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Hocine Oumeraci - One of the best experts on this subject based on the ideXlab platform.
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soil stability analysis for wave induced momentary liquefaction beneath porous bonded Revetments
Coastal Engineering, 2018Co-Authors: Juan Carlos Alcerrecahuerta, Hocine OumeraciAbstract:Abstract The highly porous Revetments made of Polyurethane Bonded Aggregates (PBA) are an ecologically friendly alternative to conventional Revetments for protection against coastal erosion. No information has yet been reported for these structures on failures from field applications. However, a well-documented collapse of a PBA-revetment observed in large-scale tests (GWK tests) and a first stability analysis were reported by Oumeraci et al., 2010; 2012. Based on these results, a methodology is proposed for stability analysis of the embankment subsoil beneath PBA-Revetments against momentary liquefaction, considering the results of the comprehensive parametric study (Alcerreca-Huerta, 2014) using a recently developed CFD-CSD (Computational Fluids Dynamics- Computational Solid Dynamics) model wavePoreGeoFoam (Alcerreca-Huerta and Oumeraci, 2016a; 2016b). It will be shown that the proposed stability analysis is able to reproduce the failure observed in the GWK tests, so that it can be applied for PBA-revetment under field conditions. In this paper, the failure observed in the GWK tests is first briefly reported, followed by a description of the numerical parametric study using the validated wavePoreGeoFoam model in order to extend the conditions tested in GWK. Then, the processes underlying soil liquefaction of PBA-Revetments are outlined, showing that the excess pore pressure development in the sand core beneath PBA-Revetments is crucial. The latter is therefore examined and a formula to predict excess pore pressures in terms of the wave conditions is developed. Moreover, a methodology for the stability analysis of the soil beneath the revetment against soil liquefaction is proposed and implemented to reproduce the failure observed in the GWK tests. Finally, the main results are summarized and implications for further research are drawn.
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wave induced pressures in porous bonded Revetments part i pressures on the revetment
Coastal Engineering, 2016Co-Authors: Juan Carlos Alcerrecahuerta, Hocine OumeraciAbstract:Abstract Revetments made of polyurethane bonded aggregates (PBA) are a recent alternative to mitigate coastal erosion. Their advantages over conventional impermeable Revetments are shown in previous studies, based on large-scale laboratory tests (Oumeraci et al., 2010) and CFD modelling (Foyer and Oumeraci, 2013). The latter were conducted to describe the hydrodynamic and hydro-geotechnical processes involved in the wave–structure interaction with PBA Revetments. However, the data generated did not allow a full description of the wave-induced loading of the revetment and the response of the underlying soil; therefore, a comprehensive parameter study with a computational fluids dynamics–computational solid dynamics (CFD–CSD) model system was performed. This paper (Part I) focuses on the wave-induced pressures on the revetment, while a companion paper (Part II) describes the pore pressure development just beneath the revetment and in the embankment subsoil. In this first part, the following issues are addressed: (i) introduction to the numerical parameter study and the CFD–CSD model used for the modelling of the wave-induced pressures; (ii) brief review of the wave load classification and parameterization to define the elements and notations for the wave-induced pressure analysis; (iii) analysis of the peak pressure magnitude, its location on the revetment, and the spatial pressure distribution; and (iv) the development of prediction formulae, based on the results of the analysis in issue iii. Finally, a summary of the key results and concluding remarks are provided, including the implications and recommendations for engineering applications as well as for further research.
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wave induced pressures in porous bonded Revetments part ii pore pressure just beneath the revetment and in the embankment subsoil
Coastal Engineering, 2016Co-Authors: Juan Carlos Alcerrecahuerta, Hocine OumeraciAbstract:Abstract This paper considers pore pressure distribution in the embankment subsoil beneath PBA-Revetments, based on the results of the parameter study using the new validated CFD–CSD model system wavePoreGeoFoam described in the companion paper (Part I), which focusses on wave-induced pressures on PBA-Revetments (Alcerreca-Huerta and Oumeraci, 2016-in this issue). In this paper (Part II), a general overview is first provided on the numerical parameter study, especially on the model setup for the extraction of data related to the wave-induced pore pressures in the sand core beneath PBA-Revetments. Secondly, wave-induced pore pressure just beneath the revetment is analysed considering: peak pressure magnitude, its location beneath the revetment and their spatial distribution. Afterwards, a process analysis of the results of the parameter study is performed for the wave-induced pore pressure distribution in the sand core. Formulae are developed for the prediction of the pore pressure distribution just beneath the revetment and of the damping of peak pore-pressures in the sand core. Subsequently, a comparative analysis of the proposed formulae and the approach of De Groot et al. (2006) for the assessment of pore pressure in a porous seabed is made, showing a very good agreement between both results. Finally, implications and recommendations for engineering applications and for further research are drawn from the results.
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cfd csd numerical modelling of wave induced pressures in open pored pba Revetments
Coastal Engineering Proceedings, 2014Co-Authors: Juan Carlos Alcerreca Huerta, Hocine OumeraciAbstract:The highly porous Polyurethane Bonded Aggregates (PBA) Revetments represent a novel ecologically friendly solution for the protection of shorelines and vulnerable coastal areas against erosion. Advantages of the open-pored PBA-Revetments over conventional smooth impermeable Revetments are among others, the reduction of: wave run- up/run-down, wave reflection and wave-induced loads on the sand core beneath the revetment. However, the hydro- geotechnical processes involved in the interaction of waves with such PBA-Revetments and their foundation are still not sufficiently understood. Therefore, a new 3-dimensional one-way coupled CFD-CSD model system "wavePoreGeoFoam" was developed at the Leichtweis-Institute (LWI) within the OpenFOAM® framework for the analysis of the response of open-pored PBA-Revetments due to wave-induced loads. In this way, this paper firstly describes the new CFD-CSD model system. Second, validation of the model "wavePoreGeoFoam" is shown considering large-scale laboratory tests performed in the Large Wave Flume (GWK) at the Coastal Research Center (FZK) in Hanover, Germany (Oumeraci et al. 2010). Third, the relevance of implementing the CFD-CSD coupling for modelling wave-induced pressures on and beneath PBA-Revetments is discussed. Fourth, a sensitivity analysis related to the effect of the empirically defined parameters for the numerical model is described. Finally, recommendations and implications of the use of CFD-CSD model for further research will be addressed.
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effect of porosity and slope steepness on wave induced loads on and beneath bonded porous Revetments
34th International Conference on Coastal Engineering (ICCE 2014), 2014Co-Authors: Sven Liebisch, Andreas Kortenhaus, Hocine OumeraciAbstract:The porosity and the slope steepness of bonded Revetments both affect wave-induced loads on and beneath the Revetments and are thus crucial for the stability and durability of the entire structure. This is shown by the selected results of the three years German research project BoPoRe (Bonded Porous Revetments) which has the primary objective to systematically investigate the effect of the porosity, roughness and slope steepness on different loading parameters and to develop process-based and generic design formulae that explicitly account for the porosity and other structure parameters. The paper briefly introduces the project and discusses selected results of the main model tests using 3 different scaled model configurations. All configurations used a polyurethane bonded aggregate (PBA) cover layer and tests were performed with random waves.
Torsten Schlurmann - One of the best experts on this subject based on the ideXlab platform.
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full scale experimental study on wave overtopping at stepped Revetments
Coastal Engineering, 2021Co-Authors: Talia Schoonees, Nils B Kerpen, Torsten SchlurmannAbstract:Abstract Stepped Revetments limit wave overtopping effectively. Small-scale studies provided insights in the design of crest-levels and step geometries of these structures. The validation of these insights at large scale, along with the analysis of individual overtopping volumes, is required to formulate design recommendations. This paper investigates wave overtopping rates and individual overtopping volumes at stepped Revetments by means of full-scale flume experiments. Two cross-sections, each with a slope of 1:3, were studied with uniform step heights of 0.17 m and 0.50 m. The Revetments reduced wave overtopping rates in comparison to smooth dikes, resulting in influence factors for roughness (γf) between 0.43 and 0.73. An empirical formula for γf is proposed with which the wave overtopping rate at stepped Revetments can be estimated. Previous small-scale studies underestimate γf of this study by 2–31 % . Individual overtopping volumes were described by a Weibull distribution, revealing a higher median shape factor (b=1.63) for stepped Revetments compared to breakwaters, smooth dikes or vertical walls.
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wave overtopping of stepped Revetments
2019Co-Authors: Nils B Kerpen, Talia Schoonees, Torsten SchlurmannAbstract:Wave overtopping—i.e., excess of water over the crest of a coastal protection infrastructure due to wave run-up—of a smooth slope can be reduced by introducing slope roughness. A stepped revetment ideally constitutes a slope with uniform roughness and can reduce overtopping volumes of breaking waves up to 60% compared to a smooth slope. The effectiveness of the overtopping reduction decreases with increasing Iribarren number. However, to date a unique approach applicable for a wide range of boundary conditions is still missing. The present paper: (i) critically reviews and analyzes previous findings; (ii) contributes new results from extensive model tests addressing present knowledge gaps; and (iii) proposes a novel empirical formulation for robust prediction of wave overtopping of stepped Revetments for breaking and non-breaking waves. The developed approach contrasts a critical assessment based on parameter ranges disclosed beforehand between a smooth slope on the one hand and a plain vertical wall on the other. The derived roughness reduction coefficient is developed and adjusted for a direct incorporation into the present design guidelines. Underlying uncertainties due to scatter of the results are addressed and quantified. Scale effects are highlighted.
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Development of an Outdoor Wave Basin to Conduct Long-Term Model Tests with Real Vegetation for Green Coastal Infrastructures
MDPI AG, 2019Co-Authors: Jochen Michalzik, Sven Liebisch, Torsten SchlurmannAbstract:The demand for physical model tests with real vegetation is increasing due to the current trend to elucidate the performance and durability of green coastal infrastructures to ensure and promote ecosystem services. To address this demand, a new outdoor wave basin (OWB) was built in August 2017 at the Ludwig-Franzius-Institute in Hannover, Germany. This paper reviews the general characteristics and the ongoing development of the new OWB. First insights into the long-term development of the ecosystem services of different grass Revetments are discussed in terms of their ecological value and safety standards of sea dikes. Focus is placed on the resistance and ecological value of different grass mixtures that are typically applied on sea dikes situated along the North Sea. Further research concepts are briefly described to highlight how experiments in the new OWB may contribute to the current understanding and design recommendations of green coastal infrastructures. The operation of the OWB enables the performance of long-term experiments over seasonal growth stages of coastal vegetation using either fresh or seawater with wave load stresses and varying sea water levels. The first conducted experiments with different grass revetment combinations mimic typical storm surge conditions with a constant wave load (with a duration of up to 10 hours every second week) on a natural dike
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effects of wave load on the long term vegetation development and their resistance as grass Revetments on sea dikes
Coastal Engineering Proceedings, 2018Co-Authors: Jochen Michalzik, Sven Liebisch, Torsten SchlurmannAbstract:Construction and design processes of Revetments, sea dikes and estuarine dikes along the German coastline adhere the paradigm to protect and safeguard reliably the coastal hinterland from wave attack and storm surges. Following these standards coastal protection structures provide only poor ecosystem services in any proper design or maintenance approach. As a result, the EcoDike-project has been started with the aim to quantify and enhance the ecosystem services of Revetments, sea dikes and estuarine dikes while preserving or possibly even enhancing the existing safety standards. Therefore, a profound understanding of the complex long-term interactions between wave load and vegetation development on sea dikes is inevitable. To achieve these objectives a typical seadike in prototype scale is tested under realistic and long-term wave loading in the new outdoor wave basin at the Ludwig-Franzius-Institute in Hannover (Germany).
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wave impact pressures on stepped Revetments
Journal of Marine Science and Engineering, 2018Co-Authors: Nils B Kerpen, Talia Schoonees, Torsten SchlurmannAbstract:The wave impacts on horizontal and vertical step fronts of stepped Revetments is investigated by means of hydraulic model tests conducted with wave spectra in a wave flume. Wave impacts on Revetments with relative step heights of 0.3 < Hm0/Sh < 3.5 and a constant slope of 1:2 are analyzed with respect to (1) the probability distribution of the impacts, (2) the time evolution of impacts including a classification of load cases, and (3) a special distribution of the position of the maximum impact. The validity of the approved log-normal probability distribution for the largest wave impacts is experimentally verified for stepped Revetments. The wave impact properties for stepped Revetments are compared with those of vertical seawalls, showing that their impact rising times are within the same range. The impact duration for stepped Revetments is shorter and decreases with increasing step height. Maximum horizontal wave impact loads are about two times larger than the corresponding maximum vertical wave impact loads. Horizontal and vertical impact loads increase with a decreasing step height. Data are compared with findings from literature for stepped Revetments and vertical walls. A prediction formula is provided to calculate the maximum horizontal wave impact at stepped Revetments along its vertical axis.
Juan Carlos Alcerrecahuerta - One of the best experts on this subject based on the ideXlab platform.
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soil stability analysis for wave induced momentary liquefaction beneath porous bonded Revetments
Coastal Engineering, 2018Co-Authors: Juan Carlos Alcerrecahuerta, Hocine OumeraciAbstract:Abstract The highly porous Revetments made of Polyurethane Bonded Aggregates (PBA) are an ecologically friendly alternative to conventional Revetments for protection against coastal erosion. No information has yet been reported for these structures on failures from field applications. However, a well-documented collapse of a PBA-revetment observed in large-scale tests (GWK tests) and a first stability analysis were reported by Oumeraci et al., 2010; 2012. Based on these results, a methodology is proposed for stability analysis of the embankment subsoil beneath PBA-Revetments against momentary liquefaction, considering the results of the comprehensive parametric study (Alcerreca-Huerta, 2014) using a recently developed CFD-CSD (Computational Fluids Dynamics- Computational Solid Dynamics) model wavePoreGeoFoam (Alcerreca-Huerta and Oumeraci, 2016a; 2016b). It will be shown that the proposed stability analysis is able to reproduce the failure observed in the GWK tests, so that it can be applied for PBA-revetment under field conditions. In this paper, the failure observed in the GWK tests is first briefly reported, followed by a description of the numerical parametric study using the validated wavePoreGeoFoam model in order to extend the conditions tested in GWK. Then, the processes underlying soil liquefaction of PBA-Revetments are outlined, showing that the excess pore pressure development in the sand core beneath PBA-Revetments is crucial. The latter is therefore examined and a formula to predict excess pore pressures in terms of the wave conditions is developed. Moreover, a methodology for the stability analysis of the soil beneath the revetment against soil liquefaction is proposed and implemented to reproduce the failure observed in the GWK tests. Finally, the main results are summarized and implications for further research are drawn.
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wave induced pressures in porous bonded Revetments part i pressures on the revetment
Coastal Engineering, 2016Co-Authors: Juan Carlos Alcerrecahuerta, Hocine OumeraciAbstract:Abstract Revetments made of polyurethane bonded aggregates (PBA) are a recent alternative to mitigate coastal erosion. Their advantages over conventional impermeable Revetments are shown in previous studies, based on large-scale laboratory tests (Oumeraci et al., 2010) and CFD modelling (Foyer and Oumeraci, 2013). The latter were conducted to describe the hydrodynamic and hydro-geotechnical processes involved in the wave–structure interaction with PBA Revetments. However, the data generated did not allow a full description of the wave-induced loading of the revetment and the response of the underlying soil; therefore, a comprehensive parameter study with a computational fluids dynamics–computational solid dynamics (CFD–CSD) model system was performed. This paper (Part I) focuses on the wave-induced pressures on the revetment, while a companion paper (Part II) describes the pore pressure development just beneath the revetment and in the embankment subsoil. In this first part, the following issues are addressed: (i) introduction to the numerical parameter study and the CFD–CSD model used for the modelling of the wave-induced pressures; (ii) brief review of the wave load classification and parameterization to define the elements and notations for the wave-induced pressure analysis; (iii) analysis of the peak pressure magnitude, its location on the revetment, and the spatial pressure distribution; and (iv) the development of prediction formulae, based on the results of the analysis in issue iii. Finally, a summary of the key results and concluding remarks are provided, including the implications and recommendations for engineering applications as well as for further research.
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wave induced pressures in porous bonded Revetments part ii pore pressure just beneath the revetment and in the embankment subsoil
Coastal Engineering, 2016Co-Authors: Juan Carlos Alcerrecahuerta, Hocine OumeraciAbstract:Abstract This paper considers pore pressure distribution in the embankment subsoil beneath PBA-Revetments, based on the results of the parameter study using the new validated CFD–CSD model system wavePoreGeoFoam described in the companion paper (Part I), which focusses on wave-induced pressures on PBA-Revetments (Alcerreca-Huerta and Oumeraci, 2016-in this issue). In this paper (Part II), a general overview is first provided on the numerical parameter study, especially on the model setup for the extraction of data related to the wave-induced pore pressures in the sand core beneath PBA-Revetments. Secondly, wave-induced pore pressure just beneath the revetment is analysed considering: peak pressure magnitude, its location beneath the revetment and their spatial distribution. Afterwards, a process analysis of the results of the parameter study is performed for the wave-induced pore pressure distribution in the sand core. Formulae are developed for the prediction of the pore pressure distribution just beneath the revetment and of the damping of peak pore-pressures in the sand core. Subsequently, a comparative analysis of the proposed formulae and the approach of De Groot et al. (2006) for the assessment of pore pressure in a porous seabed is made, showing a very good agreement between both results. Finally, implications and recommendations for engineering applications and for further research are drawn from the results.
Shengquan Che - One of the best experts on this subject based on the ideXlab platform.
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effects of Revetments on soil denitrifying communities in the urban river riparian interface
Chemosphere, 2021Co-Authors: Lubing Yan, Changkun Xie, Anze Liang, Ruiyuan Jiang, Shengquan CheAbstract:Abstract The river-riparian interface plays an important role in removal of nitrogen pollution. Many Revetments have been built in urban riparian zones, which has affected soil denitrification function of river-riparian interface. However, the impacts of Revetments on denitrifying communities of soil in the river-riparian interface are still unclear. In this study, in the case of eliminating the influence of plants, three modes of Revetments (No Revetments (NR), Impervious Masonry Revetments (IR), and Permeable Concrete Imitation Pile Revetments (PR)) were employed to determine the influence of Revetments on denitrifying communities of soil among three distances from Revetments (1.0, 0.6 and 0.3 m). It was shown in comparison with IR and NR, PR promoted the abundance, diversity and relative abundance of major strains in nirS and nirK denitrifying bacteria (P
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the influence of revetment types on soil denitrification in the adjacent tidal urban riparian zones
Journal of Hydrology, 2019Co-Authors: Lubing Yan, Changkun Xie, Shengquan CheAbstract:Abstract Riparian zones adjacent to Revetments, as the last position of the entire riparian, are the last barrier to intercept runoff nitrogen pollution. They are also the areas where hyporheic exchange occurs when soil is submerged by river water. Revetments can be classified into impervious Revetments and permeable Revetments according to their permeability. It has been realized that impervious Revetments are not conducive to exchange between rivers and riparian zones. Tidal riparian zones undergo water level changes more frequently than normal riparian zones. Thus, Revetments in tidal riparian zones may have a greater impact on nitrogen cycling. However, the quantitative influence of revetment types on nitrogen removal in adjacent tidal urban riparian zones is not clear, resulting in the lack of scientific support for the Revetments construction. Removal of nitrogen from riparian zones primarily occurs through plant uptake, microbial immobilization, and denitrification. However, nitrogen will be released into soil again after plants die or microorganisms decompose. While denitrification can completely remove nitrogen through transferring nitrate (NO3−) into gaseous nitrous oxide (N2O) and dinitrogen (N2). In this study, we used three revetment types (permeable concrete pile Revetments (PR), impervious masonry stone Revetments (IR), and no Revetments (NR)) as examples to quantify the effects of revetment types on soil denitrification in adjacent tidal urban riparian zones at three distances from the Revetments (0.3 m, 0.6 m, 1.0 m) by measuring the soil (0–20 cm) denitrification potential (DP) and N2O production rates (N2OR). Results indicated that compared with soil denitrification (0.32 ± 0.06 mg kg−1h−1) in natural riparian zones (NR), PR could significantly improve it (0.97 ± 0.07 mg kg−1h−1), while IR significantly inhibited it (0.23 ± 0.04 mg kg−1h−1) in the adjacent tidal urban riparian zones (P
Adam Bezuijen - One of the best experts on this subject based on the ideXlab platform.
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design formulas for block Revetments
Journal of Waterway Port Coastal and Ocean Engineering-asce, 1996Co-Authors: Adam Bezuijen, Mark Klein BretelerAbstract:Design formulas for placed block Revetments are evaluated. The various formulas, as published in literature, have a different background or are based on different experiments. Most formulas are based on an analytical solution of a ground-water flow equation for the flow in the filter layer and a schematized pressure distribution on the slope due to wave attack. Empirical formulas describing the wave pressure distribution as a function of wave height, wave steepness, and slope are presented. The pressure distribution used was based on experiments with regular waves. Recent experiments provide the opportunity to improve the wave pressure distribution, using the results of irregular waves. The resulting design formulas are described. These design formulas are based on laminar flow. The influence of turbulent flow is investigated. The formulas are used in a calculation example. It is shown that the permeabilities of cover layer and filter layer are very important for the maximum wave height the revetment can withstand.
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wave forces and structure response of placed block Revetments on inclined structures
Int. Conf. on Coastal Engineering 1995, 1995Co-Authors: K W Pilarczyk, Klein M Breteler, Adam BezuijenAbstract:A summary of the theoretical and empirical knowledge of the stability of block-revetment structures under wave attack is given. This has been accomplished by selecting the very essence of the design formulas from (CUR/TAW, 1992/1994) and completing it afterwards with a database of results of large-scale model studies from all over the world. Furthermore, the additional filter criteria and geotechnical criteria will be presented. For each of these mechanisms easy to use design formulas are given. Finally, the specific design considerations related to block Revetments will be discussed.
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OBLIQUE WAVE ATTACK ON BLOCK Revetments
1993Co-Authors: Adam Bezuijen, Mark Klein BretelerAbstract:The influence of the angle of the incoming wave on the stability of a placed block revetment on a filter layer has been investigated. A computer program is described to simulate the flow in the filter layer for various wave conditions. The flow in the filter layer together with the wave conditions determine the loading on the revetment. Two different boundary conditions have been studied, A schemed wave pressure distribution based on results obtained for wave loading perpendicular to the revetment and regular waves measured in a wave basin. The results show that for regular waves the influence of the angle of the incoming wave on the loading of a placed block revetment is small for a revetment with a leakage length equal or larger than the wave height. Oblique incoming waves can result in a considerable increase in loading when the leakage length is much smaller than the wave height and near transitions in the revetment.
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FIELD MEASUREMENTS ON PLACED BLOCK Revetments
Coastal Engineering, 1993Co-Authors: Theo Stoutjesdijk, Ben Rigter, Adam BezuijenAbstract:A report is given on a field measurement campaign on placed block Revetments. Four types of measurement are described. Typical results are presented and discussed. The entire campaign shows a consistant image of changing physical properties in the field.
