APPLICABILITY OF SHANSEP METHOD IN EVALUATION OF PRECONSOLIDATION PRESSURE

This article presents an experimental study on 81 specimens made from three different mixtures of clay and sand. To ensure uniform initial parameters, all specimens were prepared with an initial water content of 30%. Two series of unconsolidated undrained shear tests under different overconsolidation ratios were conducted on a direct shear apparatus: the first aims to determine the SHANSEP (Stress History and Normalized Soil Engineering Properties) parameters namely S and m, whereas the second is used for evaluating the preconsolidation pressure. This work has provided an opportunity to investigate the influence of sand content on SHANSEP parameters and moreover to study the reliability of the preconsolidation stress estimated by the SHANSEP procedure

Parametric and Comparative Study of a Flexible Retaining Wall

This paper presents design of a self-stabilizing retaining diaphragm wall, using conventional analytical calculation method based on subgrade reaction coefficient and by numerical method with finite elements method FEM can lead to various uncertainties. Hence, engineers have to calibrate a computational strategy to minimize these uncertainties due to numerical modeling. For both two methods, this paper presents various simulations with the structure installed into the supported ground without surcharge. For the first method, the analysis has investigate the influence of main factors such as the wall rigidity, the different stages of excavation, the Young’s modulus, the cohesion and internal friction’s angle of the soil. For the FEM method, two constitutive soil models are used such as Mohr-Coulomb MC and hardening soil model HSM. In case of the last model HSM, the variation of required and additional factors for the model was investigated as well as secant modulus stiffness Eref50, unloading and reloading stiffness modulus Eur, power factor m and Over-consolidated ratio OCR. The results from of the various simulations carried out are confronted with other experimental and numerical results [4]. Avery good coherence results are showed

The Neuro-genetic approach for estimating the compression index

In the last decade, a number of empirical correlations have been proposed to connect the compression index to other soil parameters, such as liquid limit, plasticity index and the void index. This paper presents a correlation study between the physical properties and compression index which was conducted on normally consolidated clay by the hybridization of two approaches (artificial neuronal networks and genetic algorithms). A comparison was made between the measured experimentally and predictions compression indexes. The obtained results indicate that the Neuro-genetic model has the ability to accurately predict the compression index thus be used in practice by geotechnicians

The Neuro-genetic approach for estimating the compression index

In the last decade, a number of empirical correlations have been proposed to connect the compression index to other soil parameters, such as liquid limit, plasticity index and the void index. This paper presents a correlation study between the physical properties and compression index which was conducted on normally consolidated clay by the hybridization of two approaches (artificial neuronal networks and genetic algorithms). A comparison was made between the measured experimentally and predictions compression indexes. The obtained results indicate that the Neuro-genetic model has the ability to accurately predict the compression index thus be used in practice by geotechnicians

The Neuro-genetic approach for estimating the compression index

In the last decade, a number of empirical correlations have been proposed to connect the compression index to other soil parameters, such as liquid limit, plasticity index and the void index. This paper presents a correlation study between the physical properties and compression index which was conducted on normally consolidated clay by the hybridization of two approaches (artificial neuronal networks and genetic algorithms). A comparison was made between the measured experimentally and predictions compression indexes. The obtained results indicate that the Neuro-genetic model has the ability to accurately predict the compression index thus be used in practice by geotechnicians

Numerical modelling of infiltration profiles in the silt Tlemcen (Algeria)

It is obvious that for geotechnical knowledge of soil properties namely, suction-water content and water content hydraulic-conductivity relationship is essential to solve the problems associated with flow in unsaturated soils. The best way to evaluate these properties is to make direct measurements. However, the hydraulic-conductivity water content and suction-conductivity relationship are complex and it is often very difficult to measure for practical reasons, economic and spatial variability. Indeed, the used equipment is expensive and the tests are slow. Of more over the spatial variability of this property that makes the steps number necessary to characterize a site is relatively large. Furthermore, when this relationship is determined, usually it has only limited information and it is always desirable to extrapolate the experimental curve. Facing these difficulties, this given research targets computer tool to assess this relationship from other measurable parameters. In this paper, we used the software “flow line temperature” to achieve numerical and graphical simulations of the water flow in a soil initially unsaturated non-deformable modeling the evolution of the water content and suction in function of depth. The use of this software allowed us to make comparison with the experimental results [18] as well as a qualitative assessment of the drought penetrating in an unsaturated soil

Etude du transfert hydrique dans les sols non saturés : Echange sol-atmosphère

-Cette thèse étudie le transfert hydrique dans les sols non saturés et analyse sur la base des travaux antérieurs et en cours, l'effet de la sécheresse sur les constructions. Le mémoire comporte une synthèse bibliographique portant : - sur les généralités relatives aux transferts hydriques isothermes dans un milieu poreux à degré de saturations variable, sur les approches disponibles pour décrire ce phénomène qui est ramené physiquement à un processus décrit par une équation aux dérivées partielles de type parabolique, fortement non linéaire, - sur des solutions analytiques des écoulements à partir d'un puits à charge constante et à partir d'une source circulaire en surface à pression constante négative ou nulle, - sur l'analyse et la compréhension du système " mouvement de terrain différentiel consécutif à la sécheresse et à la réhydratation des sols argileux " et, - sur les techniques proposées pour amortir la gravité de sinistre induit par la sécheresse. Le programme d'essais en laboratoire a permis de déterminer la conductivité hydraulique, suivre la cinétique d'infiltration verticale dans une colonne de sol initialement non saturée et analyser de manière rigoureuse l'effet des conditions aux limites et des conditions initiales sur le phénomène. Pour suivre ce transfert en temps réel et en continu, un dispositif de mesure expérimental est mis au point. Il permet d'utiliser la méthode des profils instantanés avec mesure de succion à l'aide des papiers filtres. Les résultats ont montré que sur les échantillons compactés, l'augmentation de la teneur en eau initiale influence significativement l'évolution du profil de succion au cours de l'infiltration. Toutefois elle réduit la vitesse d'infiltration ainsi que l'avancement du front d'humidification. Par ailleurs l'augmentation de la charge hydraulique entraîne une augmentation de la profondeur de la zone d'humidification, mais elle n'influe pas la vitesse d'infiltration. L'étude expérimentale a permis de calculer le coefficient de perméabilité à saturation à partir de la connaissance du front d'humidification Zf. Lors des essais réalisés en place à l'aide d'infiltromètre à simple anneau, pour différentes charges hydrauliques positives appliquées à la surface du sol, la conductivité hydraulique ainsi que le potentiel d'écoulement matriciel ont été évalués selon différentes méthodes d'analyse des données d'infiltration. La thèse apporte, de plus, une contribution importante en matière d'évaluation de la gravité de la sécheresse sur les constructions. Cette partie vise principalement la qualification de la sévérité des sécheresses, afin de pouvoir décider de leur caractère catastrophique (anormal, exceptionnel) et de mettre en oeuvre le mécanisme d'indemnisation des dégâts dus à ces sécheresses par le système national d'indemnisation des catastrophes naturelles en France. Nous avons analysé les enregistrements de huit stations météorologiques mis à notre disposition par Météo France de 1950 à 2005. L'apport majeur de ce travail est la proposition d'un outil de classement des sécheresses dans une échelle de gravité significative du point de vue de la géotechnique. Ce mémoire s'achève par la vérification de l'hypothèse principale de travail qui est : un longue période de sécheresse est le principal facteur de déclenchement de ces mouvements. Les diagrammes ombrothermiques de Bagnouls et Gaussen pour des stations en région aride (période moyenne d'enregistrement de 20 ans) montrent l'intérêt des discussions en cours sur l'amplitude la vitesse et la localisation des différentes séquences sèches existantes dans les séries à partir de l'accumulation des anomalies pluviométriques décadaire

Modeling of Creep Behavior of an Argillaceous Rock by Numerical Homogenization Method

This paper is devoted to modeling the creep behavior of argillaceous rock and a comparison with experimental and numerical results from literature. The proposed time dependent modeling is based on a numerical homogenization method, matrix-inclusion material microstructure and a creep micromechanical model. The nonlinear viscosity of the argillaceous matrix is described by the creep model “Modified Time Hardening”, while classical linear elasticity is applied for the calcite and quartz inclusions. The simulation accuracy was analyzed under single and multistage creep test. A satisfactory agreement between the simulation and the experimental results are obtained by assuming the main mineral phases of the Callovo-Oxfordian argillite.  It was found that better agreements could be obtained when the multi-scale modeling is performed on sample with a given mineralogical composition and much more precisely volume fraction. The results show how numerical homogenization method is capable of effectively modelling macroscopic creep deformation