548 research outputs found
Soil Reinforcement by Rigid Inclusions: Contamination of an Oil Storage Tank
An oil storage tank at the North suburb La Goulette (Tunisia) was founded on reinforced soft soil by floating sand columns of 6 m in length and 11% of improvement area ratio within a thick compressible clayey soil. Serious contamination of tank due to very significant differential settlement forces the decision to terminate its operations. Reinforcement by inclined rigid inclusions was suggested to neutralize the evolution of consolidation settlement in sub compressible clay layers. Numerical predictions were implemented for the study of the post behavior of tank on reinforced soil by rigid inclusions. Effectiveness of solution using inclined rigid inclusions is illustrated and, then, discussed. Modeling of the contact between the rigid inclusions, by means of element of interfaces, and soft clay has been seen of great importance when predicting the evolution of long term settlement
Educating Students Through Understanding the Pathology of Geotechnical Projects
Three projects of end of studies which are related to soil mechanics pathology case histories were undertaken by students at civil engineering department of National Engineering School of Tunis. The two first projects dealt with Joumine and Sidi SaĂąd earth dams cases. For Joumine dam, concrete slabs of the spillway have been affected by serious disorders. The first disorder is related to the swelling nature of soil foundation of concrete slabs. The second disorder is attributed to high excess pore pressure responsible of slabs up risings. As solution the jet grouting technique was designed to eliminate high pore pressure in the soil foundation of slabs. For Sidi SaĂąd dam disorders were attributed to high active soil pressures exerted on retaining walls of the spillway. As solution anchored cables were adopted to improve the stability of concrete walls. The third project dealt with four engineering structures crossing Tunis La Goulette express route. All approach slabs were affected by differential settlements due to the existence of highly compressible thick soft clay layers. As solution three soil improvement techniques (rigid inclusions, stone columns prefabricated vertical drains) were compared to stop non admissible consolidation settlements. For each case history, the methodology to diagnose causes of disorders is first presented, second, the utilized approaches, especially those involving finite element codes usage, are highlighted, finally proposal of remedies to re establish suitable exploitation of projects are exposed. This paper well illustrates the great importance for under graduated students, when preparing their works of end of projects, to more understand fundamentals in soil mechanics in parallel with treating serious problems of pathology of case histories
Comparison Between Stone Columns and Vertical Geodrains with Preloading Embankment Techniques
In the framework of âRadĂšs-La Gouletteâbridge project (Tunisia), this study focuses on the construction of embankments located in north Lake of Tunis. These embankments with averaged height of about 6 m are founded on highly compressible clayey sand and muddy sand layers. A soil improvement technique is then imposed, to overcome the lack of low bearing capacity and high pronounced settlements. Two solutions of soil improvement have been studied; the first one consists in vertical âGeodrainsâ drilled until 10 m depth associated with step by step construction of preloading embankment. The second technique is stone columns reinforcement up to 10 m depth. It is focused at estimation of bearing capacity and prediction of settlement of reinforced soil by handling the recent elaborated software programme âColumnsâ. The evolution of consolidation settlement of embankments as a function of time is also considered. The consolidation of improved soil is studied by using the âporoelasticâ prediction model and the Barronâs theory. A comparison between the two soil improvement techniques from the technical and economical viewpoints is presented. Compared to the âGeodrainsâ technique, the reinforcement by stone columns including the execution of embankments approximately leads to a gain of eight months and slightly cost reduced
Bearing capacity of a foundation resting on a soil improved by a group of columns
A new design method for a foundation on a soil reinforced by columns is described. A lower bound of the bearing capacity is determined within the framework of the yield design theory. It takes into account the three-dimensional nature of the problem and is applicable to a wide range of geometries. A parametric study on the improvement of the bearing capacity as a function of the proportion of reinforcement, and on the strength characteristics, is presented. A complete analytical solution is given for the strength of a composite cell subjected to a triaxial loading, which provides an insight into the reinforcement mechanism
Self-Adaptive Communication for Collaborative Mobile Entities in ERCMS
International audienceAdaptation of communication is required for maintaining the connectivity and the quality of communication in group-wide collaborative activities. This becomes challenging to handle when considering mobile entities in a wireless environment, requiring responsiveness and availability of the communication system. We address these challenges in the context of the ROSACE project where mobile ground and flying robots have to collaborate with each other and with remote human and artificial actors to save and rescue in case of disasters such as forest fires. This paper aims to expose a communication component architecture allowing to manage a cooperative adaptation which is aware of the activity and resource context into pervasive environment. This allows to provide the appropriate adaptation of the activity in response to evolutions of the activity requirements and the changes in relation with the communication resource constraints. In this paper, we present a simulation of a ROSACE use case. The results show how ROSACE entities collaborate to maintain the connectivity and to enhance the quality of communications
Bearing capacity of a foundation resting on a soil improved by a group of columns
A new design method for a foundation on a soil reinforced by columns is described. A lower bound of the bearing capacity is determined within the framework of the yield design theory. It takes into account the three-dimensional nature of the problem and is applicable to a wide range of geometries. A parametric study on the improvement of the bearing capacity as a function of the proportion of reinforcement, and on the strength characteristics, is presented. A complete analytical solution is given for the strength of a composite cell subjected to a triaxial loading, which provides an insight into the reinforcement mechanism
Effects of a Four-Week Small-Sided Game and Repeated Sprint Ability Training during and after Ramadan on Aerobic and Anaerobic Capacities in Senior Basketball Players
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Dermaseptins and Magainins: Antimicrobial Peptides from Frogs' SkinâNew Sources for a Promising Spermicides MicrobicidesâA Mini Review
Sexually transmitted infections (STIs) and human immunodeficiency virus (HIV), the causative agents of acquired immunodeficiency syndrome (AIDS), are two great concerns in the reproductive health of women. Thus, the challenge is to find products with a double activity, on the one hand having antimicrobial/antiviral properties with a role in the reduction of STI, and on the other hand having spermicidal action to be used as a contraceptive. In the absence of an effective microbicide along with the disadvantages of the most commonly used spermicidal contraceptive worldwide, nonoxynol-9, new emphasis has been focused on the development of more potential intravaginal microbicidal agents. Topical microbicides spermicides would ideally provide a female-controlled method of self-protection against HIV as well as preventing pregnancies. Nonoxynol-9, the only recommended microbicide spermicide, damages cervicovaginal epithelium because of its membrane-disruptive properties. Clearly, there is an urgent need to identify new compounds with dual potential microbicidal properties; antimicrobial peptides should be candidates for such investigations. Dermaseptins and magainins are two classes of cationic, amphipathic α-helical peptides that have been identified in the skin extracts of frogs Phyllomedusa sauvagei and Xenopus laevis. Regarding their contraceptive activities and their effect against various STI-causing pathogens, we believe that these two peptides are appropriate candidates in the evaluation of newer and safer microbicides spermicides in the future
Conception des fondations superficielles reposant sur des sols granulaires en utilisant la vitesse des ondes de cisaillement
Un bon dimensionnement dâune fondation superficielle nĂ©cessite une bonne
caractérisation du sol sur lequel elle reposera. Pour le cas des sols granulaires, les
essais de reconnaissances destructifs (SPT, CPT, etc.) impliquent la conversion des
profils obtenus du sol exploré en un profil de rigidité afin de pouvoir estimer sa
portance. Une telle tĂąche peut induire des erreurs au niveau de lâestimation Ă©tant donnĂ©
quâelle nĂ©cessite le passage dâun nombre de paramĂštres (N, qc) nâillustrant pas lâĂ©tat rĂ©el
du sol (rigidité) à des paramÚtres caractérisant sa performance (module élastique,
coefficient de Poisson). La caractérisation des sols granulaires en utilisant la vitesse des
ondes de cisaillement (non destructive) nous permet de contourner ce problĂšme Ă©tant
donnĂ© quâelle nous donne directement la variation dâun paramĂštre intrinsĂšque au sol (Vs)
Ă partir duquel il est possible dâeffectuer le dimensionnement. La disponibilitĂ© dâune
technique de mesure de vitesses de cisaillement (P-RAT) sur des Ă©chantillons de sols au
laboratoire gĂ©otechnique de lâUdeS, nous a permis de mettre en Ćuvre lâapplication de
Vs dans lâestimation de la portance des sols granulaires.
Au cours de ce mémoire, une procédure servant à estimer le tassement des fondations
superficielles reposant sur des dépÎts granulaires est présenté. Les paramÚtres de
cisaillement (Vs, G) dâun sable dĂ©terminĂ©s Ă lâaide des essais de caractĂ©risation (P-RAT)
ont été utilisés pour construire un modÚle numérique de fondation. La consistance des
résultats numériques du modÚle a été confirmée à travers des essais de chargement de
plaque. Ce travail montre donc lâimportance des paramĂštres de cisaillement dans la
modĂ©lisation dâune application frĂ©quente en gĂ©otechnique. Il constitue un dĂ©part
considérable pour la construction de relations constitutives basées sur le paramÚtre
vitesse de cisaillement
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