Improving Short- and Long-term Stability of Underground Gypsum Mine Using Partial and Total Backfill   总被引：1，自引：0，他引：1  

Mohamed Marwan Al Heib  Christophe Didier  Farimeh Masrouri 《Rock Mechanics and Rock Engineering》2010,43(4):447-461

The stability of underground mines represents a key issue for active and abandoned mines. Over the last few years, several collapses of underground mines in France have affected existing buildings and infrastructures. Many factors are generally identified as the cause of failures: pillar ageing, fractures, and pillars’ height to width ratio, etc. Among the treatment techniques available to prevent instability and reduce the deterioration of pillars, backfill is the most frequently used. A research programme, supported by the French Ministry of the Environment, was developed to study the operability of partial and total backfill using waste material in the Livry-Gargan gypsum mine (near Paris, France), where pillar height is 17 m. The paper focuses on: (1) the characterisation of the gypsum and fill material (laboratory and in situ tests), (2) the in situ measurements, involving 5 pillars equipped with 19 pressure cells, since 1999, (3) and numerical modelling of fractured pillars performed in order to improve understanding of the effects of backfill on the stability of room-and-pillar mines. The study clearly shows the operability and the advantages of partial and total backfill for short-term pillar stability. The induced horizontal pressure generated by backfill can reach 200 kPa. The use of numerical modelling also shows the effect of backfill on fractures and that backfill reduces indicatively the shear displacement and the opening of fractures. Numerical modelling helps in identifying the mechanisms of backfill and in a better understanding of the behaviour of backfilled mines.  相似文献   

Surface exposure dating and geophysical prospecting of the Holocene Lauvitel rock slide (French Alps)     

Romain Delunel  Didier Hantz  Régis Braucher  Didier L. Bourlès  Philippe Schoeneich  Jacques Deparis 《Landslides》2010,7(4):393-400

Large rock falls and rockslides represent a risk for human communities in mountainous areas as they can cause fatalities and destruction of settlements and infrastructures. Assessing the associated hazard requires constraining the time frequency of such events. Since large rockslides are not common, estimating their frequency requires recording them over a long period of time. The Holocene period then appears as pertinent, which implies that rockslide features have to be dated with absolute chronology methods. This paper presents a characterisation and dating of the Lauvitel rockslide, one of the largest Holocene rockslides in the French Alps. Combining field observation with electrical tomography profiles performed on the rockslide deposit that constitutes the Lauvitel Lake dam allows estimating its volume at a minimum of 12?×?10⁶?m³. In addition, cosmic ray exposure dating using in situ-produced ¹⁰Be concentration measurements has been applied to date seven samples collected both on the main sliding surface and on blocks lying on the dam and further downstream. Ages obtained are consistent with a single large rockslide event, which occurred at 4.7?±?0.4 ¹⁰Be-ka and formed two distinct deposits. However, from a mechanical point of view, these clearly separated deposits could hardly result from a single movement. A comparison of their reach angles with those reviewed in the literature highlights that the lower deposit must result from rock avalanches larger than 10⁷?m³, while the upper one (the Lauvitel dam) must result from several events smaller than 10⁶?m³. In the context of hazard assessment for land use planning, these events can, however, be considered as a unique event.  相似文献   

The ultimate summit eruption of Puy de Dôme volcano (Chaîne des Puys,French Massif Central) about 10,700 years ago     

Didier Miallier  Pierre Boivin  Catherine Deniel  Alain Gourgaud  Philippe Lanos  Marie Sforna  Thierry Pilleyre 《Comptes Rendus Geoscience》2010,342(11):847-854

The Puy de Dôme volcano is a trachytic lava dome, about 11,000 y old. New pyroclastic layers originating from the volcano itself were discovered covering the summit and the flanks of the volcano. These pyroclastic layers do not fit with the previous interpretation, assuming a non-explosive dome-forming eruption. The tephra display pyroclastic surge features and exhibit fresh trachytic lapilli, basement lithics, allogeneous basaltic lava and clinker fragments requiring an open vent eruption. This ultimate eruption occurred after a period of rest, long enough for vegetation to develop on the volcano, as evidenced by carbonized plant fragments. Radiocarbon dating of some of these fragments gave an age of c.10,700 y also suggesting a significant rest duration.  相似文献   

Derivation of tropospheric aerosol properties from satellite observations     

Didier Tanré 《Comptes Rendus Geoscience》2010,342(4-5):403-411

Here we review the methods presently available and expected in the near future for retrieving the tropospheric aerosol properties using remote sensing. Since all aerosol properties cannot be derived from space, measurements performed from the surface of the Earth are used to adjust the parameters that are not directly accessible and to limit the variability of the parameters that present a weaker sensitivity. The aerosol properties derived include the column concentration (expressed by the aerosol optical depth), the size (given by distribution of the aerosol in 2 to 3 size modes or measurement of the Angström coefficient), composition (expressed by the refractive index), shape and vertical profile. The article is restricted to aerosols that are within the troposphere since the techniques used for stratospheric aerosols are very specific.  相似文献   

Comparison between the fish communities of lakes, reservoirs and rivers: can natural systems help define the ecological potential of reservoirs?     

Pascal Irz  Mélanie Odion  Christine Argillier  Didier Pont 《Aquatic Sciences - Research Across Boundaries》2006,68(1):109-116

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Response scenarios for the deltaic plain of the Rhône in the face of an acceleration in the rate of sea-level rise with special attention to<Emphasis Type="Italic">Salicornia</Emphasis>-type environments     

Didier Pont  John W. Day  Philippe Hensel  Evelyne Franquet  Frank Torre  Patrick Rioual  Carles Ibànez  Eric Coulet 《Estuaries and Coasts》2002,25(3):337-358

One of the most critical problems facing many deltaic wetlands is a high rate of relative sea-level rise due to a combination of eustatic sea-level rise and local subsidence. Within the Rhône delta, the main source of mineral input to soil formation is from the river, due to the low tidal range and the presence of a continuous sea wall. We carried out field and modeling studies to assess the present environmental status and future conditions of the more stressed sites, i.e.,Salicornia-type marshes with a shallow, hypersaline groundwater. The impacts of management practices are considered by comparing impounded areas with riverine areas connected to the Rhône River. Analysis of vegetation transects showed differences between mean soil elevation ofArthrocnemum fruticosum (+31.2 cm),Arthrocnemum glaucum (+26.5 cm), bare soil (+16.2 cm), and permanently flooded soil (?12.4 cm). Aboveground and belowground production showed that root:shoot ratio forA. fruticosum andA. glaucum was 2.9 and 1.1, respectively, indicating more stressful environmental conditions forA. glaucum with a higher soil salinity and lack of soil drainage. The annual leaf litter production rate of the two species is 30 times higher than annual stem litter production, but with a higher long-term decomposition rate associated with leaves. We developed a wetland elevation model designed to predict the effect of increasing rates of sea-level rise on wetland elevation andSalicornia production. The model takes into account feedback mechanisms between soil elevation and river mineral input, and primary production. In marshes still connected to the river, mineral input decreased quickly when elevation was over 21 cm. Under current sea-level rise conditions, the annual amount of riverine mineral input needed to maintain the elevation of the study marshes is between 3,000 and 5,000 g m^?2 yr^?1. Simulations showed that under the Intergovernmental Panel on Climate Change best estimate sea-level rise scenario, a mineral input of 6,040 g m^?2 yr^?1 is needed to maintain marsh elevation. The medium term response capacity of the Rhône deltaic plain with rising sea level depends mainly on the possibility of supplying sediment from the river to the delta, even though the Rhône Delta front is wave dominated. Within coastal impounded marshes, isolated from the river, the sediment supply is very low (10 to 50 g m^?2 yr^?1), and an increase of sea-level rise would increase the flooding duration and dramatically reduce vegetation biomass. New wetland management options involving river input are discussed for a long-term sustainability of low coastal Mediterranean wetlands.  相似文献   

Organic petrology and geochemistry of the Carboniferous coal seams from the Central Asturian Coal Basin (NW Spain)     

No Piedad-Snchez  Isabel Surez-Ruiz  Luis Martínez  Alain Izart  Marcel Elie  Didier Keravis 《International Journal of Coal Geology》2004,57(3-4):211-242

This paper presents for the first time a petrological and geochemical study of coals from the Central Asturian Coal Basin (North Spain) of Carboniferous (Pennsylvanian), mainly of Moscovian, age. A paleoenvironmental approach was used, taking into account both petrographic and organic geochemical studies. Vitrinite reflectance (R_r) ranges from 0.5% to 2.5%, which indicates a high volatile bituminous to semianthracite and anthracite coal rank. The coal samples selected for paleoenvironmental reconstruction are located inside the oil–gas-prone phase, corresponding to the interval between the onset of oil generation and first gas generation and efficient expulsion of oil. This phase is represented by coals that have retained their hydrocarbon potential and also preserved biomarker information. Paleodepositional reconstruction based on maceral and petrographic indices points to a swamp environment with vitrinite-rich coal facies and variable mineral matter content. The gelification index (GI) and groundwater influence index (GWI) indicate strong gelification and wet conditions. The biomarkers exhibit a high pristane/phytane ratio, suggesting an increase in this ratio from diagenetic processes, and a high diterpanes ratio. This, in turn, would seem to indicate a high swamp water table and a humid climate. The maximum point of coal accumulation occurred during the regressive part of the Late Moscovian sequence and in the most humid climate described for this period of time in the well-known coal basins of Europe and North America.  相似文献   

On the Role of Lightning NOx in the Formation of Tropospheric Ozone Plumes: A Global Model Perspective     

Didier Hauglustaine  Louisa Emmons  Mike Newchurch  Guy Brasseur  Toshinori Takao  Kouji Matsubara  James Johnson  Brian Ridley  Jeff Stith  James Dye 《Journal of Atmospheric Chemistry》2001,38(3):277-294

A series of ozone transects measured each year from 1987 to 1990 over thewestern Pacific and eastern Indian oceans between mid-November andmid-Decembershows a prominent ozone maximum reaching 50–80 ppbv between 5 and 10 kmin the 20° S–40° S latitude band. This maximum contrasts with ozonemixing ratios lower than20 ppbv measured at the same altitudes in equatorial regions. Analyses witha globalchemical transport model suggest that these elevated ozone values are part ofa large-scale tropospheric ozone plume extending from Africa to the western Pacific acrosstheIndian ocean. These plumes occur several months after the peak in biomassburninginfluence and during a period of high lightning activity in the SouthernHemispheretropical belt. The composition and geographical extent of these plumes aresimilar to theozone layers previously encountered during the biomass burning season in thisregion.Our model results suggest that production of nitrogen oxides from lightningstrokes sustains the NO_x (= NO+NO₂) levels and the ozonephotochemical productionrequired in the upper troposphere to form these persistent elevated ozonelayers emanating from biomass burning regions.  相似文献   

Heterogeneous distribution of paramagnetic radicals in insoluble organic matter from the Orgueil and Murchison meteorites     

Laurent Binet  Didier GourierSylvie Derenne  François Robert 《Geochimica et cosmochimica acta》2002,66(23):4177-4186

An electron paramagnetic resonance (EPR) investigation was performed on the insoluble organic matter from the Orgueil and Murchison meteorites and on terrestrial coals with similar elemental composition. A complementary electron nuclear double resonance (ENDOR) study was also carried out. The measured g-factors of the observed paramagnetic radicals in the meteoritic organic matter exhibit a similar correlation with the chemical composition as for the type III (i.e., hydrogen-poor) terrestrial coals. The main result, obtained from EPR saturation and ¹H ENDOR enhancement measurements, showed that the effective local concentration in radicals of about 3 to 4 × 10¹⁹ spin.g⁻¹ in the meteoritic organic matter is much higher than the average concentration, hence the occurrence of radical-rich regions accounting for 5% and 20% of the total volume for Murchison and Orgueil, respectively. This heterogeneity of concentration seems to be unique among natural organic macromolecules. It is proposed that these radical-rich regions correspond to pristine parts of the organic matter synthesized in conditions close to those prevailing in the interstellar medium, and which have survived the hydrothermal process on the parent body.  相似文献   

Non-linear Langevin model of geomorphic erosion processes   总被引：1，自引：0，他引：1  

Didier Sornette  Yi-Cheng Zhang 《Geophysical Journal International》1993,113(2):382-386

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