3805 results

  • Signal test for acoustic fibre optics for leakage detection of water bottoms

    Authors: Kruiver, P.; Obando Hernandez, E.; Pefkos, M.; Bremmer, C.N. (2019)

    The goal of this project is to analyse the results of the two large laboratory tests in order to assess whether distributed fibre optic sensing can detect the presence or absence of a clay layer in a water bottom. It is about a ‘signal test’ which must show that variations in lithology of the water bottom have an effect in the measured signal. The experiments for which the distributed fibre optic measurements have been performed consisted of experiments at a scale of 18 m x 5.5 m surface area and 2.5 m depth and for which fibre optics cable for acoustic and temperature measurements has been placed in a send bed of 80 cm thickness and covered with a clay layer of 10 cm. Three situations have been analysed.

  • Scaling point-scale (pedo)transfer functions to seamless large-domain parameter estimates for high resolution distributed hydrologic modeling : an example for the Rhine river

    Authors: Imhoff, R.O.; Verseveld, W.J. van; Osnabrugge, B. van; Weerts, A.H. (2020)
    Published in: Water resources research, volume 56 (2020) issue 4

    Moving toward high-resolution gridded hydrologic models asks for novel parametrization approaches. A high-resolution conceptual hydrologic model (wflow_sbm) was parameterized for the Rhine basin in Europe based on point-scale (pedo)transfer functions, without further calibration of effective model parameters on discharge. Parameters were estimated on the data resolution, followed by upscaling of parameter fields to the model resolution. The method was tested using a 6-hourly time step at four model resolutions (1.2, 2.4, 3.6, and 4.8 km), followed by a validation with discharge observations and a comparison with actual evapotranspiration (ETact) estimates from an independent model (DMET Land Surface Analysis Satellite Application Facility). Additionally, the scalability of parameter fields and simulated fluxes was tested. Validation of simulated discharges yielded Kling-Gupta Efficiency (KGE) values ranging from 0.6 to 0.9, except for the Alps where a volume bias caused lower performance. Catchment-averaged temporal ETact dynamics were comparable with independent ET estimates (KGE ≈ 0.7), although wflow_sbm model simulations were on average 115 mm yr−1 higher. Spatially, the two models were less in agreement (SPAEF = 0.10), especially around the Rhine valley. Consistent parameter fields were obtained, and by running the model at the different resolutions, preserved ETact fluxes were found across the scales. For recharge, fluxes were less consistent with relative errors around 30% for regions with high drainage densities. However, catchment-averaged fluxes were better preserved. Routed discharge in headwaters was not consistent across scales, although simulations for the main Rhine River were. Better processing (scale independent) of the river and drainage network may overcome this issue.

  • Geosynthetic-reinforced pile-supported embankments: state of the art

    Authors: Eekelen, S.J.M. van; Han, J. (2020)

    Geosynthetic-reinforced pile-supported embankments have been increasingly used worldwide to support earth structures. A significant amount of research has been conducted by many researchers and engineers in recent years. This paper provides a state-of-the-art review of this technology, and of important developments and results obtained throughout the years that help to better understand the mechanisms that play an important role in the design, construction, and performance of these systems. This paper begins with terminologies and historical developments. It then focuses on load transfer mechanisms and practical design and proposes topics for future research. The supplemental material gives tips for construction details and instrumentation for performance evaluation.

  • Deformations in trapdoor tests and piled embankments

    Authors: Rui, R.; Zhai, Y.X.; Han, J.; Eekelen, S.J.M. van; Chen, C. (2020)

    Fill deformation and surface settlement can be induced by differential settlement at the bottom of the fill in piled embankments. The deformation patterns and the relationship between the surface settlement and the differential settlement at the bottom of the fill have not been well investigated. Two-dimensional single-trapdoor, twin-trapdoor, and multi-trapdoor tests, including four tests with geosynthetic reinforcement, were conducted using elliptical steel rods as an analog to soil. The deformation pattern and influence regions in the single-trapdoor tests were evaluated using the measured deformations. The fill deformations in the trapdoor tests followed the Gaussian distribution.The superposition results of these Gaussian distribution curves of the single-trapdoor tests were compared with the measured deformations in the twin-trapdoor and multi-trapdoor tests. The differences between the measured and calculated results indicate that additional interaction occurred between adjacent trapdoors. The deformation shapes of the fill at the bottom of the geosyntheticreinforced and unreinforced test sections were different. However, the settlement pattern at the elevation level above 1.5 times the clear spacing of pile caps followed the same Gaussian distribution curve, if the volumetric settlement was the same. A method for predicting the surface settlement of 2D piled embankments is then presented.

  • Long term measurements in the Woerden geosynthetic-reinforced pile-supported embankment

    Authors: Eekelen, S.J.M. van; Venmans, A.A.M.; Bezuijen, A.; Tol, A.F. van (2020)

    The purpose of this paper is to present long-term measurements in a full-scale study on a basal reinforced piled embankment that make it possible to validate calculations used for the design of the geosynthetic reinforcement (GR). These calculations are normally carried out in two steps. To validate steps 1 and 2 together, it is necessary to measure GR strains. To validate calculation steps 1 and 2 separately, arching A needs to be measured, which is the pressure on the pile cap above the GR. An extensive monitoring project was conducted over a period of four years, in a basal reinforced piled embankment on 17 m of soft clay and peat. This study presents the measured GR strains and load distribution including arching, accompanied by measured groundwater levels and deformations. The subsoil support of the geosynthetic reinforcement disappeared quickly, arching developed over the first three months, and an annual cycle in the load distribution became apparent. Arching effects increase during the summer when conditions are relatively dry, resulting in a larger load on the piles and a reduction in the load on the GR. Additionally, the measured changes after an extremely rainy week are presented.

  • Computational material flow analysis for thousands of chemicals of emerging concern in European waters

    Authors: Gils, J.A.G. van; Posthuma, L.; Cousins, I.T.; Brack, W.; Altenburger, R.; Baveco, H.; Focks, A.; Greskowiak, J.; Kuhne, R.; Kutsarova, S.; Lindim, C.; Markus, A.A.; Meent, D. van de; Munthe, J.; Schueder, R.; Schuurmann, G.; Slobodnik, J.; Zwart, D. de; Wezel, A.P. van (2020)

    Knowledge of exposure to a wide range of chemicals, and the spatio-temporal variability thereof, is urgently needed in the context of protecting and restoring aquatic ecosystems. This paper discusses a computational material flow analysis to predict the occurrence of thousands of man-made organic chemicals on a European scale, based on a novel temporally and spatially resolved modelling framework. The goal was to increase understanding of pressures by emerging chemicals and to complement surface water monitoring data. The ambition was to provide a first step towards a “reallife” mixture exposure situation accounting for as many chemicals as possible. Comparison of simulated concentrations and chemical monitoring data for 226 substance/basin combinations showed that the simulated concentrations were accurate on average. For 65% and 90% of substance/basin combinations the error was within one and two orders of magnitude respectively. An analysis of the relative importance of uncertainties revealed that inaccuracies in use volume or use type information contributed most to the error for individual substances. To resolve this, we suggest better registration of use types of industrial chemicals, investigation of presence/absence of industrial chemicals in wastewater and runoff samples and more scientific information exchange.

  • Investigation of soil-arching development in dense sand by 2D model tests

    Authors: Rui, R.; Tol, A.F. van; Xia, Y.Y.; Eekelen, S.J.M. van; Hu, G. (2016)
    Published in: Geotechnical testing journal, volume 39 (2016) issue 3, page 415-430

    A trapdoor system has frequently been used to study soil arching and its development in recent years. The load transfer in the fill of piled embankments is very similar to a trapdoor system with multiple trapdoors. There are multiple arching models described in different standards and guidelines for piled embankments that can be subdivided into three archingmodel families. To study the soil-arching type and its development, a series of model tests with sand fills were carried out in a two-dimensional (2D) multi-trapdoor test setup. The tests considered four factors—the fill height, trapdoor width, pile width, and grain size of the sand—with four values for each factor. Triangular slip surfaces were found at very small deformations using the particle image velocimetry (PIV) technique. These surfaces evolved in ways that could be related to the three types of stress-distribution ratio curves, with development patterns similar to the arching families of piled embankments: (1) the rigidmodel family, (2) the equal-settlement-plane-model family, and (3) the limit-equilibriummodel family. The limit-equilibrium-model family occurred in tests with narrow trapdoor widths.

  • Shifting the discharge mind-set from harmful to habitat : exploring inventive designs and benefits of underwater discharge structures

    Authors: Merwe, R. van der; Morelissen, R.; Polman, H.; Jenner, H. (2019)

    With the aim to protect the marine environment, regulations have been set to regulate the brine discharges, and defining environmental criteria in the area close to the outfall. It was however noted, that such criteria are often adopted from generic benchmarks and sometimes from unadoptable locations. Robust and in situ research on the effects of the brine effluent on the marine environment is also lacking. Recent surveys however suggest that the ecological impact of brine outfalls can be very limited or even result in an improvement of biodiversity and marine abundance on the outfall structure. Such observations suggest that some environmental criteria may be archaic, which may result in needlessly expensive outfall designs.

  • Regional groundwater modelling for determining adaptation strategies in The Nile Delta aquifer

    Authors: Mabrouk, M.; Jonoski, A.; Oude Essink, G.H.P. (2019)

    Climate change, as predicted by several global climate models, is very likely to have severe future impacts, including sea-level rise. At the same time, population increase and development imperatives create additional pressure on available water resources. These changes are particularly problematic for the Mediterranean coastal areas, and especially the Nile Delta coast, causing increased salinity levels in groundwater. Particular focus of this study is on salinization of groundwater resources in the Nile Delta Aquifer (NDA) due to seawater intrusion. Groundwater quality in this area may significantly deteriorate in future, due to the impacts of sea level rise combined with excessive increase of groundwater extraction. To assess current conditions and develop future adaptation strategies for the NDA, a three-dimensional model simulating regional variable-density groundwater flow and coupled salt transport was constructed, using the SEAWAT code. For identifying the representative model for the seawater intrusion and salinity conditions in the NDA in the year 2010, a methodology of ‘evolving’ the conditions from completely fresh to salinized conditions using different simulation periods was used. This model was then applied to test the NDA conditions under several pre-defined scenarios of sea-level rise and groundwater extraction. Three different adaptation measures and their impacts in the Sharkeya Nile Delta governorate were initially tested, indicating that changing crops and irrigation practices to water saving options seems to be a promising measure, compared to artificial recharge with injection wells or extraction and usage of brackish groundwater after desalination. Studies with combinations of measures are further needed.

  • Co-design of an integrated operational water management tool for the Valle del Cauca, Colombia

    Authors: Ball, S.; Sanchez, M.F.; Werner, M.; Escobar Carmona, S.T.; Soto Chavez, C.Y.; Wuis, M.; Contreras, S.; Douben, K.J.; Visser, M.; Hunnink, J. (2019)

    This paper presents the developments of a tool for integrated water management (Herramienta para el Manejo Integral del Agua – HERMANA). HERMANA combines; real-time meteorological, hydrological, and water quality data and forecasts; information from an institutional database; surface water and groundwater models; and, drought indicators based on satellite data into a web-based platform. Together, these tools provide the basis to plan for integrated, operational water management. To optimize the usability of these tools, we implemented an intensive co-design framework that consisted of developing a number of use cases in collaboration with the end user, the Corporación Autónoma Regional del Valle del Cauca (CVC). These use cases provide CVC with a step-wise approach to deal with a number of water management issues. Results show the impact that an integrated operational tool can have at a number of levels within the organization by making the water resources information accessible and visible in a tailored way. However, the largest hurdle is not the integration of data systems and models, which is usually technically feasible, but rather the sustainable implementation and integration into the decision-making process of a water management authority’s organization. Our co-design approach included numerous interviews and workshops with CVC’s staff to better understand the decision-making process within the organization, the requisite data and information, how the data and information are used, and how it can be presented in such a way that it facilitates decision-making processes. Outcomes from these discussions and a roadmap for future implementation are presented.

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