1,236 research outputs found
Stability of rock on slopes under wave attack: Comparison and analysis of datasets Van der Meer [1988] and Van Gent [2003]
No full textIn VAN GENT [2004] graphs were presented in which the datasets of VAN DER MEER [1988] and VAN GENT ET AL. [2003] were compared, but in this comparison a number of parameters were not correctly transformed into a comparable format. In this M.Sc. thesis after an extensive analysis to the datasets all parameters of the datasets of Van der Meer were transformed into the same format as the parameters used by Van Gent. In the same way the dataset of THOMPSON & SHUTTLER [1975], which formed the basis of the work of Van der Meer, was treated. The inclusion of correction factors for the effects of stone roundness from LATHAM ET AL. [1988] gave remarkable effects on a certain part of the dataset of Van der Meer which showed more damage than average. After this still differences could be seen between the datasets of Van der Meer and Van Gent. Using the statistical T-test these differences are approved. Explanations for the differences found between the datasets of Van der Meer and Van Gent can be found in the fact that most of the tests of Van Gent. were done with shallow foreshores where Van der Meer did most tests with deep water conditions. Tests by a number of M.Sc. students at Delft University of Technology showed that tests with identical spectra, but with different foreshore slope angles show different damage patterns. In the dataset of Van Gent also the 1:30 foreshore slopes on average show more damage than the 1:100 slopes. In further research the influence of the foreshore should be incorporated in the stability formulae by a foreshore Iribarren parameter. Also a detailed investigation to the effects of wave breaking on shallow foreshores is needed. For this the complete dataset of Van Gent needs to be available and accessible.Hydraulic EngineeringCivil Engineering and Geoscience
Stabiliteit breuksteen bij ondiepe voorlanden
No full textBij WL is onderzoek uitgevoerd naar stabiliteit van breukstenen taluds bij (zeer) ondiepe voorlanden. De paper voor Coastal Structures 2003 "Stability of rock slopes with shallow foreshores" door van Gent, Smale en Kuiper is een samenvatting van het werk. Hierin wordt voorgesteld een andere periodemaat te nemen dan in de van der Meer formule en daarbij de coëfficiënten opnieuw te kalibreren. Uiteindelijk wordt een nieuwe formule voorgesteld waarin de periode invloed volledig is verdwenen
Doorbraakvrije dijken: Opzet doorbraakvrije zeedijken en voorlopige conclusies sterkte binnentaluds bij golfoverslag
No full textIn het kader van WV21 wordt door Deltares en een werkgroep gekeken naar doorbraakvrije dijken. Er wordt gekeken naar de definitie van doorbraakvrij en daarnaast naar hoe doorbraakvrije dijken er zouden moeten uitzien ten opzichte van de huidige dijken. In dit kader is aan Van der Meer Consulting gevraagd specifiek uitwerking te geven aan doorbraakvrije zee- en meerdijken en is gevraagd voorlopige conclusies op te stellen naar aanleiding van de proeven met de golfoverslagsimulator omtrent de sterkte van binnentaluds van dijken tegen golfoverslag. Deze uitwerking en het maken van voorlopige conclusies is gedaan door meerdere personen/bedrijven hierbij te betrekken, namelijk de projectgroep voor de proeven bij de Boonweg in Friesland en de proeven in Zeeland (Deltares zelf, Infram, Royal Haskoning en Alterra) en Infram ten aanzien van doorbraakvrije zeedijken. Vanuit observaties van de golfoverslagproeven (zie appendix 1 voor een fotorapportage met beschrijving) is één hoofdconclusie met betrekking tot doorbraakvrije dijken naar voren gekomen. Gesteld wordt dat het aannemelijk lijkt dat een binnentalud van klei met gras bij een overslag van 30 l/s per m of minder nooit door erosie zal bezwijken. Dit betekent dat in veel extremere omstandigheden dan de huidige maatgevende belasting, een huidige zee- of meerdijk niet door overslag zal bezwijken. Om het faalmechanisme infiltratie door golfoverslag en afschuiven van het binnentalud uit te sluiten, dient een doorbraakvrije zee- of meerdijk een binnentalud van 1:3 te hebben. Als kostenalternatief kan ook gekeken worden naar een binnentalud van 1:5. Omdat de huidige zee- en meerdijken al voor hoge stormvloeden en hoge golven zijn of worden ontworpen, lijkt het relatief gezien geen grote ingreep om deze dijken bestand te maken voor een veel zwaardere storm met een veel kleinere kans van voorkomen. En deze dijk zodoende doorbraakvrij te maken. Als meer golfoverslag wordt toegestaan in zeer extreme omstandigheden (tot ver boven de huidige maatgevende omstandigheden), en wanneer een zee- of meerdijk moet worden verbeterd, dan is het niet een grote stap om deze dijk, ook voor de komende 50 jaar, doorbraakvrij te maken. Bekledingen moeten dan iets dikker worden dan wat nu volgt uit het huidige ontwerpproces en ze moeten iets hoger op het talud worden aangebracht en de dijk moet mogelijk iets hoger
The effect of the through-the-thickness compressive stress on mode II interlaminar fracture toughness
No full textThe effect of through-the-thickness compressive stress on the mode II interlaminar fracture toughness is investigated experimentally and replicated numerically. The modified Transverse Crack Tensile specimen recently proposed by the authors is used, together with an experimental device designed to apply a constant transverse compressive stress on the surface of the specimen. Experiments are conducted using IM7/8552 specimens for different compressive stresses, ranging from 0 to 100 MPa, covering all the practical applications commonly encountered in the aeronautical industry (e.g., tightened filled holes or bolted joints). It is shown that the mode II interlaminar fracture toughness increases with the applied compressive through-the-thickness stress. Finally, experiments are replicated using appropriate numerical models based on cohesive elements that take into account frictional effects. A good agreement between numerical predictions and experiments is found.</p
Van de grond af opgebouwd
No full textBundeling van de lezingen ter gelegenheid van de 80e verjaardag van prof. Agema, naast de lezingen staan er twee interviews met prof. Agema in deze publicatie. De bijdragen van de overige sprekers zijn: Rijkswaterstaat: de (te) grote opdrachtgever in de GWW (Struik), De fundamenten onder het ontwerp (vd Meer), Buitenland en waterbouw (Zanetti), Uitvoeren met verstand (Beerda), Techniek en grote projecten (Korf)Hydraulic EngineeringCivil Engineering and Geoscience
Guidance on erosion resistance of inner slopes of dikes from 3 years of testing with the Wave Overtopping Simulator
No full textThe Wave Overtopping Simulator was developed in 2006 and destructive tests have been performed in February and March of 2007, 2008 and 2009 and will probably be continued in 2010. The tests show the behaviour of various inner slopes of dikes, embankments or levees under simulation of wave overtopping, up to a mean overtopping discharge of 125 l/s per m. In 2010 a Technical Report on strength of inner slopes of dikes against wave overtopping will be written, leading to new guidelines for the required five-yearly safety assessment of flood defence assets in the Netherlands. This paper will give a mid-term review and first guidance, based on 3 years of destructive testing. Till summer 2009 15 sections of dikes at 5 different locations in the Netherlands have been tested. The paper will give guidance to practical engineers, based on observations and analysis from all the testing so far. It also discusses the possible modifications in safety assessment.SB
Taluds van losgestorte materialen: Golfneerloop op statisch stabiele stortsteen taluds onder golfaanval
No full textIn dit verslag worden neerloopmetingen gepresenteerd en geanalyseerd welke zijn verkregen uit onderzoeken naar de statische stabiliteit van stortsteen taluds onder golfaanval. De analyse van deze proeven heeft geleid tot de relatie voor de relatieve neerloop die door 2% van de neerlopen wordt overschreden. Deze empirische relatie wordt beschreven aan de hand van dimensieloze parameters, welke zijn afgeleid van de in de onderzoeken gevarieerde grootheden. De relatieve neerloop wordt belnvloed door de volgende dimensieloze parameters : \u95 golfsteilheid (sm) \u95 taludhelling (cot alpha) \u95 doorlatendheid van de constructie (P) \u95 spectrumvorm (K) \u95 relatieve waterdiepte (h/Hs)Applied Geophysics and PetrophysicsHydraulic EngineeringCivil Engineering and Geoscience
Design of the US Wave Overtopping Simulator
No full textThe US Wave Overtopping Simulator has to simulate overtopping discharges up to 2 cfs/s/ft for wave conditions of respectively 8 ft with a peak period of 14 s and 3 ft with a period of 6 s. This requires a Simulator which is in size about three times larger than the existing Dutch one. This report describes the theory of waves overtopping the crest of a levee, the design of the Simulator, how to operate it and possible ways to measure hydraulics during testing. We know a lot about wave overtopping over levees, but still there are discrepancies between various formulae. First the existing theory is given about wave overtopping discharge and individual wave overtopping volumes. This leads to the distributions of wave overtopping volumes that have to be simulated by the Simulator. Then flow velocities, flow depths and flow times or durations of overtopping wave volumes at the crest of a levee have been discussed, including re-analysis of existing work and some recent research. The conclusion is that using the equations in an integration, to calculate the wave overtopping volume, the volumes are much too large, indicating that at least flow depth andflow time predictions are too large. For this reason the Simulator will mainly be based on flow velocity and the given peak periods of the waves. Good experience is available with Simulators up to a size of about 6 m3/m width. The majority of all overtopping wave volumes will be limited to this size. It is for this reason that the US Simulator has been designed with an inner Simulator, comparable to the existing sizes, and an outer Simulator, giving the maximum capacity of 16 m3/m. The outer Simulator will only be used for the very large overtopping wave volumes. The mechanical design has been described and this design has been discussed during a visit to CSU, in order to start fabrication of the Simulator. The Dutch test set-ups at various locations have been described with their improvements every consecutive year. The operation of the Simulator by a steering file and PLC has been given, first by description of the Dutch Simulator and then by possible modifications and improvements for the US Simulator. Finally, experiences to measure flow depth and front velocity of overtopping waves have been described and possible ways of improvements, which will be performed in the Netherlands and tested in February/March 2010. If successful, these kind of measurements can also be developed at CSU
The effect of through-thickness compressive stress on mode II interlaminar fracture toughness
No full textThe effect of through-thickness compressive stress on mode II interlaminar fracture toughness is investigated experimentally and replicated numerically. The modified Transverse Crack Tensile specimen recently proposed by the authors is used, together with an experimental device designed to apply a constant transverse compressive stress on the surface of the specimen. Experiments are conducted using IM7/8552 specimens for different compressive stresses, ranging from 0 to 100 MPa, covering all the practical applications commonly encountered in the aeronautical industry (e.g., tightened filled holes or bolted joints). It is shown that mode II interlaminar fracture toughness increases with the applied compressive through-thickness stress. Finally, experiments are replicated using appropriate numerical models based on cohesive elements that take into account frictional effects. A good agreement between numerical predictions and experiments is found.</p
The wave run-up simulator: Idea, necessity, theoretical background and design
No full textThe idea of the Wave Run-up Simulator is based on the experiences with the Wave Overtopping Simulator. It is possible to simulate wave tongues overtopping a dike crest in reality. It must also be possible to simulate waves in the run-up and run-down zone of the seaward slope. This is the zone after waves have broken and when they rush-up the slope. The present report describes the idea of the Wave Run-up Simulator, why it is useful to develop the machine, to perform research with it and to develop a prediction method for slope strength. In fact, a prediction method can already be developed from the cumulative overload method, which was developed on the basis of results with the Wave Overtopping Simulator. It also means that tests on the seaward slope will be done for validation purposes only. The second part of the report describes in detail what is known about the movement of waves in this run-up zone and what actually the Wave Run-up Simulator has to simulat
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