· · · Repository Hydraulic Engineering Reports

Scrap tires are proposed as a construction material for building large floating mat type breakwater devices. The Goodyear scrap tire floating breakwater assemblies are formed by securing together modular bundles of tightly interlocked scrap tires with high strength rope/cable, or special corrosion resistant steel rods. This construction procedure yields an easily installed, readily adaptable breakwater structure which has high energy absorbing capacity for normal loading conditions but which deforms and yields when subjected to overloads. The proposed designs rely on a modular bundle concept where a relatively few tires are secured together to form a small easily assemble de portable building unit which,serves as a basic building block from which giant breakwater devices can be constructed. Flotation is provided by placing a small amount of buoyant material in the crown of each tire or by filling approximately 10%) of the tires with buoyant foam. The design possibilities using scrap tire building modules are virtually limiless. Tires may be laced together to form large flat single or multiple thickness shallow mats. They may be stacked vertically in single or multiple thickness bundles like bricks in a wall to form curtain type barriers. Variutions in breakwater draft are made possible by adding modules above or below to vary the thickness and by combining constructions such as hanging a curtain on a mat structure. Also, mats with varying buoyancy may be moored on an incline for more efficient energy absorption.

Design manual for shore protection structures using old rubber tyres. With the use of old car tires one may construct floating breakwaters and reef breakwaters

An introduction to the principles and fundamentals of designing rubble mound breakwaters, led to the definition of two important white spots in designing rubble mound breakwaters. These were selected for further investigations in the present thesis. 1. Design of berm breakwaters: A generally lack of data and design formulae was identifed, but especially wave overtopping was detected as an enourmous white spot. 2. Overtopping scale effects: The motivation for the CLASH project was an expected scale effect on overtopping of rubble mound structures, leading to unsafe results obtained in a physical model. In the CLASH project comparisons of prototype and model results were performed, which confirmed the expected scale effect as more overtopping was measured in prototype. However, many possible model effects were identified, and it could not be ruled out that the differences observed were due to model effects only. Therefore, one of the main conclusions of the CLASH project was that large tests were needed, in order to obtain reliable recommendations on overtopping scale effects. These have been performed in the present project.

This brief report deals with both the pre and post implementation of the Negombo offshore breakwater scheme in west coast of Sri Lanka and is published with the collaboration of Ministry of Public works (Rijkswaterstaat), Netherlands and Lanka Hydraulic Institute, Sri Lanka, as a partial fulfilment of a MSc study carried out at International institute for Infrastructural, Hydraulic and Environmental engineering(IHE), Delft, Netherlands.

A reef breakwater is a low-crested rubble-mound breakwater without the traditional multilayer cross section. This type of breakwater, in essence, is a homogeneous pile of stone with individual stone weights similar to those used in the armour and first underlayer of conventional breakwaters. Because of their high porosity, reef breakwaters are suprisingly stable to wave attack and, at the same time, can dissipate wa ve energy effectively.

Adaptation of COBRAS VOF model for typical breakwater applications and worked out examples of water movement in and around breakwater cross sections.

The RMBFM-Project (Rubble Mound Breakwater Failure Modes) is sponsored by the Directorate General XII of the Commission of the European Communities under the Contract MAS-CT92- 0042, with the objective of contributing to the development of rational methods for the design of rubble mound breakwaters. 11 institutes from the European Union participate in the project. The paper presents an overview of the project background, the research objective, the research methodology and the research results of the project. The outcome of the project is a large amount of formulae describing important failure modes, plus development of related partial coefficients which make it possible to design according to preselected reliability levels. Due to limited space only the major activities are described.

Methode van berekenen van breakwaters met de methode van Bruun en Günbak, door gebruik te maken van het Iribarrengetal, en zo de Hudson formule te verbeteren.

In Zeeland zijn er vele havendammen die de primaire waterkering plaatselijk beschermen tegen grote golfaanval. Zelfs onder maatgevende omstandigheden zijn vele van deze dammen nog hoog genoeg om een belangrijke reducerende werking te hebben op de inkomende golven. Uiteraard kan de invloed van de golfreducerende werking van havendammen alleen in rekening gebracht worden in de veiligheidstoetsing, als de havendam en de daarop aanwezige steenzetting in stand blijven onder de maatgevende omstandigheden. Daarom is in 2002 een eenvoudige (conservatieve) toetsmethode voor havendammen ontwikkeld (Klein Breteler 2002). In dit onderzoek is een nieuwe toetsmethode ontwikkeld, op basis van resultaten van kleinschalige modelproeven in de Scheldegoot en Zsteen-berekeningen. Tijdens dit kleinschalige modelonderzoek zijn 4 havendam-configuraties getest waarbij drukken zijn gemeten op de kruin, het binnentalud en op de binnenberm. Deze gemeten drukken zijn gebruikt als invoer voor het rekenmodel Zsteen, waarmee vervolgens het stijghoogteverschil over de toplaag en de blokbeweging berekend is. GeoDelft heeft deze berekeningen uitgevoerd en heeft hiervoor Zsteen aangepast zodat het programma geschikt werd voor het doorrekenen van havendammen. De resultaten van deze Zsteen berekeningen zijn samen met de beschikbare Deltagootresultaten gebruikt voor het aanpassen van de toetsmethode. Met een theoretische beschouwing is de invloed van oneffenheden (uitstekende stenen in het taludoppervlak) bepaald. Een praktische methode voor het beoordelen van de stabiliteit van uitstekende stenen is toegevoegd aan de toetsmethode. Aansluitend zijn grootschalige verificatieproeven uitgevoerd in de Deltagoot, om de toetsmethode te kunnen controleren. Deze grootschalige proeven zijn uitgevoerd voor één configuratie met verschillende waterstand-golfhoogte combinaties. De toetsmethode blijkt goed overeen te komen met de resultaten uit het Deltagootonderzoek. In dit verslag zijn ook de resultaten opgenomen van de aanvullende studie van mei 2005 (contract ZLAO 35050044 van 22 maart 2005).

This report describes the verification of the model on dynamic stability for berm breakwaters. The model runs on a pc and is called BREAKWAT. The data received from various people allover the world contained not only berm breakwaters, but also dynamically stable low-crested structures. The title of the report was therefore changed to "Verification of BREAKWAT for berm breakwaters and low-crested structures". The calculations were performed and the report was written by Dr. J.W. van der Meer of Delft Hydraulics.

Paper describing the development of the "Hudson formula" for the stability of armor on a breakwater.

De Bouwdienst van Rijkswaterstaat heeft WL Delft Hydraulics opdracht gegeven voor het uitvoeren van 2D fysisch modelonderzoek ten behoeve van een mogelijke renovatie van de havendammen van IJmuiden. Het betreft enerzijds modelonderzoek om meer inzicht te verkrijgen in mogelijk optredende schademechanismen bij de huidige constructie (Proevenserie A) en anderzijds modelonderzoek ten behoeve van de afweging tussen drie verschillende overlagingsvarianten (Proevenserie B). De mogelijke schade mechanismen die zijn onderzocht in Proevenserie A zijn: • Het bepalen van de stabiliteit van de huidige teenconstructie. • Het meten van waterdrukken op de bodem ten behoeve van het bepalen van interne verhangen in het filtermateriaal en de kern, om mogelijke uitspoeling van zand te kunnen beoordelen. • Het meten van opwaartse krachten onder de asfaltlaag. Ten behoeve van de onderlinge afweging van overlagingsvarianten zijn drie varianten getest: 1. Variant 3b; Nieuwe toplaag bestaande uit een enkele laag hoge dichtheid kubussen, waarbij de ruimte tussen de oude toplaag en de nieuwe toplaag is uitgevuld met breuksteen. 2. Variant 4; Nieuwe toplaag bestaande uit een dubbele laag hoge dichtheid kubussen, waarbij de ruimte tussen de oude toplaag en de nieuwe toplaag is uitgevuld met breuksteen 3. Nieuwe toplaag bestaande uit een dubbele laag hoge dichtheid kubussen, waarbij de ruimte tussen de oude toplaag en de nieuwe toplaag niet is uitgevuld. Het belangrijkste doel van de modelproeven voor de overlagingsvarianten was om de stabiliteit van de toplaag, de teen en de bodembescherming van de drie varianten te vergelijken.

Background work for the "Rock Manual", verification of the wave model ENDEC on a steep 1:10 slope.

Existing design formulas for rubble-mound breakwaters under wave attack contain the wave height, H, and the slope angle, cc, as parameters of the wave characteristics (for d/H > 3.0, d being the water depth in front or the structure) and structure characteristics (incl. permeability, roughness, interlocking-, etc.) excluding the effect of wave period. When compared, they are .mostly inconsistent with their definition of stability and generally used the doubtful method of counting blocks that left their original location in the slope. A theory was therefore developed for the importance of the wave period, T , on the stability of rubble-mound breakwaters. Its validity is shown using the available laboratory data of Ref. (T) and by some experiments recently made in Norway. In connection wave run-up, run-down, breaking characteristics were summarized tan a using the Iribarren parameter.

Onderzoek naar de vanuit waterloopkundig oogpunt aanvaardbare constructies voor de nieuwe havendammen bij Hoek van Holland. Twaalf alternatieve constructies zijn globaal uitgewerkt en met elkaar vergeleken (breuksteenopties, caissons en perronwanden).

A mathematical description of sand waves along a coast and the effect of blocking structures on this coast, like groynes and breakwaters.

Research on rubble mound breakwaters when confronted with waves. The rapport covers the flow characteristics and mound stability under regular waves and under oblique wave attack. The authors find a formula for rough, permeable slopes, flow characteristics under the action of a regular wave train by a function of the type. Furthermore they conclude that the distribution of flow characteristics in sea state can be obtained on the basis of interaction curves and joint probability density function of wave heights and periods. The conclusions on the mound stability of breakwaters are: -Stability conditions of an undefined, rough, permeable slope are governed by the stability function. -The stability function depends only on Iribarren's number. -Randomness can be accounted for by using confidence bands for the stability function. -For each type of armour unit, an optimum slope of maximum stability exists. The greater the interlocking among armour units the steeper the optimum slope and the more peaked the stability maximum. -Given a rubble mound breakwater a minimum sea state exists which produces a significant failure probability. If a sea state is presented which is the same or higher than this minimum, failure of the structure is only a question of the duration of the sea state. Conclusions on the characteristics and stability of rubble mound breakwaters under oblique wave attack: -There is a dangerous lack of experimental data on the subject. -Run-up and run-down under small oblique incidence of waves (angle lower than 45 degrees) are function of Ir.cos(theta). For higher incidence angles the hypothesis is unreliable. -The stability of steep slopes under oblique wave attack is not worse than under perpendicular wave incidence. For milder slopes the opposite may be true. -The failure of probability of a rubble mound breakwater under a sea state with oblique incidence, can be calculated by taking into account the breaking limit, the interaction curve and a joint distribution of wave heights and periods.

This memorandum provides design guidance for sizing toe berm armor on breakwater and jetty trunks exposed to depth limited breaking waves whose crests approach at or near parallel to the structure

This paper reports on a laboratory investigation conducted at the United States Army Engineer Waterways experiment station, Vickburg, Mississippi, to determine criteria for the design and construction of rubble mound breakwaters. Small-scale breakwater sections are hand-constructed in a concrete wave flume 119 ft long, 5ft wide, 4 ft deep, and subjected to mechanically generated waves to determine the stability of the armor units. A general stability equation has been derived and is being used to guide the experimental program and correlate the test data. From the test data obtained important unknown functions in the general stability equation have been determined for selected breakwater and test-wave conditions, and a new breakwater stability formula has been obtained. In conjunction with the stability tests, wave run-up data are obtained for each breakwater section and wave condition tested. Also, measurements are obtained that enable the thickness and porosity of cover layers composed of different types of armor units to be determined. The new stability formula and the experimental data obtained so far have provided essential information for an improved method of designing rubble-mound breakwaters with protective cover layers composed of quarry-stone and tetrapod armor units. Tests in progress (1959) to obtain experimental data for other special shapes of cast concrete armor units (cubes, tetrahedrons, and tribars) should increase considerably the accuracy of rubble-mound breakwater design.