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Sediment transport modelling in estuarine environments, characterised by cohesive and non-cohesive sediment mixtures, has to consider a time variation of erodibility due to consolidation. Generally, validated by settling column experiments, mud consolidation is now fairly well simulated; however, numerical models still have difficulty to simulate accurately the sedimentation and consolidation of mixed sediments for a wide range of initial conditions. This is partly due to the difficulty to formulate the contribution of sand in the hindered settling regime when segregation does not clearly occur. Based on extensive settling experiments with mud-sand mixtures, the objective of this study was to improve the numerical modelling of mixed-sediment consolidation by focusing on segregation processes. We used constitutive relationships following the fractal theory associated with a new segregation formulation based on the relative mud concentration. Using specific sets of parameters calibrated for each test—with different initial sediment concentration and sand content—the model achieved excellent prediction skills for simulating sediment height evolutions and concentration vertical profiles. It highlighted the model capacity to simulate properly the segregation occurrence for mud-sand mixtures characterised by a wide range of initial conditions. Nevertheless, calibration parameters varied significantly, as the fractal number ranged from 2.64 to 2.77. This study investigated the relevance of using a common set of parameters, which is generally required for 3D sediment transport modelling. Simulations were less accurate but remained satisfactory in an operational approach. Finally, a specific formulation for natural estuarine environments was proposed, simulating correctly the sedimentation-consolidation processes of mud-sand mixtures through 3D sediment transport modelling.

Sustainable development is one of the most important topics in today's world, and it is also an important research topic for geoenvironmental engineering. Dredging process is performed to expand the river and port channel, flood control and accessing harbors. Every year large amount of sediment are dredged for these purposes. Dredged marine soils can be reused as filling materials, road and foundation embankments, construction materials and wildlife habitat developments. In this study, geotechnical engineering properties and compressibility behavior of dredged soil obtained from the Izmir Bay were investigated. The samples with four different organic matter contents were obtained and particle size distributions, consistency limits, pH and specific gravity tests were performed. The consolidation tests were conducted to examine organic matter content (OMC) effects on compressibility behavior of dredged soil. This study has shown that the OMC has an important effect on the engineering properties of dredged soils. The liquid and plastic limits increased with increasing OMC. The lowest specific gravity belonged to sample which has the maximum OMC. The specific gravity values ranged between 2.76 and 2.52. The maximum void ratio difference belongs to sample with the highest OMC (De11% = 0.38). As the organic matter content of the samples increases, the change in the void ratio has also increased. The compression index increases with increasing OMC., {"references":["O. Ekincioglu, A. P. Gurgun, Y. Engin, M. Tarhan and S. Kumbaracibas, \"Approaches for sustainable cement production – A case study from Turkey,\" Elsevier Energy and Buildings, pp. 136–142, July 2013.","P. E. Martin, G. Bobillon and L. Eisenlohr, \"Reuse of solid waste from the clearing of road basins and ditches in civil engineering: From characterization to ways of treatment,\" in Proc. Meeting on Recent Developments in Sediment Transport and Management of Natural and Urban Sediments, Lyon, 2007, pp. 130–136.","L. Zhang, \"Production of bricks from waste materials - A review,\" Elsevier Construction and Building Materials, vol. 47, pp. 643–655, 2013.","B. V. Elkins and T. K. Thompson, \"Recycling dredge materials for beneficial use,\" in Proc. Dredging and Management of Dredged Material Session, Logan, July 1997, pp. 161–176.","J. Limeira, L. Agullo and M. Etxeberria \"Dredged marine sand as construction material,\" Integrated Environmental Assessment and Management, vol. 1, pp. 355–364, 2005.","W. S. Douglas, A. Maher and F. Jafari, \"Analysis of environmental effects of the use of stabilized dredged material from New York/New Jersey Harbor, USA, for construction of roadway embankments,\" European Journal of Environmental and Civil Engineering, vol. 16, pp. 311–315, 2012.","V. Dubois, N. E. Abriak and R. Zentar, \"The use of marine sediments as a pavement base material\", Waste Management, vol. 29, no. 2, pp, 774 –782, 2009.","D. Ganesalingam, A. Arulrajah, J. Ameratunga, P. Boyle and N. Sivakugan, \" Geotechnical properties of reconstituted dredged mud,\" Proceedings from the Pan-AM CGS Geotechnical Conference, pp. 1 – 7, Toronto, Canada, 2011.","M. Anisuzzaman and M. Arifuzzaman, \"Engineering properties of soft organic soil underlying dredge fill areas of Dhaka Bangladesh\", Proceeding from 2nd International Conference on Transport, Environment and Civil Engineering, Phnom Penh (Cambodia), Sept. 25-26, 2013. \n[10]\tZ. Shahri and C. Chan, \"On the characterization of dredged marine soils from Malaysian waters: physical properties,\" Environment and Pollution, vol. 4, No. 3, 2015.\n[11]\tB. F. Schlue, T. Mörz and S. Kreiter, \"Undrained shear strength properties of organic harbor mud at low consolidation stress levels,\" Canadian Geotechnical Journal, vol. 48, pp. 388–398, 2011.\n[12]\tP. K. Kolay, M. R. Aminur, S. N. L. Taib and M. I. S. Mohd Zain, \"Correlation between different physical and engineering properties of tropical peat soils from Sarawak,\" in Proc. GeoShanghai International Conference, Shanghai, 2010, No. 200. \n[13]\tS. Thiyyakkandi and S. Annex, \"Effect of organic content on geotechnical properties of Kuttanad clay,\" Electronic Journal of Geotechnical Engineering, vol. 16, 2011.\n[14]\tN. E. Malasavage, S. Jagupilla, D. G. Grubb, M. Wazne and W. P. Coon, \"Geotechnical performance of dredged material – steel slag fines blend: Laboratory and field evaluation,\" Journal of Geotechnical and Geoenviromental Engineering, vol. 138, No. 8, August 2012.\n[15]\tB. Ozkirli and O. Urker, \"İzmir Körfezi ve Limanı Rehabilitasyon Projesi kapsamında, Gediz Deltası sulak alanı içerisinde yapılması planlanan tarama malzemesi depolanması ve işlenmesi sürecinin ekolojik ve hukuki olarak incelenmesi\" Doğa Derneği, December 2012.\n[16]\tA. Filibeli, R. Yilmaz and I. Alyanak \"Dredged material of Izmir Harbor: Its behavior and pollution potential,\" Water Science & Technology Journal., vol. 32, no. 2, pp. 105–113, 1995.\n[17]\tASTM, American Society for Testing and Material, ASTM International, West Conshohocken, PA, www.astm.org.\n[18]\tG. Kocasoy, \"Atıksu arıtma çamuru ve katı atık ve kompost örneklerinin analiz yöntemleri,\" ISBN-13: 978-975-518-083-0, ISBN: 975-518-083-4, 1994."]}

This study attempts to model sediment transport rates and the resulting bed evolution in a complex estuarine environment: the Gironde estuary, characterized by a high hetereogeneity in the sediment bed composition, with the presence of both cohesive and non-cohesive sediments and sand/mud mixtures. Our main objective is to extend an existing 2D morphodynamic model developped by Huybrechts et al (2012b) for non-cohesive sediments, to account for the presence of mud and to draw some preliminary step for a fully mixte sediment morphodynamic model. Our framework is the finite element Telemac system (release 6.1), where the two-dimensional (depth averaged) approach has been selected for large scale and medium term simulations.The first part of this work is devoted to the understanding of sedimentation-consolidation processes for pure mud, combining laboratory experiments and 1D vertical models. Cohesive processes are then integrated in the 2D (depth-averaged) large scale morphodynamic model of the Gironde estuary developed by Huybrechts et al. (2012b). Erosion/deposition experiments were performed at the RWTH laboratory (University of Aachen, Germany) to calibrate the erosion and deposition law parameters. Moreover, the effect of consolidation is taken into account through the implementation of a 1DV Gibson-based sedimentation-consolidation model (Thiebot et al., 2011) using analytical closure equations for permeability and effective stress. Special attention is paid to the initialisation of the bed structure. Comparisons between measurements and model results are achieved on both suspended sediment concentration records and on medium term (5-year) bed evolutions.In the second part, a new 1DV model for the hindered settling of sand-mud mixtures has been developed based on the background of non-cohesive bi-disperse models. The numerical solution has been constructed by considering a high-order of accuracy in space via a Weighted Essentially Non Oscillatory (WENO) reconstruction technique and in time via a local space-time Discontinuous Galerkin (DG).The model is then validated against a large range of experimental data (mono-disperse sand, mud, non-cohesive bi-disperse and non-cohesive/cohesive mixture), Cette étude tente de modéliser les taux de transport de sédiments et l'évolution du lit dans un milieu estuarien complexe : l'estuaire de la Gironde, caractérisé par une grande hétérogénéité dans la composition des sédiments de lit, avec la présence de sédiments cohésifs et non-cohésifs ainsi que des mélanges sablo-vaseux. Notre objectif principal est d'étendre un modèle morphodynamique 2D développé par Huybrechts et al. (2012b) pour les sédiments non-cohésifs, afin de tenir compte de la présence de la vase et d'établir une étape préliminaire pour un modèle morphodynamique de sédiment mixte. Notre cadre est le système Telemac (version 6.1) où l'approche bi-dimensionnelle a été sélectionnée pour des simulations à grandes échelles spatiales (150 km) et moyen terme (5 ans).La première partie de ce travail est consacrée à la compréhension des processus de sédimentation-consolidation de la vase pure, en combinant expériences et modèles 1D verticaux. Les processus du sédiment cohésif sont ensuite intégrés dans le modèle morphodynamique de l'estuaire de la Gironde. Des expériences d'érosion et de dépôt ont été réalisées au laboratoire RWTH (Université d'Aachen, Allemagne) pour calibrer les paramètres des lois d'érosion et de dépôt. En outre, l'effet de la consolidation est pris en compte à travers la mise en œuvre d'un modèle 1DV de sédimentation et consolidation basé sur la théorie de Gibson (Thiébot et al., 2011) en utilisant des équations de fermeture analytique pour la perméabilité et la contrainte effective. Une attention particulière est accordée à l'initialisation de la structure verticale du lit sédimentaire. Les mesures et les résultats du modèle sont comparés pour les concentrations des sédiments en suspension et pour l'évolution de fond en moyen terme (5 ans).Dans la deuxième partie, un nouveau modèle 1DV pour la sédimentation entravée des mélanges sablo-vaseux a été développé sur la base des modèles de bi-disperse non-cohésifs. La solution numérique a été réalisée en prenant en considération un schéma de haute précision dans l'espace par la technique de reconstruction WENO et en temps par un Discontinue de Galerkin local (DG). Le modèle est ensuite validé par rapport à une large gamme de données expérimentales (mono-disperse sable, vase, non-cohésif bi-disperse et le mélange non-cohésif/cohesif)

This study attempts to model sediment transport rates and the resulting bed evolution in a complex estuarine environment: the Gironde estuary, characterized by a high hetereogeneity in the sediment bed composition, with the presence of both cohesive and non-cohesive sediments and sand/mud mixtures. Our main objective is to extend an existing 2D morphodynamic model developped by Huybrechts et al (2012b) for non-cohesive sediments, to account for the presence of mud and to draw some preliminary step for a fully mixte sediment morphodynamic model. Our framework is the finite element Telemac system (release 6.1), where the two-dimensional (depth averaged) approach has been selected for large scale and medium term simulations.The first part of this work is devoted to the understanding of sedimentation-consolidation processes for pure mud, combining laboratory experiments and 1D vertical models. Cohesive processes are then integrated in the 2D (depth-averaged) large scale morphodynamic model of the Gironde estuary developed by Huybrechts et al. (2012b). Erosion/deposition experiments were performed at the RWTH laboratory (University of Aachen, Germany) to calibrate the erosion and deposition law parameters. Moreover, the effect of consolidation is taken into account through the implementation of a 1DV Gibson-based sedimentation-consolidation model (Thiebot et al., 2011) using analytical closure equations for permeability and effective stress. Special attention is paid to the initialisation of the bed structure. Comparisons between measurements and model results are achieved on both suspended sediment concentration records and on medium term (5-year) bed evolutions.In the second part, a new 1DV model for the hindered settling of sand-mud mixtures has been developed based on the background of non-cohesive bi-disperse models. The numerical solution has been constructed by considering a high-order of accuracy in space via a Weighted Essentially Non Oscillatory (WENO) reconstruction technique and in time via a local space-time Discontinuous Galerkin (DG).The model is then validated against a large range of experimental data (mono-disperse sand, mud, non-cohesive bi-disperse and non-cohesive/cohesive mixture), Cette étude tente de modéliser les taux de transport de sédiments et l'évolution du lit dans un milieu estuarien complexe : l'estuaire de la Gironde, caractérisé par une grande hétérogénéité dans la composition des sédiments de lit, avec la présence de sédiments cohésifs et non-cohésifs ainsi que des mélanges sablo-vaseux. Notre objectif principal est d'étendre un modèle morphodynamique 2D développé par Huybrechts et al. (2012b) pour les sédiments non-cohésifs, afin de tenir compte de la présence de la vase et d'établir une étape préliminaire pour un modèle morphodynamique de sédiment mixte. Notre cadre est le système Telemac (version 6.1) où l'approche bi-dimensionnelle a été sélectionnée pour des simulations à grandes échelles spatiales (150 km) et moyen terme (5 ans).La première partie de ce travail est consacrée à la compréhension des processus de sédimentation-consolidation de la vase pure, en combinant expériences et modèles 1D verticaux. Les processus du sédiment cohésif sont ensuite intégrés dans le modèle morphodynamique de l'estuaire de la Gironde. Des expériences d'érosion et de dépôt ont été réalisées au laboratoire RWTH (Université d'Aachen, Allemagne) pour calibrer les paramètres des lois d'érosion et de dépôt. En outre, l'effet de la consolidation est pris en compte à travers la mise en œuvre d'un modèle 1DV de sédimentation et consolidation basé sur la théorie de Gibson (Thiébot et al., 2011) en utilisant des équations de fermeture analytique pour la perméabilité et la contrainte effective. Une attention particulière est accordée à l'initialisation de la structure verticale du lit sédimentaire. Les mesures et les résultats du modèle sont comparés pour les concentrations des sédiments en suspension et pour l'évolution de fond en moyen terme (5 ans).Dans la deuxième partie, un nouveau modèle 1DV pour la sédimentation entravée des mélanges sablo-vaseux a été développé sur la base des modèles de bi-disperse non-cohésifs. La solution numérique a été réalisée en prenant en considération un schéma de haute précision dans l'espace par la technique de reconstruction WENO et en temps par un Discontinue de Galerkin local (DG). Le modèle est ensuite validé par rapport à une large gamme de données expérimentales (mono-disperse sable, vase, non-cohésif bi-disperse et le mélange non-cohésif/cohesif)

The silting up process and the stability of muddy massifs are strongly dependent on the behaviour of clay-rich and high watercontent soils. The characteristics of such soils are complex and they evolve much. Depending on the environmental conditions, the material can be either a liquid or a solid. The modelling of the formation and of the degradation of muddy massifs has been studied by focusing both on the deposition/consolidation process and on the appearance of slope failures. A model based on the Gibson's theory wich simulates the evolution of mud deposits caused by hindered settling and by consolidation processes has been designed. it has been inserted in a model which similates the sediment transport in the Rance estuary (France). The new management of the muddy deposits has improved the way exchanges between the dilute suspension and the bottom are simulated. The distribution of suspended sediment has been modified and the mud deposits have been distributed in a new manner. A model bades on a finite element method has been designed in order to study the influence of various loading on slides. An application has been carried out on the Sèvre Niortaise (Frence). Laboratory tests and in situ measurements have been performed. Those have shown that the wetting-drying cycles play an important role in the degradation of the banks., Les mécanismes d'envasement et la stabilité des talus vaseux sont fortement conditionnés par le comportement de sols argileux à forte teneur en eau. Situés à la frontière entre l'état liquide et l'état solide, ces matériaux sont évolutifs et possèdent des caractéristiques complexes. La modélisation de la formation et de la dégradation des massifs vaseux a été étudiée en se focalisant sur les processus de dépôt et de consolidation sous poids propre et sur l'apparition de glissements. Nous avons développé un modèle basé sur la théorie de Gibson qui gère l'évolution des dépôts vaseux soumis à la chute entravée et à la consolidation. Il a été intégré dans un système de modélisation hydrosédimentaire. Une application a été réalisée sur l'estuaire de la Rance. Les échanges entre la suspension et le fond sont simulés plus fidèlement avec le nouveau modèle de gestion des dépôts vaseux. La carte des dépôts et la distribution de matières en suspension simulées ont été fortement modifiées. Un modèle numérique de talus basé sur un calcul par éléments finis a été conçu pour étudier l'influence de différents chargements mécaniques sur l'apparition de glissements. Une application a été réalisée sur les berges de la Sèvre Niortaise. Parallèlement à l'étude de modélisation, des essais de laboratoire et des mesures in situ ont mis en évidence le rôle des phénomènes de retrait/gonflement dans la dégradation des berges.