| Environnement, ingénierie & développement |  |
N°80 - N°Spécial bis, Congrès Sites et Sols, juillet 2019
1. Éditorial n°80 spécial Congrès Sites et Sols, Déchets Sciences et Techniques
Comme nous l’annoncions dans l’éditorial du précédent numéro (n°79), le numéro 80 de DST est également un numéro spécial, consacré comme le précédent aux deuxièmes Rencontres Scientifiques sur la Réhabilitation et la Valorisation des Sites et des Sols pollués (RV2S-2018).Le numéro 80 regroupe six articles, issus de ce congrès, qui viennent compléter le champ scientifique et technique couvert par les 7 articles du précédent numéro.L’éditorial du n°79 a déjà décrit le séminaire RV2S-2018 qui s’est tenu à l’École Nationale d’Ingénieurs de Saint-Etienne (ENISE) les 29 au 30 octobre 2018. Le n°80 devra donc se contenter d’un éditorial plus succinct, inutile de remplir ces lignes d’informations déjà données.Notons cependant que ce numéro 80 est doublement spécial !Spécial car consacré à des communications orales sélectionnées d’un congrès scientifique comme annoncé ci-dessus.Spécial également parce qu’il renferme l’unique article jamais publié en langue anglaise dans DST : « Analysis of differential heaving distress in the structure due to degradation of founding soils » par Rajesh Kumar, auteur indien non francophone.Certains salueront cette initiative comme le gage d’une ouverture internationale de la revue. D’autres pourront s’en inquiéter comme d’un signe de l’érosion de la francophonie au profit de l’anglais scientifique. Il ne s’agit pourtant rien de cela. DST maintient sa ligne éditoriale […]
2. Vieillissement d’une mousse à base de tensioactif dans un sol sableux-argileux modèle
Lubricants are used in the excavation procedure by earth pressure tunneling machines (EPBs). They help to fluidize the soil structure and thus prevent the clay from sticking to the cutting head. Excavated soil is classified as waste and stored in the disposal area. Reuse of this type of soil depends on their state after excavation and their evolution over time. To identify and understand the physical and mechanical evolution of excavated soil, a first step is to analyze physical evolution of foam on the soil. The foaming agents are characterized by aging which results in a physical modification of the foam. The aim of this study is to analyze the aging of CLB F5TM surfactant based liquid foam mixed with clayey sandy soil. The evolution of the volume of the foam over time shows a rapid degradation of the bubbles that constitute it. The physical degradation of the foam in the soil takes more time compared to the foam in the open cell thanks to the protection of bubbles by porous media. A column drainage test was performed to identify the evolution of the foam in the mixture through its effect on interstitial pressure. These tests show that the presence of the foam in the mixture promotes the drainage phenomenon compared to the case of unconditioned soil.
3. Retour d’expérience sur les techniques de traitement en nappe et présentation de solutions innovantes
In situ remediation techniques for groundwater pollution are quite diverse. However, the success of these is often random. The first part of the article will focus, from a literature review and some examples, to determine the parameters that unfortunately lead to a low efficacy of treatment. This point will be supplemented by an analysis of the feedback on treatments at the pilot scale. The limits are generally related to the heterogeneity of the geological formations but also to a poor targeting of the laboratory analyses or to a poor monitoring of the rehabilitation. In a second part we will examine recent progress to maximize the effectiveness of in situ treatments. At first, we emphasize diagnostic techniques that make it possible to target the flow of pollutants. Following a general presentation of innovative techniques, we will particularly present an original technique : the injection of foam to block the porosity of around a source area.
4. Analysis of differential heaving distress in soil-structure interactions due to degradation of founding soil by chemical contaminations
In the process of rapid industrialization, land degradation is being observed in presence of chemical or other alterations in the natural soil. Expansive soil resulting from penetration of liquor in to the ground creating differential heaving stress in the foundation of the structures. Present paper deals a case study of distressed structure founding on the soil which is being contaminated with caustic liquor resulting from the process of manufacturing of Alumina. A reinforced cement tertiary thickener structure of Alumina plant (in India) rests on concentric columns got distress features in the form of upheaval of footings after four year of commissioning. The concrete and soil in the foundation area got contaminated with caustic liquor resulting in to the expansion of materials near to the foundation and creating differential heaving distress in the foundation and columns. This paper also deals the remedial measures and a methodology to make the structure stable and durable.
5. Conditions aux limites pour le modèle du drainage de sables en une et deux dimensions
The study of soil pollution and treatment need a good knowledge of hydrodynamic properties. Therefore, models and drainage experiences are commonly used. In order to valid the models, boundary conditions are required. Drainage modelling in sand has been performed and compared with experimental results obtained in one-dimension column (1D) and in two-dimension pilot (2D). Comparison was established by testing different boundary conditions at the device outlet and by using concordance indicators. The studied experimental results are : outlet flow, cumulated volume at the pilot outlet, hydraulic load values and saturation at different levels of the pilot. Experiments indicate that a Neumann condition at the outlet is more suitable than a Dirichlet constant pressure condition whether for 1D or 2D experiences.
6. Modélisation par éléments discrets de la compressibilité d’un sol sablo-argileux traité par une mousse en cours du temps
Lubricants are used to limit the tunneling shield's impact with the soil, also to facilitate the extraction of excavated soil. In this study, we are interested in the technique adopted by earth pressure tunneling machines (EPB) where surfactant foaming agents are used. Excavated soil is generally classified as waste and stored in the disposal area. The mastery of the physicochemical and mechanical evolution of these wastes makes it possible to explore methods of valorization.The aim of this study is to numerically model a granular medium using the Discret Element Method DEM method in order to study the compressibility of soil-foam mixtures during their evolution over time at the grain scale. The foaming agent is in the form of surfactant bubbles, thus constituting a second granular medium which mixed with that of the soil aggregates. The rigidities of the grains were deduced from the triaxial tests. The modeling is carried out for results oedometric tests. A difference of 14%between experimental and numerical values was founded. Furthermore, the model describes the reduction of the compressibility coefficient of the conditioned soil over time to find the coefficient of the unconditioned soil found experimentally.
7. Étude du séchage naturel des sédiments du port de Dunkerque en vue de valorisations ultérieures
Dredging operations play an essential role in the economy, the environment and the development of a region. These operations generate large volumes of sediments that become waste when they are land managed. These high water content sediments pose problem for its transport and its reuse or storage. From the environmental and economic perspective, natural drying is the best dewatering method. In order to optimize this technique, this present study explains how to determine dewatering ability criteria by the use of laboratory tests. For that, dewatering test is performed on harbor sediments of Port of Dunkirk. Results are discussed and undrained shear strength versus liquidity index relation is proposed.