4209 resultaten

  • IJkdijk full scale underseepage erosion (piping) test : evaluation of innovative sensor technology

    Auteurs: Vries, G. de; Koelewijn, A.R.; Hopman, V. (2010)

  • Intercomparison of three morphodynamic models for the Lower Yellow River

    Auteurs: Xia, J.Q.; Wang, Z.B.; Maren, D.S. van (2010)

    Significant channel adjustment often occurs in the Lower Yellow River (LYR), and it is a challenging work to simulate the morphodynamic processes in the LYR using numerical models. An intercomparison of three morphodynamic models (Delft3D, 2DLLCDM and 2DRPM) for the LYR is presented herein. The models are first compared with each other in the model concepts, and are then used to simulate the morphodynamic processes in a braided reach of the LYR.

  • Semi-empirical estimation of organic compound fugacity ratios at environmentally relevant system temperatures

    Auteur: Noort, P.C.M. van (2009)
    Gepubliceerd in: Chemosphere, volume 76 (2009) nummer 1, pagina 16-21

    Semi-empirical compound class specific equations were derived to estimate fugacity ratios from molecular weight and melting temperature for polycyclic aromatic hydrocarbons and polychlorinatedbenzenes, biphenyls, dibenzo[p]dioxins and dibenzofurans.

  • The impact of water diversion on river morphology and its implications for the Lower Yellow River

    Auteurs: Li, W.; Wang, Z.B.; Vriend, H.J. de (2010)

    Extensive water diversion, such as the irrigation projects in the Yellow River basin in China, may cause significant discharge reduction and thus have a considerable effect on fluvial processes. According to previous work, the river bed will become convex, but this is based upon a series of assumptions, such as constant width and continuous diversion, and it does not provide any ability to predict the time scale at which the impact of the water diversion will develop.

  • Detection of low bottom water oxygen concentrations in the North Sea : implications for monitoring and assessment of ecosystem health

    Auteurs: Greenwood, N.; Laane, R.W.P.M. (2010)
    Gepubliceerd in: Biogeosciences, volume 7 (2010) nummer 4, pagina 1357-1373

    This paper presents new results from high temporal resolution observations over two years (2007 and 2008) from instrumented moorings deployed in the central NorthSea, at the Oyster Grounds and on the northern slope of Dogger Bank (North Dogger).

  • Effect of different sediment mixtures on the long-term morphological simulation of tidal basins

    Auteurs: Dastgheib, A.; Roelvink, J.A. (2009)

  • Shear-induced flocculation of a suspension of kaolinite as function of pH and salt concentration

    Auteurs: Mietta, F.; Chassagne, C.; Winterwerp, J.C. (2009)

     The settling velocity of sediment particles governs to a large extent the transport of fine sediment in open water systems, such as rivers, estuaries, and seas. Cohesive sediment flocculates and its floc size and settling velocity vary with the environmental conditions. It is difficult to measure flocs properties in situ because flocs are fragile and the environment is highly dynamic.

  • Reconstructing the early 19th-century Waal River by means of a 2D physics-based numerical model

    Auteurs: Montes Arboleda, A.; Crosato, A.; Middelkoop, H. (2010)
    Gepubliceerd in: Hydrological processes : an international journal, volume 24 (2010) nummer 25, pagina 3661-3675

  • Nonlinear terms in storm surge predictions : effect of tide and shelf geometry with case study from hurricane Rita

    Auteurs: Lima Rego, J.R.; Li, C. (2010)
    Gepubliceerd in: Journal of geophysical research, C : oceans, volume 115 (2010), pagina 1019

    This study applied the finite volume coastal ocean model (FVCOM) to the storm surge induced by Hurricane Rita along the Louisiana - Texas coast. Peak water levels were shown to be lower than expected for a landfall at high tide. For low and high tide landfalls, nonlinear effects due to tide?surge coupling were constructive and destructive to total storm tide, respectively.

  • Lateral loading of pile foundations due to embankment construction

    Auteurs: Feddema, A.; Breedeveld, J.; Tol, A.F. van (2010)

    The objective of this research work was to gain a better understanding of the interaction between loads applied on the surface of soils, and the behaviour of adjacent long, vertical piles, embedded at depth in a stiff substratum. The influence of lateral thrust on the piles in an upper soft clay layer, due to simulated embankment construction, was examined and soil-pile interaction mechanisms were identified both for behaviour at working load and at the ultimate lateral capacity. The performance of a row of free headed piles and of a pile group were investigated experimentally in the geotechnical centrifuge (Deltares) for different pile and foundation geometries. Pile response, in terms of bending moment, deflection and lateral pressure, was determined for surcharge loads applied to the centrifuge model. This experimental database was used to calibrate a three dimensional finite element analysis of the same, simplified, model. These investigations led to the development of an approximate formula for lateral loading, based on the differential movement between the piles and the surrounding soil, which accounted for pile spacing. relative pile-soil stiffness and the degree of soil strength mobilisation. This loading function was incorporated in a computer program, SIMPLE, which calculated the pile bending moment and deflection profiles for flexible piles and pile groups. The algorithm was checked against the centrifuge model test results and the numerical analyses, and design charts were produced for free headed piles only_ Finally a design procedure was recommended for piled full-height bridge abutments and other facilities which feature passive lateral loading of piles by a nearby surcharge.

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