Utilisation de la photographie de moire pour mesurer l'usure des granulats dans les couches superficielles de chaussees

The author describes a rapid and non-destructive method of following and measuring the evolution of the shape of aggregates used in wearing courses of roads. The method is based on the moiré phenomenon which, in the present example, allows us to draw graphic curves, with a precision up to a few tenths of millimeters on a vertical cut. The article describes:

- the method and equipment necessary to obtain a workable moiré on a photograph,

- a computer-programmed chain which, during a series of topographical cross-cuts, measures and studies the distribution of spacings of contour lines. The spacings vary according to the rounded nature of the aggregates which are classified according to their shape.

The road studied is then characterized by drawing graphs of the distribution of the lengths of cuts of the road, occupied by the different shapes of the selected aggregates. The author gives a few examples of the uses of the method in studying the evolution of surface dressings and embedded stone on concrete. The author also shows that his method can be used in other fields than civil engineering.     

Determination des caracteristiques mecaniques des graves non traitees au triaxial a chargements repetes

Untreated gravels study was marked a long time by an empiricism mainly based on the global behaviour of these materials in pavements. For that reason, specifications in use may seem sometimes restrictive and lead to reject new and cheap materials. Repeated loading triaxial test chiefly developed for the last twenty years in Anglo-Saxon countries allows to solicit sample with stresses levels comparable to those induced by trafic in pavements. The paper presented describes an apparatus designed in the “Laboratoires des Ponts et Chaussées” network and meant more particularly to usual studies. The main relations between untreated gravels stresses and deformations (reversible and permanent) will be reminded. This new test method, very discriminant, allows to compare easily materials between themselves. The paper gives, by way of illustrations, examples:

- Behaviour of untreated gravels coming from crushed stones and alluvial untreated gravels corrected by fillerised sands.

- Attrition study for untreated gravels elaborated from aggregates having a high Los Angeles coefficient.

     

Classification des granulats pour les couches de roulement des chaussees

Resistance to polishing mainly depends on microroughness of stone elements, which is considered more or less as a natural quality of the rock and is in connection with its mineralogical composition. On the contrary mechanical resistance depends also on exploitation methods and on the technology of production. We must point out that the knowledge of resistance to polishing of aggregates can be improved if more precise relations between laboratory tests, real behaviour in road courses under the traffic and the proposed classification can be found. This classification depends on two laboratory tests: polished stone value and Los Angeles.     

Determination de la permeabilite des alluvions a partir de la prospection electrique

Bulletin of Engineering Geology and the Environment - Les nombreuses reconnaissances par sondages électriques, réalisées lors de ces vingt dernières années, en vue...     

Importance de la petrographie dans l'approche des mecanismes de la reaction alcali-granulat

Résumé Dans les bétons, les granulats subissent une agression liée à l'hyperbasicité du milieu. Cette agression connue sous le nom de réaction alcali-granulat peut être limitée ou au contraire se développer jusqu'à la ruine des ouvrages. L'évolution de la réaction dépend de plusieurs facteurs: la nature pétrographique, l'accessibilité, des minéraux, aux solutions agressives et surtout l'état d'altération préexistant de la roche. Ces deux derniers paramètres pouvant être approchés par les mesures de surfaces spécifiques et visualisés par les observations pétrographiques en microscopie optique et électronique. Nous présentons des exemples montrant le développement de la réaction et son évolution suivant la nature pétrographique et le degré d'altération des granulats utilisés.

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Importance of the petrographic analysis for approaching the mechanisms of alkali-aggregate reaction

Aggregates used in concrete are sub mitted to an etching due to the hyperbasic medium. This chemical reaction is known as the alkali aggregate reaction and can be either limited or sometimes so well developed that it lead to the ruin of the whole structure. The evolution of the reaction depends on several factors: the petrographic characteristics, the penetration of aggressive solutions into the aggregates and above all the state of alteration of the original rock. The two last mentioned parameters can be approached by means of specific area measurements and visualized by petrographic analysis in optical and electronical microscopy. The examples presented in the paper point out the development of the reaction and the evolution of the phenomenon un function of the petrographic properties and of the state of alteration of the aggregates used.

     

Etude de l'evolution de la qualite des eaux de riviere

In France, the creation of a “Ministère de l'Environnement et du Cadre de Vie” and “Agences Financieres de Bassin” has made it possible to obtain information on the water quality of rivers and on the measures necessary to improve water quality. Particularly in the Adour-Garonne Basin, much information is now available. The methodology needed to draw conclusions concerning the quality of the rivers and to show the effectiveness of control measures has been developed.This method has been tested in two catchments (Fig. 1): L'Adour (15,000 km²) and La Dordogne (24,000 km²). The steps that were necessary before this method could be used were: critical assessment of the available data; identification and measurements of pollution sources. This called for the collection of information, annual statistics for each sampling station and information concerning the value and importance of measured parameters.Detailed information is available from 1971 and 1976 and this is shown by maps and graphical representations of the variations in the value of different parameters (Fig. 2).Statistical analysis has also been carried out on the information available for the period 1971–1976.Two methods were used: analysis of the principal components, the method most used being shown by Figs 3 and 4 and the “STATIS” method developed recently which treats the whole data “At 3 indices” (Fig. 5).Research has been carried out on the causal relations between the water quality and the sources of pollution.A simple graphical method is proposed to explain the effect of a strongly preponderant pollutant source. It allows easy visualisation of the change in the relationship between two series of variables (Fig. 8).In general cases of several sources of pollution a simplified method using BOD exclusively has been developed. It consists in comparing the values measured in the river and the estimates obtained from inflows of various sources and those from upstream basins (Fig. 9).The application of this method has made it possible to distinguish local or general tendencies in reference to the intervention realised by the “Agence Financiere de Bassin”.Attention has been given to the variations obtained between laboratories and research information and the necessity to extend application of the statistical method to parameters other than BOD₅.Comparable action is being taken for the whole basin of the Rhone (French). The information obtained for “L'Adour and La Dordogne” has led to a study not only of the concentration of pollutants but two types of flow, with flow measurements and concentration being taken into account in order to eliminate hydraulic effects.     

Materiaux pierreux non traditionnels dans la construction des routes

It is already many years that the lack of aggregates for building is deeply felt in the plain zones. This phenomenon hits both the building section, in which aggregates are mostly used in reinforced concrete, and mainly the road section where, as known, the use of lapidary material is enormous and, for the moment, non substituted not only in each single layer part of the pavement road structure but also in all the many works completing it. It is therefore evident the remarkable interest for a research tending to find non traditional aggregates with bad characteristics that, however, can compose accettables mixtures for parts of the pavement road structure.     

Mesurein situ de la permeabilite des Argiles

Bulletin of Engineering Geology and the Environment - La méthode usuelle de mesure de la perméabilité des dépôts argileuxin situ (essai à charge variable en...     

La porosite des granulats de laves basaltiques de la Reunion

Basaltic lava from the Reunion are characterised by a high closed porosity. Water can only penetrate open voids on the surface. When the density increases, water content also increases. In fresh concrete, aggregates attract and gradually retain water during the setting process of the cement; this greatly modifies the workability and the strength of concrete. Results of the measurement of water content of sands and stones versus time are exposed.     

Prevision de la teneur en fines des sables de concassage

The percentage of fines in the crushed sand is one of the important data that has to be taken into account carrying out the study of the rocks in a quarry. It is taken for granted that the sand fines percentage is a function ot the petrographic structure, of the grains size, and of the rock cement quality, and, in part, of the crushing method. This study brings up a few results obtained from different rocks which have gone through a fragmentation's test Los Angeles, and have been observed for a petrographic identification. This study shows that, by the association of those two methods it is possible to estimate the percentage of fines in the crushed sand through the examination of rock samples.     

Influence de la taille des mottes et du mode de compactage sur la perméabilité des sols

In the domain of impervious barriers, many factors influence the permeability of compacted soil layers. These factors can lead to discrepancy between the permeability results in the laboratory andin situ. In this context, a laboratory study showed the influence of the size of clods and the method of compaction on permeability of highly plastic marl, compacted dynamically with standard Proctor energy and statically at different stresses, under the same conditions of water content and dry density. This paper also presents the results of a comparative study which has been conducted on the influence of the method of compaction on the permeability of the marl and that of a low plastic silt.     

Toxicite des eaux de ruissellement de la fonte de neige en milieu urbain

There is a current paucity of information on the characteristics of water originating from melting snow in urbanized areas. In fact no data exist on the potential chronic toxicity of waters originating from melting snow combined with sewage waters of industrial and domestic activities. Bioassays were conducted on the green alga Selenastrum capricornutum to evaluate the composite effect of all pollutants occurring in waters originated from melting snow in urbanized areas and also to determine the long-term bioavailability of selected toxicants in these waters.The publication resumes a sampling study of two outfalls (Curotte-Papineau and Meilleur-Atlantique) from collector systems on the island of Montréal, Québec, Canada (see Fig. 1). Both sewer systems are of the combined surface runoff-wastewater type, are self contained and drain watersheds of 11.7 and 22.2 km² area respectively (see Table 1). The sampling program carried out in spring (March–May) 1978, was oriented towards the analysis of flow-quality relationships during two dry and three snowmelt periods. The flow from the intrusion of snowmelt into the sewage networks were due not only to high air temperature and solar radiation conditions but also to a heavy rainfall (9.67 mm; maximum intensity of 4.6 mm h⁻¹. The principal water quality parameters studied were BOD₅, COD, Cl⁻, N_in, P_i, Pb, Cr, Zn, Cn⁻ and SS (see Table 2).In addition a bioassay based on the fertility potential [the Selenastrum capricornutum Printz algal assay bottle test; U.S.E.P.A. (1978)] on filtered samples (1.2 μm GF/C) of waste water was used to detect any toxological qualities of the outfalls during both dry and snowmelt periods. An analysis of the relationship between chemical quality and the toxological properties of the samples from both sewage networks showed that water collected during a period of snowmelt without rain had a greater potential chronic toxicity and greater mean ratios of B_EDTA/B than combined water collected during a dry climatic period (see Table 3). This toxicity is due mainly to inorganic compounds. However, the increase in water discharge rate during periods of snowmelt accompanied by rain results in an apparent dilution of the aquatic toxicants. The potential chronic toxicity of water during the latter periods is consequently reduced compared with combined waters during dry periods.Knowledge of relationships between water flow and the chronic toxicity characteristics of waste water from urban snowmelt is necessary in the planning of any future combined water treatment system.     

Contribution à l’analyse des mouvements gravitaires rapides de grande ampleur par la comparaison des materiaux sources et des dépôts: exemples alpins

Source areas and deposits of the La Madeleine rockslide-avalanche were analysed to quantify particle-size reduction with transport. Block volumes of the source area are simulated using geometrical programs based on stereological data. Grain volumes of the deposits are estimated by image analysis and granulometric tests. Comparison of the blokometric and granulometric curves reveal preservation of larger blocks and production of fine grains as matrix. Field observations confirm these results with larger blocks at the top of the deposits, and dynamic disintegration processes fixed in the deposits. Similar structures are discernable in the Flims and Köfels rockslide deposits. The La Madeleine, Flims and Köfels rock masses are initiated by sliding along pre-existing planes as bedding or foliation. Shearing and dilatancy processes take place along these planes to produce shear band gouge as faults. Shear stresses affect rock slabs by fracturing during displacement, to a granular state in the deposits. Original structures are preserved by confinement forces and topographic controls. At this stage, the granular rock mass cannot just slide, but evolves progressively to a fluid-behavior motion. Angular grains heterogeneous in size, confinement processes and larger blocks at the top of the rock mass are opposed to mixing, preserving original structures. Dynamic disintegration continues during the rock-avalanche stage by punching, grain extraction around larger blocks or collision phenomena. Mobility of high-speed rock movements results from topographic control and dynamic disintegration processes. At La Madeleine, Flims and Köfels, the rock mass impacts the opposite slope of the U-shaped valley, consuming energy. At La Madeleine, dynamic disintegration took place before impact, and the rock mass was able to flow along the axis of the Arc River valley. At Flims, dynamic disintegration of the rock mass was intensive, but not enough to completely evolve to a rock-avalanche. Lateral domains flowed along the axis of the Rhine River valley due to the lack of confinement. At Köfels, gneissic rocks were too hard to produce enough fine grains during the sliding stage, and the rock mass was stopped by topographic impact. These observations suggest that dynamic disintegration is a fundamental process in understanding the mobility of these large rock masses. Production of the matrix explains the transformation of the sliding block to a rock-avalanche, at the origin of its long travel distance. Modeling needs to take into account the dynamic disintegration that modifies the mode of transport as the source of mobility.     

Intérêt de la minéralogie des granulats dans la connaissance des risques de l'alcali-réaction

Résumé. Dans les ouvrages en béton apparaissent parfois des désordres sous forme d'un réseau de fissures multidirectionnelles dont le nombre et l'épaisseur s'accroissent au cours du temps. La cause en est une réaction chimique entre la silice des granulats partiellement dissoute et les alcalins du ciment contenus dans la solution interstitielle à pH très élevé, réaction génératrice d'un gel souvent expansif. Les irrégularités que présentent les structures du quartz, de la calcédoine et de l'opale favorisent l'introduction d'eau et d'ions divers qui joueront un r?le essentiel dans la mise en solution de la silice.La fragmentation tectonique de grands cristaux de quartz en une multitude de petits cristallites augmente les surfaces de contact quartz/solution interstitielle, donc les risques de réaction alcaline. La prévention des alcali-réactions passe par une connaissance des éléments minéralogiques et pétrographiques qui constituent les granulats. L'emploi du microscope polarisant et du compteur de points permet une bonne approche du pourcentage de minéraux réactifs; des tests de qualification (test dimensionnel, test cinétique...) conforteront le diagnostic. On distinguera alors trois classes de granulats, non réactifs (NR), potentiellement réactifs (PR) et potentiellement réactifs à effet de pessimum (PRP). Un exemple d'application est donné pour le bassin de la Garonne sur la relation entre l'évolution de la composition minéralogique des alluvions du fleuve en fonction de l'apport des affluents successifs et leur degré de réactivité. Electronic Publication     

Recherches sur les risques pouvant resulter de la pollution chimique des eaux d'alimentation—II. Etudes comparatives de la toxicite a long terme et de la cytotoxicite des micropolluants organiques extraits des eaux utilisees pour la preparation des eaux d'alimentation

Micropollutants extracted by chloroform from raw river waters used for preparation of drinking waters have been divided into two categories pending the degree of cytotoxicity shown by another team of research using a given cellular system: fractions with high cytotoxicity and fractions with low cytotoxicity.In parallel groups of 50 rats and 60 mice, half male and female, were fed, from weaning, diets containing those fractions.Comparison of the results showed a correlation between the two types of results, only in the case of some biochemical parameters.In regard to the long term effects (lesions of the liver, increase in the incidence of malignant tumors in treated animals), no correlation could be found.

Résumé

Des micropolluants organiques préparés par extraction chloroformique d'eaux brutes ont été répartis en 2 catégories, en fonction des résultats obtenus dans les investigations d'une autre équipe de chercheurs sur un systéme cellulaire: fractions à cytotoxicité forte et fractions à cytotocixité faible.Parallélement, des groupes de 50 rats et de 60 souris, par moitié mâles et femelles, ont reçu dans leur régime, à partir du sevrage et pendant pratiquement toute leur vie, les deux catégories de micropolluants.La comparaison des résultats obtenus dans les 2 types d'investigations nà révélé de corrélation que dans le cas de certains paramétres biochimiques et encore seulement dans une certaine mesure. En ce qui concerne les effets à long terme observés chez les lots traités des 2 espéces animales soumises aux épreuves (nettes altérations hépatique, augmentation de l'incidence des tumeurs malignes), aucune corrélation n'a pu être établie entre les critéres toxicologiques retenus et le degré de cytotoxicité des micropolluants sur le système cellulaire utilisé.     

Permeabilitein situ des argiles superficielles de la mer champlain

Bulletin of Engineering Geology and the Environment - Les paramètres hydrauliques de la couche superficielle d'argile fissurée et altérée qui recouvre l'argile de la mer...