Caractérisation minéralogique et géotechnique des argiles marneuses gonflantes de la région de Médéa,Algérie

This paper presents the approach followed for the geological, mineralogical, and geotechnical characterization of swelling marly clays in the Médéa region. This investigation is conducted in order to estimate the swelling potential of this marly clay layer. The studied sites, located at about 80 km south of Algiers, Algeria, cover an area of approximatively 400 hectares. Five sites are considered. In the first step, the geological, tectonic, climatic, and hydrological contexts of the region are described. According to the geological map of Médéa, most of the formations encountered in the area are composed of Miocene layers represented by marly clays (Fig. 2). This region is characterized by its high and low temperature in summer and winter, respectively, and variable humidity (Fig. 3). In a second step, the results of geotechnical studies, X-ray diffraction tests, chemical analyses, and scanning electron microscope (SEM) observations are presented (Figs. 3, 4, 5, 6, 7, 8, 9). The soils contain quartz (20–26 %), calcium carbonates (11–55 %), kaolinite (8–13 %), illite (6–14 %) and Montmorillonite (18–26 %). The study of their microstructure by means of SEM indicates that these soils are formed by a compact marly clay matrix that is relatively homogeneous and oriented in the dip direction of bedding. A grain size analysis shows that the clay content varies between 17 and 70 %. The water content of all samples varies between 8 and 30 %. The values of the liquidity limit (LL) and plasticity index (PI) vary between 28–76 % and 16–36 % respectively, indicating a highly plastic soil; this is also confirmed by a specific surface varying between 99 and 179 m²/g. The dry density γ _d varies between 15 and 19 kN/m³. The swelling potential of the marly clay samples is evaluated firstly using various indirect methods. In literature, a number of empirical classifications are proposed by different authors (BRE 1980; Chen 1988; Komornik and David 1969; Seed et al. 1962; Snethen 1984; Vijayvergiya et Ghazzaly 1973 et Williams and Donaldson 1980). The swelling potential is related to certain physical properties of soils, such as consistency limits, clay content, methylene blue value, etc. In general, these methods indicate that all the tested soils have a high swelling potential, which confirms the results of mineralogical analysis. Secondly, direct measurements of swelling parameters are performed. Swelling tests are carried out using a standard slaved one-dimensional odometer using two methods: free swell and constant volume, according to standard ASTM D 4546-90 and AFNOR (1995). The swell pressure, the swell percentage and the swell index are given in Fig. 16. It is noted that the soils develop very significant swell pressures which vary between 25 and 900 kPa. This is in agreement with the results obtained by empirical methods. This investigation clearly shows that the marly clays of the Médéa region have a high swelling potential. Therefore, taking into account the phenomenon of soil swelling in structure design is essential.     

Les dépôts morainiques holocènes de la zone axiale pyrénéenne: approche déterministe de leur instabilitéà Verdun sur Ariège, (Pyrénées centrales, France)

This paper reports a study of the historic instability of the till deposits in an area of the central Pyrenees between France and Spain upslope of the town of Verdun. The object of the work was to create a model based on the geomorphological and geological mapping of landslides and a geotechnical survey of the instability of the whole of the mountainous slopes of the Domanial Verdun area. The detailed mapping allows the historic landslides to be distinguished from the more recent/active movements which involve volumes of 100,000 to 400,000?m³ of material. In addition, it was possible to assess the areal percentage of the actively slipping zones (5%) compared to the historic slide zones (12%) and the stable areas (78%). Following the European classification, two types of slides were identified in the Verdun study area: (1) historic rotational slides and (2) active translational slides located in the Verdun area at between 1000 and 1250?m altitude. The stability was calculated using the classic "method of slices", subdividing the slipped zone into vertical slices along a suitable cross section. The so-called factor of safety (F) was determined by dividing the moments of resisting forces (M_R) by the moments of driving forces (M_D). The state of limiting equilibrium has a "factor of safety" of 1. The physical parameters of the till deposits of Verdun were established as: unit weight γ=24.9?kN/m³ (calculated using the percentage of gneissic blocks contained in the tills) and porosity n=0.24. The results of 15 triaxial tests in a gravelly sand matrix were plotted in a Lambe diagram following a linear regression model [x=(σ₁+σ₃)/2 and y=(σ₁–σ₃)/2 with sin?φ′ =tan?θ]. From this the friction angle φ′=33°±3 and c′=45±5?kPa were established. The factor of safety calculated for the moraine deposits in the historic slides was 1.44 without water (Hw=0). With a height of water of 7?m, representing 85% of the till thickness, this was reduced to F=1. To achieve a factor of safety of 1.3, the maximum water level within the till should not exceed 2.5?m, representing 65% of the till thickness. Similarly, the factor of safety was calculated for the active slides of another area (shown as section 4 in Fig.?3 in the paper). Using slice number 9 from the middle of the slide, the factor of safety was 1.08 when the height of the water was taken as 90% of the till thickness. This high calculated factor of safety for the height of water is consistent with the slow movement of the actual slides. However, a lower internal cohesion of the till deposits or the presence of a weathered zone would decrease the factor of safety from 1 to 0.8. It is also possible that other parameters, such as the regional seismic activity, could have been sufficient to initiate movement (F<1) during the last 50?years. It is of note that the map of seismic activity shows that more than a 100 earthquakes with magnitudes greater than 3 have occurred in the central Pyrenees since 1660. The paper emphasises the importance of high-quality mapping which identifies and classifies areas of historic and recent instability. From this, a single geotechnical model to calculate the stability can be established. The level of the water is shown to be the critical parameter and of more significance than the variations in the effective friction angle, which itself is more important than variations in the effective cohesion. With this information it is possible to determine those areas where some form of stabilisation and/or drainage of the till deposits is necessary.     

Impacts des aménagements en montagne sur les processus hydrologiques et l’évolution géodynamique des versants (Les Arcs,Savoie, France)

This work focuses on the interaction between human activity in mountainous areas and slope movement hazards. The paper considers the triggering factors and processes of instability in the urbanized area of Les Arcs, an area exploited for mass ski runs and where many debris flows have occurred over the last 40 years. A progressive survey of the geological, geomorphological, hydrological, hydrogeological and climatic contexts is necessary to tackle the complexity of the phenomena. The human impact is considered as well. From the analysis, the geology associated with a specific climate was determined to be the main triggering factor for debris flow hazards. The influence of the glacial and postglacial period on the geomorphological aspects (e.g. steep slopes) and on the mechanical component of the superficial formations is the main factor. Furthermore, an analysis of regional meteorological data over the last 5 decades has emphasized a significant evolution of the climate since the 1960s which resulted in a general increase in temperature, rainfall (with seasonal variations) and the occurrence of extreme weather events, with long term implications for erosion and on water balance. This seems to be exacerbated by recent human activities which have significantly changed the natural environment: deforestation, changes in vegetation, the development of impervious surfaces such as roofs, roads and car parks, the creation of ski runs and the intensive exploitation of the catchment, all of which may have an influence on runoff and erosion affecting the natural surface structure. These changes and their effects on such factors as runoff and erosion have been reviewed and analyzed. In particular, the effects on hydrology have been highlighted by a hydrological modeling created using PCRaster Environmental Software. The hydrology of the Ravoire torrent before the creation of the ski resort was compared with the present configuration of the catchment. The annual water balance model shows that the ski resort generates a significant increase in the river flow compared to that before the change in land use. The parametric analyses undertaken revealed that the deforestation, the development of ski slopes and impervious areas are responsible for the reduction in infiltration inducing runoff. The maximum increase in water flow occurs during periods of natural high water flow (during snow melt) when the risk of debris flows is naturally high. For the last 20 years, this phenomenon has been amplified by the increasing production of artificial snow on the ski runs. Finally, a complementary model was created to consider the effects over a short time scale. The results of this rain event model emphasize the change in the hydrological response of the rivers after rainfall as a consequence of the change in land use. In particular this indicated a rise in the peak flow towards the resort, which may activate erosive processes above the debris flow source areas.      

Différentes déclinaisons de l'aléa liquéfaction: de la cartographie préventive au projet

As part of its Public Service, Applied Research, and Client Service activities, BRGM's Thematic Centre for Natural Geological Risks (NGR) has recently undertaken studies in order to characterize "liquefaction hazard". The paper considers definitions and presents several approaches to liquefaction hazard assessment, demonstrated by several examples. The first approach is a naturalistic one: Hazard assessment is considered in a structured manner by undertaking: – a regional inventory of historic events – mapping of formations susceptible to liquefaction in homogeneous risk areas subject to seimic activity – preventive mapping of the phenomena at local scale The second approach is a semi-deterministic one: It allows to produce a seismic microzonation, considering parametric calculations and charts (Seed's reverse method). This approach can be used also to recommend soil improvements when liquefaction hazard does exist. The third approach is a deterministic approach: It takes into account a 3D geotechnical model of the analysed area, as well as specific charts to produce a liquefaction hazard assessment of soils and an advanced seismic microzonation. This method was used in Guadeloupe and Martinique districts (French Lesser Antilles) ad for the design of a new TGV railway track in the south of France. The proposed methodology relies on the French Association for Earthquake Engineering recommendations and brings some innovative aspects: combined naturalistic and geotechnical analyses for liquefaction hazard assessment, combined chart use and 3D geotechnical modelling for liquefaction hazard microzonation. Apart from the complete analysis of the liquefaction hazard not always being useful, it also demands major resources, and is consequently sometimes broken down into several less-detailed stages. The various examples considered thus form a continuum and are simply variations of a same definition of the liquefaction hazard: where: X, Y and Z=coordinates t=time Δu=interstitial over-pressure σ'_vo=initial effective stress I_L=Iwasaki's liquefaction index     

Essais systématiques de validation de formulations de sable sénégalais pour l'élaboration d'un sable normalisé

Résumé. Au Sénégal, pays en voie de développement, le sable normalisé employé pour la détermination des classes de résistance des ciments est importé. Un inventaire des ressources locales en sable a été conduit pour rechercher un produit de substitution au sable de Leucate. La première phase de l'étude a permis sur la base d'essais d'orientation, de mettre au point un mélange ternaire composé de deux sables roulés et d'un sable de concassage qui remplit les critères requis pour un "sable normalisé CEN". Dans la deuxième phase de l'étude, des essais systématiques croisés ont été menés à Rennes et à Dakar, ils confirment les résultats des essais d'orientation et les valident d'un point de vue statistique. Electronic Publication     

Exploitation piscicole du barrage Guenitra (Oum Toub,Skikda, Algérie)

The breeding of the carp Cyprinus carpio L. in the Guenitra dam (Oum, Toub, Skikda, Algeria) began in 1989 with 800 larvae imported from Hungary. This pilot project in carp breeding aimed to provide a stock of protein resource at low cost, with the purpose of extending the scheme to other water bodies in the area. Studies of the dam and its fauna took place between 1995 and 1999. It was determined that the Guenitra dam is favourable to carp breeding. The experiment can be replicated with success in similar water bodies.

L’élevage de la carpe Cyprinus carpio L. dans le barrage Guenitra (Skikda, Algérie) a vu le jour en 1989 avec l’ensemencement de 800 alevins importés de la Hongrie. Ce projet pilote de carpiculture avait pour objectif la mise en place d’une ressource protéique à moindre coÛt avec l’ambition de sa généralisation à d’autres plans d’eau de la région. Pour cela, nous avons étudié entre 1995 et 1999, l’hydrobiologie du barrage et les réactions biotope‐biocénose‐ichthyofaune en estimant le stock de pêche s’évaluant entre : Carpe grosse tête Ctenopharyngodon idella Val., Carpe herbivore Aristichthys nobilis R et Carpe argentée Hypophtalmichthys molitrix Val. Les résultats obtenus, durant ces trois campagnes (1996/97, 97/98 et 98/99) englobent les paramètres climatologiques, les analyses physico‐chimiques in situ des sels minéraux et en laboratoire et enfin, l’âge et la biométrie des trois espèces de Carpes. Cette étude diagnostic préliminaire montre que le barrage Guenitra est un écosystème tout à fait favorable à la mise en place et l’exploitation d’une activité carpicole. D’autre part, elle permet de consolider l’idée de transfert de ce type d’élevage dans d’autres retenues d’eau ayant un environnement similaire.     

Mud,Dust, and Marougé: Precarious Construction in a Congolese Refugee Camp

This photo essay combines text and images to convey how the Congolese who reside in Nyarugusu, a United Nations refugee camp in Tanzania, interact with and interpret camp architecture. To establish the camps as temporary spaces, the Tanzanian government requires that refugees construct their houses with sundried mud brick and thatched roofs so that they can eventually be destroyed without a trace. The red dirt of their homes and the camp environment colours almost every facet of Nyarugusu residents' lives, adding a sense of dirtiness to the camp. The violence built into the camp architecture is not only contained in its eventual destruction, but also in the ways in which it visibly marks the residents' alienation and subordination in Tanzania.     

éTé翌德国际设计机构

“翌德国际”活跃的创作氛围。凭借对自然、文化与经济环境的高度责任感和洞察力,“翌德国际”以“适用、和谐、动人”为核心创作理念,并在新技术、新材料的运用方面独树一帜。“翌德国际”上海设计机构拥有一批来自法国、新加坡和中国的优秀设计师,以及数位国际、国内著名专家顾问,以多元的国际视野和活跃的原创风格著称。机构近期在中国大陆的代表作有:北京CLASS-建于果岭的上层建筑(望京31、32地块)规划、建筑与景观设计(2004年度“全国人居经典”建筑金奖2003年度上海市优秀规划设计三等奖,北京市规划委员会2003年度居住区优秀规划设…     

Rôle des fluides dans le comportement hydromécanique des roches fracturées hétérogènes: Caractérisation in situ et modélisation numérique

Hydromechanical coupled processes in a shallow fractured rock mass were investigated in situ through field experiments and numerical simulations. The experimental approach consists of performing simultaneous and multi-frequency measurements of fluid pressures and displacements at different points and on different fracture types within a carbonate reservoir. Two kinds of experiments were conducted at the Coaraze Laboratory Site (France):

1. At the fracture network scale, a global hydraulic loading by groundwater level change shows that the coupling between fluid flow and deformation is simultaneously governed by a dual-permeability hydraulic behaviour and a dual-stiffness mechanical behaviour. The following fluid flow and hydromechanical conceptual scheme was established: first, a transient flow only occurs in faults with high permeability; second, when a steady-state flow is reached in faults, water flows from faults into lower permeability bedding planes. The intact rock matrix is practically impervious but the connectivity between the discontinuities is high. When fluid pressure changes occur within the fracture network, the hydromechanical coupling is direct in the highly permeable faults where a pressure change induces a deformation change. No direct hydromechanical coupling occurs within the lower permeability zones where deformation is not directly correlated with pressure changes. This means that the mechanical deformation of the bedding planes and rock matrix is induced by the fault deformation.
2. At the single fracture scale, the hydromechanical behaviour was evaluated by performing hydraulic pulse injection testing. This test was monitored using high-frequency (f = 120 Hz) hydromechanical measurements conducted with innovative fiber-optic borehole equipment. The hydromechanical response is simultaneously monitored at two measuring points spaced about 1 m apart within the plane of the sub-vertical fracture. Observed fluid pressure versus normal displacement curves shows a characteristic loop-shaped evolution in which the paths for loading (pressure increase) and unloading (pressure decrease) are different. The test was evaluated by coupled hydromechanical modelling using a distinct element technique. By matching the loop behaviour, modelling indicates that the pulse pressure increase portion allows the fracture hydromechanical properties to be determined while the pulse pressure decrease portion is strongly influenced by the hydromechanical effects within the surrounding fractured rock mass. A sensitivity study shows that the key parameters to coupled hydromechanical processes in such fracture systems are the initial hydraulic aperture and normal stiffness of the fracture, the stiffness of the rock matrix and the geometry of the surrounding fracture network.

     

Déformations gravitaires post glaciaires en terrains métamorphiques. Comparaison des indices de déformation du versant sud de la Toura (Saint-Christophe-en-Oisans, France) avec le phénomène de rupture interne du versant sud du Mont Sec (Séchilienne, France)

Introduction: The Sechilienne slope movement, near Grenoble, causes a majour risk and is intensively monitored since 1985. An original deformation mechanism has been proposed to explain the data. Some morphologicial similarities have been observed upstream on air photographs of the south slope of la Toura, naer Saint-Christophe-en-Oisans (France). The question is: is the same phenomenon occuring there too? The site of Saint-Chistophe-en-Oisans (France): The site is located in the Vénéon valley, 13?km upstream from Bourg d'Oisans (Fig.?1), under the Pointe de la Toura peak. There is no permanent stream flowing down the slope. The slope is constituted of gneiss of different formations separeted by North-South faults (Fig.?2). The foot of the slope is covered by alluvial deposits. On the slope itself, there are some recent moraines. The average slope angle is 36° (Fig.?6), which is around 10° lower than the mean value of the valley. The slope is much steeper near the crest, which could correspond to the summit scarp of a slope movement. The middle part of the slope is marked by huge transversal cracks with up-facing scarps, alternating with vertical cliffs. The screes are stopped by the up-facing scarps and underline the cracks on air photographs (Fig.?4). The geological structure is dominated by?(Fig.?5): –?north-south fractures corresponding to the main faults and to the foliation; –?hectometric cracks dipping of 65° in direction NE (N60). They show up-facing scarps and determine tilted-looking rock domains, as seen on the side thanks to the cut made by the "Torrent du Diable" stream; –?two less persistent discontinuity families, one dipping 65° toward SE (N 245) and the other one vertical, in direction N 80. The opening of the transversal cracks, their upfacing scarps and their curvature in the central part of the slope suggests a tilting of the slices. This phenomenon could date from the end or from low-level periods of the Würm glacial age (80000 to 10000?yr B.P.) The manual monitoring of five cracks shows that the phenomenon is still slowly active: mean opening 2?mm in two years, maximum 5?mm (Fig.?7 and 8). Tectonic hypothesis (Fig.?9) may explain the genesis of the atypical transversal cracks and will be tested by geochronological studies (fission traces on apatites) and geodetic measurements. The "Internal Rupture" deformation mechanism: The movement of the south slope of Mont-Sec (Séchilienne, France), constituted by micaschists causes a major risk near Grenoble (rockslide, damming of the Romanche valley, floods...), and is monitored since 1985. The main observations are: a settlement near the crest with opening of local cracks, no localised disorders on foot of the slope, the opening of transversal continuous cracks (with up-facing scarps), and the low inclination of the displacement vectors, whose direction is normal to the continuous cracks. A 240?m long investigation gallery revealed the rotation of rigid blocks (up to 80?m large) with opening or shearing of the contact planes (Fig.?10). These data do not fit with classical translationnal mechanisms and indicate a strong structural control. The mean direction of the rock anisotropy is not favourable neither to a generalised toppling mechanism. Data have been modelled with two main continuous joint families issued from the simplified geological model (one is vertical and the other steeply dipping toward the valley). The computation with the distinct elements method (code UDEC) reveals two distinct zones (Fig.?11): the upper zone is settling and horizontally expanding by shearing of the two joints families while the lower zone is retaining it with a "block toppling like" flexion deformation. The simulation reveals a very deep zone of yielding joints (extending down to the valley level), stress accumulations at the foot of each "cliff" of the final topography and important internal stresses inside the blocks in the flexion zone. Combined with the fluctuation of hydraulic conditions, this subcritical state of stress can, at the geological scale of time, induce secondary fracture propagation. The progressive localisation of this time-defered non reversible damaging phenomenon can lead to global failure of the slope on a non predetermined rupture surface. Conclusion: The morphological and structural observation of the gneissic south slope of la Toura (Saint-Christophe-en-Oisans, France) has revealed so many similarities with the Séchilienne case that the proposed mechanism appears to fit here too. Pursuing the studies on this lowly active site where the observation conditions are excellent will help understanding and controlling more dangerous sites like Sechilienne. Moreover, this phenomenon seems to concern many metamorphic slopes of the Alps.     

Arthouse Café

开设在中国杭州一个面积大于三千平方公尺、楼高三层的艺术馆内,Arthouse Café坐落于建筑物的三楼。为配合艺术馆的整体风格,在不受企业风格的限制下,设计师在本案的构思上可度身订造一个最适合咖啡厅的形象。白天供应咖啡,夜晚供应酒精饮料,为场地营造一个崭新和带动感的格调。物体移动和室内空间通常以相反的姿态出现,流动的人体在静态的场地内形成对比。从这个动感的概念出发,设计师在静止的空间加入动感元素,     

Néotectonique et grands mouvements de versant. Le cas de Séchilienne (Isère, France)

In a homogeneous fracture massif, the release of stress related to the last glacial melting induces the opening of fractures inherited from the tectonic history of the rock mass. In some cases subsidence, similar to sagging from uphill facing scarps, occurs. The mechanism can be briefly described as bending of huge rock blades towards the valley, known as cambering. Nowadays the movements are due to climatic phenomena (rains, snow melting, frost, thaw, huge thermal difference) or mechanical ones such as seismic vibrations, the influence of which is generally more difficult to identify. The Séchilienne slope movement is located on the right bank of the river Romanche, about 20 km upstream of Grenoble, in the district of Isère, south east France, and is representative of this kind of phenomenon. This unstable slope has been affected by recurrent rock falls which, according to old records, were already mentioned in the eighteenth century. The rock mass is made of micaschist and psamites of early Palaeozoic age, belong to the external Belledonne alpine range which is still moving up at a rate of a few millimeters per year. As the terrain has had a long and complex geological history, characterized by five tectonic periods, the hazard geometry and slope movement directions are mainly controlled by faults associated with this succession of structural events. Of particular importance is a regional fault called the “faille de la Romanche” which is some 20 km long and extends from Séchilienne westwards to the Vercors limestone ridge and eastwards through the Taillefer massif to reach the Liassic terrain of the Oisans massif near the village of Ornon. This fault is located at the foot of the unstable slope. There are several arguments in favour of a recent movement of the Romanche fault. The first is linked to some regional geomorphological features such as the lozenger shape of the Romanche valley in the Séchilienne area. This feature resembles a pull-apart basin, bordered on the north and south by the Romanche fault and filled with more than 200 m of Quaternary alluvial sediments. In addition, since 1960 eleven earthquakes have affected the villages of Vizille and Séchilienne. One of these, the Laffrey earthquake (11 January 1999), had a magnitude of 3.5 with an epicenter located only 4 km south of the Séchilienne site. The monitoring devices installed on the slope allow an accurate analysis of the widespread displacements which occur in the area. The analysis has led to the establishment of the influence of the local seismicity on the observed movements. Slope displacements measured since 1985 have shown important speed variations between winter and summer and a progressive long term acceleration. A detailed analysis of the daily measurements shows an increase in the displacements from 29 January to 11 February 1999 without any associated rainfall. Moreover, a systematic examination of the successive slope accelerations related to meteoric water supply has shown that, since the 1999 Laffrey earthquake, the acceleration occurred with only a short delay of less than 24 h after the beginning of heavy rainfall compared with the delay of several days which was common before the 1999 earthquake.     

巴黎Frédéric Malle香水新店

这间香水店如同一个小小的方形盒子一般,嵌入在巴黎玛黑区一座古老建筑的底层。整个空间由木质家具和镜面组成,充满了未来感。进入“盒子”内部,木质小格子纵横交错,就像一座座漂浮在空中的神秘小岛和岩洞里的钟乳石,构成了香水展示架、桌子、冷藏陈列柜等等。墙面和天花板由反光的不锈钢面打造而成,明暗之间,真实与虚幻交错掩映,仿佛打造了一个无穷变幻的虚拟空间。架子上放置的香水瓶则在时空和灯光的交错中变成了一个个小点,等待着消费者去探索和发现……     

Impacts de recouvrements de résidus organiques sur des résidus miniers réactifs

Résumé Les résidus miniers constituent aujourd'hui un problème environmental important. En particulier, les résidus miniers à l'origine du drainage minier acide (DMA) sont les résidus provenant de l'exploitation de minerais tels que l'or, le cuivre, le zinc, le plomb, le nickel, ainsi que le charbon, qui contiennent des minéraux sulfurés généralement associés en formation primaire. L'action intensive et prolongée de l'oxygène atmosphérique et de l'eau de pluie sur les minéraux sulfurés résiduaires contenus dans la zone non saturée des haldes minières conduit à une production d'acide sulfurique. L'une des solutions envisagée pour empêcher la formation de la DMA consiste en un recouvrement des résidus miniers par une couche de matériaux afin de les isoler de l'oxygène atmosphérique. Parmi les matériaux pouvant être utilisés, on trouve ceux composés par des résidus organiques qui peuvent eux-mêmes être composés de différents types. Plusieurs études ont déjà mis en évidence l'efficacité de ces matériaux organiques comme barrière à l'oxygène. Un aspect important qu'il reste à étudier a trait aux interactions entre la couche organique (et ses produits de dégradation) avec les résidus oxydés et non oxydés. Le but de cet article est de présenter les mécanismes théoriques de formation de la DMA et l'utilisation de couches de résidus organiques comme moyen d'y remédier. L'interaction entre les couches de résidus miniers et les couches de résidus organiques est aussi discutée compte tenu de l'importance de ce sujet dans les domaines miniers, civils et environnementaux.

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Altération et rupture d'échantillons d'argilite lors de sollicitations thermomécaniques en conditions humides contrôlées

The objective of this work was to undertake creep tests on shale and describe the microtextural phenomena which initiate internal damage/rupture under thermomechanical loading and relative humidity conditions. The CGI test cell is a system developed at the Centre de Geologie de l'Ingénieur specifically to allow observation of the fabric of a thick slide (50×40×5?mm) at different magnifications during the test. The CGI test cell imposes both an axial and a planar strain on the sample. The first step is to prepare a thick slide from a core and to describe its "initial" state. The second stage is to undertake a creep test to rupture, while the third step is to study the fragments of the ruptured material using XRD (X-ray diffractometry), SEM (scanning electron microscopy) and EDS (energy dispersive spectrometry). The samples studied are from the shales of the Callovo-Oxfordian of the Paris Basin, to the south of Bar-le-Duc in the east of France. These rocks consist of clay minerals (illite and kaolinite), quartz, calcite (22.8%), dolomite, feldspar and pyrite (1%). The pyrite is essentially found in the bioclasts. The creep test is carried out under thermomechanical loading with an axial stress of up to 12?MPa and a temperature rising to 80??°C. The relative humidity is maintained at more than 90%. After 33?days the axial strain reached 0.76%, with rupture of the thick slide occurring 10?days later. The deformation was related to the texture/heterogeneity of the rock and occurred mainly along fissuring. Rupture also occurred along bedding planes, particularly where oxidized pyritic bioclasts were present. The chemical phenomena noted were in part related to the formation of iron hydroxides and sulphuric acid. This reacts with the calcite to form gypsum, which has a lower density than the original pyrite and calcite. The XRD indicated that the iron hydroxides observed on the discontinuities are dominantly limmonite. Examination of the SEM and EDS suggested an increase in porosity, even at some distance from the macroscopic fissures.