Sur la représentation graphique de la fracturation des sondages carottés en terrain rocheux

Using the rock cores obtained from the preliminary borings performed on two dam sites, the author made a statistical study of the spacing of discontinuities as observed along the cores. For that purpose, he used cumulative curves to represent populations of core piece lengths. He was led to improve the common use of the method, which does not provide much information about the lengths of broken core pieces (except their total percentage). The method may be applied with better results not on the whole core, but on the one hand, to the lengths of unbroken core and on the other hand, to lengths of broken core, thereby yielding statistical information about both discontinuity spacings and lengths of broken core.     

Etude d'une methode d'evaluation globale des precurseurs de la reaction haloforme

The aim of this survey is to devise an over-all method for evaluating haloform reaction precursors. The principle of the analysis is based on the action of iodine on the precursors and on the measurement of the amount of iodoform obtained, by spectrophotometry in the ultra-violet band. The reaction parameters (conditions of pH and of extraction, time of reaction) were studied and thus allowed us to establish a simple analytical method of operating, presenting both precision and sensitivity.Iodine constitutes an interesting reactive for this measurement because on the one hand it is not consumed by ammonia and on the other the iodoform presents four characteristic bands in UV. The reaction gives good results with ketonic precursors whereas with metapolyhydroxybenzenes these are inferior to those obtained by chlorination.     

Traitement experimental d'epuration d'une eau de surface par lagunage: Aspects chimiques et microbiologiques

Polluted river water was treated by lagooning in an experimental bed. The evolution of the most representative parameters of the organic and bacterial pollution has been studied in relation to the period of retention. The predominant bacterial populations have been identified and their qualitative and quantitative variations have been related to the degree of pollution. The analytical results are commented upon the advantages of the method are stressed.     

Apport d'une approche probabiliste de la stabilité pour la conception des talus de mine a ciel ouvert. Applciation à la mine de Carmaux,france

Slope stability problem in operacast mines is one that is often encountered by geotechnical engineers in the design of slopes in jointed rock masses. To resolve this problem, several elements such as the geometrical and the geotechnical parameters of the fracture set of the rock mass have to be considered. In this paper, the characterization of the statistical distribution of geometrical fracture parameters enable the simulation of the rock massive and thus provides a realistic approach to the analysis of failure mechanisms that may affect the rock mass. Computer programs were developed and applied to the opencast coal mine of Carmaux (France). Test results led to the proposal of different slope angles and bench widths for different slope orientations in the mine.     

Utilisation des sondes TDR pour estimer la masse de soluté retenu par une couche d'argile lors d'une infiltration

Résumé. Un essai de longue durée est réalisé sur un matériau d'étanchéité, l'argile du Gault. Par une infiltration continue du lixiviat de scories, sous une charge hydraulique constante de 98,5 cm, nous avons suivi la variation spatio-temporelle de l'humidité θ (z, t) et de la conductivité électrique σ (z, t) dans une colonne du sol. La relation entre la teneur en eau volumique (θ) et la constante diélectrique (ε) du sol est établie en utilisant la méthode TDR. Nous avons également établi une relation entre la fraction soluble de la solution et sa conductivité électrique. Cette relation permet de suivre la distribution spatio-temporelle du soluté dans la couche de sol. Plusieurs chercheurs ont montré qu'il est possible de tracer les courbes d'élution d'un traceur non réactif en utilisant la méthode TDR. Cette méthode permet alors d'éviter l'utilisation des bougies poreuses d'extraction des solutions du sol et les analyses chimiques co?teuses de l'éluant. Les résultats des essais d'infiltration effectués sur la couche d'argile montrent que la conductivité électrique mesurée à l'aide des sondes TDR sert à localiser la fraction soluble dans la colonne. Le coefficient de dispersion calculé est resté constant au cours du temps autour d'une valeur moyenne de 1,5×10^–10 m²/s. Ce qui montre que le coefficient de dispersion n'est pas très influencé par le sol et par son degré de saturation. Electronic Publication     

La microfaune des boues activees. Etude d'une methode d'observation et application au suivi d'un pilote en phase de demarrage

The microfauna of activated sludge is well known as a potential indicator for operational control of biological treatment systems. An experiment was carried out during start up of an industrial scale pilot plant which was led with municipal sewage. Density of microfauna was evaluated using a counting chamber technique, and the results correlated with physicochemical factors. It was found that: the counting chamber technique is quite reliable provided the investigated volume reaches 10 mm³; grouping of microfauna by trophic characteristics makes the observation easier for the non-specialists without loosing too much information: and the evolution of microfauna is determined by a set of parameters for which epuration yield does not play a major role.     

Traitement des effluents urbains ou industriels par entrainement des polluants a l'occasion d'une precipitation de CaCO3

Studies carried out in our laboratories on calcium carbonate precipitations have led to the conclusion than substantial amounts of organic matter could be entrained by the crystals that are produced and in particular when the precipitate is in the form of vaterite. Moreover entrainments of this type are used currently in sugar-refining for the purification of sugar juices. Such CaCO₃ precipitation may be easily induced by means of the reaction of lime with a current of CO₂-enriched gas which is bubbled through the solution. Given also the well-known coagulating properties of lime, it has been considered worthwhile investigating the treatment of certain wastes by means of this method. The initial trials were sufficiently conclusive for the SOAF Company to taken an interest in the project and for a decision to be made to construct a pilot plant of 10 cm h⁻¹ capacity. Concurrently with this, a 301 h⁻¹ laboratory unit was also built, and it is this which has provided the initial results that we propose to set out here.     

Combinaison d'une cellule d'extraction liquide-liquide en continu et d'un couplage CG-SM en vue de l'analyse des pesticides dans les eaux

The occurrence of synthetic organic chemicals in drinking water supplies has prompted the European Economic Community to establish standards for pesticides. Currently, the limit on total pesticides is 500 ng l⁻¹ with no individual pesticide to exceed 100 ng l⁻¹. The variability of pesticides, both in concentration and composition, indicates that composite rather than grab samples are desirable for analysis of the water quality. Furthermore, the variability in composition makes a broad spectrum analysis preferable to individual compound analysis so that many compounds can be analysed simultaneously.Although composite broad spectrum samples are desirable from a collection point of view, the occurrence of many pesticides in one sample presents a problem for individual compound quantification and identification. For this reason, gas chromatography (GC) is used to separate the compounds and mass spectrometry (MS) is used to identify and quantify the compounds. Coupled GS-MS avoids interferences which may occur in GC by using a separate method (other than retention time or volume) to identify compounds.This research compared liquid-liquid extraction (LLE) in the batch and continuous mode. The LLE process is accomplished in a continuous mode by mixing the water and solvent in a coil, allowing the water and solvent to separate in a quiescent decantation cell, then recirculating the solvent by a separate distillation cell while the water goes to waste. Tap water was spiked with pesticides at 10, 50 and 100 ng l⁻¹. Extraction efficiency was compared at each of the three spiking concentrations. The extracts were analysed on GC-MS using a moving needle injection technique to enhance sensitivity. The identification and quantification of compounds were accomplished by MS using the fragmentometry technique which enhance sensitivity of the analysis.The results indicate that continuous LLE will recover an average of 75% (± 14%) of the pesticides in the 10–100 ng l⁻¹ range recoverable by batch LLE. There was no significant difference in recovery for structurally different pesticides (chlorinated, nitrogenous or phosphoric) as all fell in the 75 ± 14% range. Eighteen pesticides were identified and quantified by the GC-MS in a 25 min analysis.This demonstrates that the continuous LLE technique can be used to automate collection of composite samples if the reduction in extraction efficiency is taken into account. The continuous LLE can handle much larger volumes of water than the batch LLE. Composite samples can be continuously collected over time, a sampling regime not possible with batch LLE. This technique when coupled with GC-MS can be used to identify and quantify pesticides at the ng l⁻¹ level and can be applied routinely for analysis of pesticides at approximately the same price as individual pesticides analysis.     

Conception et réalisation d'une base de données géologiques et géotechniques orientée vers la cartographie géotechnique: Application a la ville de Tunis (Tunisie)

The concept and implementation of a geological and geotechnological data base system is presented. The various systems data and parameters are defined and organized in separate files. An example of the application of this data base system is given using data gathered for the city of Tunis.