Finite element analysis of the effect of corrosion on the behavior of reinforced earth walls     

Truong‐Linh Chau  Emmanuel Bourgeois  Alain Corfdir 《国际地质力学数值与分析法杂志》2012,36(15):1741-1756

A simple model for the corrosion‐induced loss of stiffness and strength of the steel strips of earth‐reinforced walls was introduced in a finite element simulation of the long‐term behavior of the wall, in which the backfill‐strips interactions are taken into account by means of a generalized homogenization procedure (called a multiphase model). The results show an initial phase of slow displacements induced by the loss of stiffness, followed after a few decades by a steep acceleration of the displacements, leading to wall failure. The influences of the parameter controlling corrosion, the backfill cohesion and the heterogeneity of the corrosion process are discussed. Results are used to discuss a strategy for reinforced earth wall surveillance. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Evaluation of antifouling properties of non-toxic marine paints     

Abdellatif Mellouki  Armand Bianchi  Alain Perichaud  Georges Sauvet 《Marine pollution bulletin》1989,20(12):612-615

The most common way to prevent biofouling of immersed surfaces is to coat the exposed surfaces with a paint containing a biocide acting on marine organisms by diffusion into the surrounding water. However diffusion of toxins into the marine environment causes pollution and serious economic problems. This paper outlines the anti-microfouling properties of some insolubilized quaternary ammonium salts (grafted onto a vinyl copolymer by means of a covalent non-hydrolyzable bond). After immersion times in sea-water up to 4 months, the microbial cover was limited to bacterial forms, without microalgae or cyanobacteria as observed on the untreated, or tin-salt painted surfaces. Bacteria are mostly on unicell forms and numerous areas appear free of any microorganisms. As microbiofouling is an obligate step to macrofouling, this unleachable antifouling treatment could result in a prolonged protection.  相似文献   

The December 4, 1983 to February 18, 1984 eruption of Piton de la Fournaise (La Reunion, Indian Ocean): Description and interpretation     

Jean-Franois Lnat  Patrick Bachlery  Alain Bonneville  Pascal Tarits  Jean-Louis Chemine  Hugues Delorme 《Journal of Volcanology and Geothermal Research》1989,36(1-3)

On December 4, 1983 an eruption started at vents located 1.5 km southwest of the summit of Piton de la Fournaise at the base of the central cone. After 31 months of quiescence this was one of the longest repose period in the last fifty years. The eruption had two phases: December 4 to January 18 and January 18 to February 18. Phase 1 produced about 8 × 10⁶ m³ of lava and Phase II about 9 × 10⁶ m³. The erupted lava is an aphyric basalt whose mineralogical and geochemical composition is close to that of other lavas emitted since 1977.The precursors of the December 4 outbreak were limited to two-week shallow (1.5–3 km) seismic crisis of fewer than 50 events. No long-term increase was noted in the local seismicity which is very quiet during repose periods and no long-term ground inflation preceded the eruption. Outbreaks of Phases I and II were preceded by short (2.5 hours and 1.5 hours) seismic swarms corresponding to the rise of magma toward the surface from a shallow reservoir. Large ground deformation explained by the emplacement of the shallow intrusions, was recorded during the seismic swarms. A summit inflation was observed in early January, before the phase II outbreak, while the phase I eruption was still continuing.Piton de la Fournaise volcanological observatory was installed in 1980. Seismic and ground deformation data now available for a period of 4 years including the 1981 and the 1983–1984 eruptions, allow us to describe the physical behavior of the volcano during this period. These observations lead us to propose that the magma transfer from deep levels to the shallow magma reservoir is not a continuous process but a periodic one and that the shallow magma reservoir was not resupplied before the 1981 and 1983–1984 eruptions. Considerations on the eruptive history and the composition of recent lavas indicate that the reservoir was refilled in 1977.  相似文献   

Dynamic faulting under rate-dependent friction   总被引：2，自引：0，他引：2  

Alain Cochard  Raúl Madariaga 《Pure and Applied Geophysics》1994,142(3-4):419-445

We discuss the effects of rate-dependent friction on the propagation of seismic rupture on active faults. Several physicists using Burridge and Knopoff's box and spring model of faulting have proposed that fault complexity may arise from the spontaneous development of a self-similar stress distribution on the fault plane. If this model proves to be correct, it has important consequences for the origin of the complexity of seismic sources. In order to test these ideas on a more realistic earthquake model, we developed a new boundary integral equation method for studying rupture propagation along an antiplane fault in the presence of nonlinear rate-dependent friction. We study rupture dynamics of models with single and twin asperities. In our models, asperities are places on the fault with a higher value of prestress. Othewise all fault parameters are homogeneous. We show that for models with such asperities, a slip velocity weakening friction leads to the propagation of supersonic healing phases and to the spontaneous arrest of fracture if the prestress outside the asperities is low enough. For models with asperities, we can also observe narrow slip velocity pulses, qualitatively similar to the so-called Heaton pulses observed in some earthquake accelerograms. We also observe a complex distribution of stress after the rupture that depends on details of the initial distribution of asperities and on the details of the friction law.  相似文献   

Late Quaternary kinematics of the Pallatanga strike-slip fault (Central Ecuador) from topographic measurements of displaced morphological features   总被引：2，自引：0，他引：2  

Thierry Winter  Jean-Philippe Avouac  Alain Lavenu 《Geophysical Journal International》1993,115(3):905-920

The northeast-trending Pallatanga right-lateral strike-slip fault runs across the Western Cordillera connecting N50E-N70E trending normal faults in the Gulf of Guayaquil with N-S reverse faults in the Interandean Depression. Over most of its length, the fault trace has been partly obscured by erosional processes and can be inferred in the topography only at the large scale. Only the northern fault segment, which follows the upper Rio Pangor valley at elevations above 3600 m, is prominent in the morphology. Valleys and ridges cut and offset by the fault provide an outstanding record of right-lateral cumulative fault displacement. The fault geometry and kinematics of this particular fault segment can be determined from detailed topographic levellings. The fault strikes N30E and dips 75 to the NW. Depending on their size and nature, transverse morphological features such as tributaries of the Rio Pangor and intervening ridges, reveal right-lateral offsets which cluster around 27 ± 11m, 41.5 ± 4 m, 590 ± 65 m and 960 ± 70 m. The slip vector deduced from the short-term offsets shows a slight reverse component with a pitch of about 11.5 SW. The 41.5 ± 4 m displacements are assumed to be coeval with the last glacial termination, yielding a mean Holocene slip-rate of 2.9- 4.6 mm yr⁻¹. Assuming a uniform slip rate on the fault in the long term, the 27 m offset appears to correlate with an identified middle Holocene morphoclimatic event, and the long term offsets of 590 m and 960 m coincide with the glacial terminations at the beginning of the last two interglacial periods.  相似文献   

The 15 m.y. geomagnetic reversal periodicity: a quantitative test     

Alain Mazaud  Carlo Laj 《Earth and Planetary Science Letters》1991,107(3-4)

We have analyzed the three most commonly used geomagnetic polarity time scales that cover the past 100 m.y.. In the three cases, different spectral analyses show a 13–16 m.y. periodicity in the rate of reversal occurrence. To test whether this periodicity is real or simply arises from a random generator we have compared these polarity time scales with a large number of synthetic sequences produced by a random process, characterized by a linear time variation of its mean activity. Geomagnetic and generated sequences were regularly sampled by using sliding windows, anf then the Fourier spectra of the obtained frequency signals were compared. This test shows that the detected periodicity is presumably not a simple statistical fluctuation of an aperiodic generator, and consequently that a long-term periodicity in the geodynamo must be seriously considered.  相似文献   

Twin structure in coesite studied by high resolution electron microscopy     

Alain Bourret  E. Hinze  H. D. Hochheimer 《Physics and Chemistry of Minerals》1986,13(3):206-212

A synthetic crystal of coesite, SiO₂, has been found to contain microtwins. The (100) reflection twin has been made evident on incoherent (010) planes. The twin structure is directly imaged by high resolution electron microscopy at 2,5 Å resolution, allowing an atomic model to be proposed. This twin could be incoherent on large surfaces and the dislocation density is predicted. The X-ray crystallographic data are analyzed critically in view of the presence of such defects in single crystals. The mutual orientation between a silicon matrix and coesite precipitates in Czochralski-silicon annealed specimens is proposed to be non unique as a consequence of the easy twinning of coesite.  相似文献   

Turbulent heat fluxes by profile and inertial dissipation methods: analysis of the atmospheric surface layer from shipboard measurements during the SOFIA/ASTEX and SEMAPHORE experiments     

Hélène Dupuis  Alain Weill  Kristina Katsaros  Peter K. Taylor 《Annales Geophysicae》1995,13(10):1065-1074

Heat flux estimates obtained using the inertial dissipation method, and the profile method applied to radiosonde soundings, are assessed with emphasis on the parameterization of the roughness lengths for temperature and specific humidity. Results from the inertial dissipation method show a decrease of the temperature and humidity roughness lengths for increasing neutral wind speed, in agreement with previous studies. The sensible heat flux estimates were obtained using the temperature estimated from the speed of sound determined by a sonic anemometer. This method seems very attractive for estimating heat fluxes over the ocean. However allowance must be made in the inertial dissipation method for non-neutral stratification. The SOFIA/ASTEX and SEMAPHORE results show that, in unstable stratification, a term due to the transport terms in the turbulent kinetic energy budget, has to be included in order to determine the friction velocity with better accuracy. Using the profile method with radiosonde data, the roughness length values showed large scatter. A reliable estimate of the temperature roughness length could not be obtained. The humidity roughness length values were compatible with those found using the inertial dissipation method.  相似文献   

Detailed gravity study of the offshore structure of Piton de la Fournaise volcano,Reunion Island     

Dominique Rousset  Alain Bonneville  Jean-François Lenat 《Bulletin of Volcanology》1987,49(6):713-722

We present an interpretation of gravity data acquired in 1984 by the French R/V Jean Charcot on the submarine part of the eastern flank of Piton de la Fournaise volcano. We comment on the Bouguer anomaly map and give a quantitative interpretation of three gravity profiles. The main results are that a gravity high over Grand Brûlé, the lower subaerial part of the eastern flank, does not extend far offshore and that an anomalous topographic feature, discovered in 1982 on the submarine eastern flank, is characterized by a large negative anomaly. We propose three hypotheses to explain the origin of this anomaly, i. e., it marks the site of a new volcano, or it is a consequence of lateral volcanism from a volcano older than Piton de la Fournaise, or more probably, it represents a great landslide deposit.  相似文献   

Trace metal adsorption modelling and particle-water interactions in estuarine environments     

Alain C.M. Bourg 《Continental Shelf Research》1987,7(11-12)

A brief, critical review of empirical and conceptual metal adsorption models is presented. This covers models conditional to seawater chemistry, as well as models applicable to estuaries or other systems of variable solution chemistry. The conceptual surface complexation approach is used to show why desorption of trace metals does not necessarily occur readily in estuaries, and why in some cases adsorption can even take place. The relevance and weaknesses of this model for the understanding of the mobility and fate of heavy metals in turbid environments, as related to particle dynamics, is discussed using the macrotidal Gironde Estuary, France, as the example.  相似文献