beneficial for further astrophysical investigations as well as laboratory experiments. 相似文献
149.
Cédric Cotté Christophe Guinet Isabelle Taupier-Letage Bruce Mate Estelle Petiau 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(5):801-811
Since the heterogeneity of oceanographic conditions drives abundance, distribution, and availability of prey, it is essential to understand how foraging predators interact with their dynamic environment at various spatial and temporal scales. We examined the spatio-temporal relationships between oceanographic features and abundance of fin whales (Balaenoptera physalus), the largest free-ranging predator in the Western Mediterranean Sea (WM), through two independent approaches. First, spatial modeling was used to estimate whale density, using waiting distance (the distance between detections) for fin whales along ferry routes across the WM, in relation to remotely sensed oceanographic parameters. At a large scale (basin and year), fin whales exhibited fidelity to the northern WM with a summer-aggregated and winter-dispersed pattern. At mesoscale (20–100 km), whales were found in colder, saltier (from an on-board system) and dynamic areas defined by steep altimetric and temperature gradients. Second, using an independent fin whale satellite tracking dataset, we showed that tracked whales were effectively preferentially located in favorable habitats, i.e. in areas of high predicted densities as identified by our previous model using oceanographic data contemporaneous to the tracking period. We suggest that the large-scale fidelity corresponds to temporally and spatially predictable habitat of whale favorite prey, the northern krill (Meganyctiphanes norvegica), while mesoscale relationships are likely to identify areas of high prey concentration and availability. 相似文献
150.
Pierre Ocvirk Ariane Lançon Christophe Pichon Philippe Prugniel Damien Le Borgne Brigitte Rocca-Volmerange Michel Fioc Caroline Soubiran Eric Thiébaut 《Astrophysics and Space Science》2003,284(2):933-936
We present inversion techniques which aim at recovering the composite nature and the kinematics of a stellar population from
its high resolution absorption line spectrum. The originality of the combined inversion is its potential to recover both the
stellar content and the kinematics simultaneously. These techniques use new synthetic high resolution spectra produced by
PéGASE and minimization algorithms. We apply them to mock data representing the bulge and disk population of the inner region
of spiral galaxies.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献