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International Journal on Public Works, Ports & Waterways DevelopmentsNumber 93 • December 2003

International Association of Dredging Companies

Terra et Aqua – Number 93 – December 2003

Terra et Aqua is published quarterly by the IADC, The International Association of Dredging Companies.

The journal is available on request to individuals or organisations with a professional interest in the

development of ports and waterways, and in particular, the associated dredging work.

The name Terra et Aqua is a registered trademark.

Editor

Marsha R. Cohen

Editorial Advisory Committee

H.L.H. Smink H.W.J. Poiesz, Chairman A.G.M. Groothuizen

H.A.J. Fiers C.P.I.M. Dolmans P.G. Roland

H. de Vlieger R. Vidal Martin C. Meyvaert

IADC Board of Directors

R. van Gelder, President T. Tawara, Vice President C. van Meerbeeck, Treasurer

P.G. Roland M. Montevecchi G. Vandewalle

O.F. Verkerke

Please address inquiries to the editor.

Articles in Terra et Aqua do not necessarily reflect the opinion of the IADC Board or of individual members.

© 2003 IADC, The Netherlands

All rights reserved. Electronic storage, reprinting or abstracting of the contents is allowed for

non-commercial purposes with permission of the publisher.

ISSN 0376-6411

Typesetting and printing by Opmeer Drukkerij bv, The Hague, The Netherlands.

Cover:Overview of an embankment disposal area of the High Speed Railway Line (HSL) along the auto route inThe Netherlands going to the Belgium border (see page 3.)

IADC

Constantijn Dolmans, Secretary General

Duinweg 21

2585 JV The Hague, The Netherlands

Tel. +31 (70) 352 3334, Fax +31 (70) 351 2654

E-mail: [email protected]

http://www.iadc-dredging.com International Association of Dredging Companies


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CO N T E N T S

2 Editorial

3 Recent Innovations in the Design and Construction of Railway Embankments

Chris Dykstra and Art Nooy van der Kolff

Despite adverse geotechnical conditions, stable sand embankments for the Betuwe Routeand the HSL train have been achieved by using new accelerated consolidation techniques.

10 “Bon Voyage, Mr. Hamburger…”

A fond farewell to the Secretary General of the IADC who has left his post to embark on anew adventure.

11 Numerical Simulation of the Development of Density Waves in a Long Pipelineand the Dynamic System Behaviour

Sape A. Miedema, Lu Zhihua and Vaclav Matousek

To realise a stable dredging process, line velocity should not vary too much. A simplifiedtwo-dimensional model is used to demonstrate how to control line velocity by varying therevolutions of the dredge pumps.

24 “The Suez Canal — Camels, Sand and Water”

An exhibition at the National Dredging Museum in The Netherlands provides insight intothe magnitude of the canal’s construction.

26 Books/Periodicals Reviewed

The Proceedings of two conferences this summer (one in Spain, one in Chicago) offer goodreading as does a new book on the Suez Canal.

29 Seminars/Conferences/Events

2004 is starting with conferences in India, Malaysia and Singapore, and Hamburg,Germany is gearing up to host the WODCON.


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EDITORIAL

In this last issue of 2003, it is interesting to look back and see where we havebeen this past year. Remarkably, we have celebrated the existence of two majorwater works: the Panama Canal in our March number, and the Suez in this issue.As well we have commemorated the 1953 flood disaster in The Netherlands,which led to the construction of the Delta Works. This project in the West, whichspanned three decades, and the major land reclamation developments in the East– in Hong Kong and Singapore – in the 1990s mark the beginning of the moderndredging age with its jumbo dredgers and environmental assessments anddedicated equipment.

The twentieth century was an era of incredible advances and inventions in therealm of dredging. The twenty-first promises to continue this with new mega-projects, such as the Palm Islands in Dubai, UAE, which herald yet another age of large infrastructure advancements. Certainly the construction and dredgingprojects in Dubai will go on for quite some time, as will the major developments inEurope and Asia, and will offer many other interesting articles for future Terras.

In addition, our attention has focused on environmental values, public aware-ness, and communication between the industry and stakeholders. These too aresubjects which are worthy of our energies and important to the successful growthof the dredging industry. In this issue of Terra, important scientific studies that arethe basis of dredging technology are highlighted. These include soil mechanics for creating stable sand embankments, and the role of numerical modelling inoptimising slurry transport over long distances by regulating the pump/pipelinedesigns. Innovative approaches as those described here keep the private dredgingcontractors in the forefront of the industry.

Also looking forward, there have been two recent IADC Awards to youngauthors, one at COPEDEC in Sri Lanka, and the other at the CEDA DredgingDays just held in Amsterdam in November. Both these award papers will appearin the coming issues of Terra. In July 2004 WEDA will one again hold its annualmeeting in Orlando, Florida. And, promising to be bigger and better than ever, the WODCON will take place in late September. Held only once in three years, in 2004 the city and port of Hamburg, Germany has the honour of hosting thiselaborate event under the organisational auspices of CEDA. Clearly as theNew Year begins, dredging opportunities are as challenging and exciting as ever.

Robert van GelderPresident, IADC Board of Directors

Abstract

Two major railway lines, the Betuwe Route (BR) andthe High Speed Railway Line (HSL), are currently underconstruction in The Netherlands. Stringent requirementswith respect to the construction time and the residualsettlements of the future embankments have stimulatednew developments in the field of soil mechanics andconstruction technology. Given the limited constructiontime and the adverse geotechnical conditions in thewestern part of the country initial designs tended tofocus on the (virtual) elimination of settlements. This was to be achieved by various new systems, all based on the principle of stiff elements transferringthe bearing loads to deeper competent strata. High costs of such systems and uncertain performance,however, urged designers to reconsider the options.

In the case of the Betuwe Route this resulted in atraditional embankment design supplemented withspecial measures to accelerate the consolidationprocess and/or increase the strength of the subsoil.This so-called traditional-plus approach proved to be the most cost-effective solution to meet the contractrequirements in terms of both construction time andresidual settlements.

For the HSL, dynamic loads as a result of the highvelocity of the trains prompted a design comprisingconcrete slabs founded on piles. Where these slabsrise above the original ground level, embankments ofsand are required between the slabs and the groundsurface to reduce bending moments in the piles. To avoid large settlements of these embankments theoriginal design included (partial) replacement of thecompressible strata. However, further optimisation of the design resulted in the use of accelerated consolidation techniques to enforce full settlementbefore driving the piles.

Both of these projects have demonstrated that stablesand embankments can be constructed in a relativelyshort period of time even in areas with underlying verycompressible soils.

Recent Innovations in the Design and Construction of Railway Embankments

C.J. Dykstra and A.H. Nooy van der Kolff


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Chris Dykstra graduated from DelftUniversity (Mining) in 1979 and hasbeen working ever since for Boskalis:as a research engineer, dredging engineer, site engineer on variousprojects abroad and since 1996 assenior engineer with Boskalis’ engineering company, Hydronamic.He was closely involved with theBetuwe Route (BR1/2) project fromtender to construction stage, in the roleof team leader for geotechnicalembankment design.

Chris Dykstra

Art Nooy van der Kolff is presentlyworking with Boskalis Westminster as a senior geotechnical engineer in the Estimating Department. Aftergraduating from Delft University inEngineering Geology, he joinedGeoDelft (formerly known as theDelft Soil Mechanics Laboratory) andfor more than 10 years worked there asa geotechnical engineer/engineeringgeologist on projects all over the world.He is currently involved in thedevelopment of the BeauDrain system.

Art Nooy van der Kolff

Introduction

The geological setting of The Netherlands is determinedby its position on the edge of the North Sea SedimentaryBasin. With Tertiary and older rocks outcropping nearits eastern and southern borders the thickness of thesequences of unconsolidated Quaternary depositsincreases towards the west and north reaching amaximum thickness of 500 m in the NW. In particularin the western part of the country positioned in thedelta of the Rhine, Meuse and Scheldt the Holocenestrata comprise soft, highly compressible clays, organic clays and peats of alluvial and marine origin,occasionally intersected by more sandy strata. Atdepths typically varying between 5 m and 15 m belowsurface Pleistocene sands underlie these deposits.

BETUWE ROUTE

Over the last five years, construction has commenced onseveral large infrastructural projects in The Netherlands.One of these is the Betuwe Route, a 160 km longelectric freight railway line from the Port of Rotterdam tothe German border. The Betuwe Route was tenderedin sections of which the 22 km section Sliedrecht-Gorinchem, also known as BR1/2, is further describedin this paper (Figure 1).

The surficial geology is relatively uniform. The shallowsubsurface consists of highly compressible Holocenedeposits overlying dense Pleistocene sands. The Holocene deposits essentially comprise a thincover of agricultural soil (clay) overlying peat and clays.The peat is known locally as Holland Peat while theclays are part of the Gorkum Formation. The Holoceneunits are generally soft to very soft with undrainedshear strengths in the range of 5-15 kPa. The thicknessof the Holocene varies from about 10 m in the westernpart of the BR1/2 section to 8 m in the eastern part.

This section was considered a high-risk section, not in the least because of the combination of poor soilconditions with a tight contractual time frame and strictdirectives for allowable residual settlement. As a simple solution for all project risks was notobvious, the Owner, ProRail, tendered this section as a Design, Construct & Maintenance contract. After a pre-selection phase, five consortia were askedto prepare detailed bids. Only one consortium, HBSC (Heijmans, Boskalis, Structon, CFE), cared tobase its design on a more or less traditional approachusing a sand fill embankment and wick drains.

HBSC’s design was much influenced by an innovativeapproach to the geotechnical design aspects. The risks associated with this approach were perceivedto be high but ultimately a consensus was found byadopting an Alliance as contractual form.

This allowed better allocation and control of risk andprovided more incentive (for all contractual parties) toidentify and realise optimisations. Many of the optimi-sations were directly related to geotechnical aspects.Some key components of the geotechnical design aredescribed below.

Overall parameter setThe results of an extensive suite of field and laboratorytests (see Table I) were included with the tender docu-ments. A geological interpretation was also included, in the form of a longitudinal profile.

Table I. Soil investigation.

Test Type Number

Dutch Cone 658Begeman 66 mm Borehole 51Begeman 29 mm Borehole 94Laboratory Triaxial Tests 201


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Figure 1. Sliedrecht-Gorinchem section of the Betuwe Route.

In practice, very few stability problems occurred. The problems that did occur were not a result of thisapproach but always related to an unrecognised localfeature. The impact of embankment stability problemson cost and schedule were virtually negligible.

Wick drainsDuring construction, loading the embankments withsand leads to the development of excess pore waterpressures in the subsurface soils. These excess porepressures must be allowed to (partially) dissipatebefore additional lifts of sand can be placed. The rate ofconsolidation thus poses a restraint on the attainablerate of embankment construction. Typical for thesesoils is the combination of a high compressibility with avery low permeability, leading to an extremely lowcoefficient of consolidation.

It will then be no surprise that, given the contractualspecifications with regard to allowable constructiontime, it was decided to maximise the consolidation rateby installing vertical wick drains (Figure 2). Drains wereinstalled at a center-to-center spacing of about 1m.Initially serious doubts were raised concerning thevalidity of the existing design rules (e.g. Kjellman) forsuch close drain spacing. The results of field monitoringwith settlement beacons and water pressure meters (the “observational method“) showed that the drainsperformed at least as well as predicted. Thus, based on“observational method“, these concerns were shownto be unfounded.

GeotextileSand was generally placed in lifts of 1-1.5 metres thick.Even with these limited lift heights stability problems

According to the provisional geotechnical interpretationsupplied with the documents the route was to bedivided into a number of geotechnically distinct sub-sections. Suggested values of geotechnical parameters(such as shear strength) were supplied for each sub-section. The number of samples and tests variedconsiderably from section to section. This implied thatthe statistical confidence level with regard to parametervalues also varied significantly from section to section.The values of some parameters also fluctuated stronglyfrom section to section (for a given soil type). In somecases, the given parameter set was such that it wasvirtually impossible to design a traditional sand embank-ment that met all the contractual criteria, notably withregard to allowable construction time.

However, statistical analysis of the available test datashowed that there was in fact no reason to assumesignificant spatial correlation of parameter values. In other words, for a given soil type, the geotechnicalproperties did not vary from location to location. Thus for each soil type only one overall set of parameterswas required for the whole route. This simplificationconsiderably reduced the need for additional geotechnical fieldwork. By combining all the test data itwas also much more evident which test results werenon-representative (erroneous). Also, by decreasing thenumber of design variables, the potential for designerrors and discrepancies (from section to section) wasgreatly reduced.

All the embankment design was based on the overallparameter set. This choice has been further validatedempirically; embankment construction has beencompleted and to date there is no evidence suggestingthat local parameters should have been used.

Minimum shear strengthIn the Netherlands, slope stability is traditionally deter-mined with a Bishop method, using drained shearstrength parameters (c' and �’). This method was infact specified in the contract. Triaxial Dutch Cell testsshowed that the cohesion value for these soils wasgenerally very low (ca. 1-3 kPa). At low effective stresslevels (e.g. in the toe of an embankment and beyond),the shear strength predicted along a failure plane isthen very low. Calculations with this approach suggestedthat even an initial sand lift of only 1 m thickness wouldlead to slope failures, especially if the embankment toewas adjacent to a drainage ditch.

This clearly did not correspond to empirical observationsthat lifts of 1.5 m and more were quite safe. Slopestability calculations with minimum (undrained) shearstrengths (cu about 5 kPa) yielded results that camemuch closer to actual field practice. Ultimately anapproach was chosen which combined a minimumshear strength at low stress levels with drained shearstrength parameters at higher stress levels.


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Figure 2. The placement of vertical drains.

were anticipated so in fact for most of the embankmenta geotextile was placed on the original ground prior tosand placement. Since the wick drains were onlyinstalled after a floor of sand had been placed, thismeant that the drains perforated the geotextile.

A damage factor based on the drain spacing and gridorientation was included in the geotextile design analysis. In practice very few stability problemsoccurred. To our knowledge this is the first time thatgeotextile was used in the Netherlands in this mannerand at this scale (Figure 3).

Settlement monitoringIn The Netherlands, creep has long been recognised ashaving a major influence on settlement. The traditionalapproach to settlement calculations is based on theKoppejan equation.

This model displays a number of shortcomings. The first is that the rate of creep is independent of thedevelopment of effective stress (i.e. consolidation). In addition, the creep increases not only with time butalso with the magnitude of the total stress increment.

The latter is contrary to most international practice.

In the case of stepped load increments, it is quitearbitrarily assumed that the total creep can be calculatedby adding the creep components of each load stepseparately (“superposition principle“). Lastly, the effectof a temporary surcharge (loading followed by unloading)is by no means well defined in this model.

All of these aspects are unsatisfactory. As moreemphasis is placed on reducing post-constructionsettlement it is increasingly important to have apredictive model, which can be used with anacceptable degree of confidence. After dueconsideration, the Koppejan approach was abandonedand an in-house model based largely on Yin andGraham (Yin et al. 1999) was developed. It must sufficehere to say that this model uses the concept ofequivalent creep time and isotachs (lines of constantcreep strain rate). The compression coefficients usedare based on common international practice (i.e. cc, c�

etc). Both stepped loading and unloading conditions areclearly formulated, including an unambiguous definitionof creep time.

Settlement beacons were placed at 50-metre intervalsalong the axis of the embankment. The Asaoka method(Dykstra et al., 2001) proved to be a useful tool forestimating the actual consolidation coefficient from thefield settlement data. Very good fits of the recordedsettlements were generally obtained with the isotachmodel. Based on the derived fit parameters it waspossible to predict the post-construction settlement ateach beacon location. The model also became animportant tool to establish the required finished levelsduring construction (e.g. prior to placing the ballast bed).

ConstructionSand for embankment construction was brought to thesite by barges and unloaded with a barge-unloadingdredger. The sand was discharged either directly intothe embankment (Figure 4) or into a depot area fromwhere it was trucked to the route (Figure 5). A total of roughly 2.5 million m3 of sand was placed, much of which was “Sea Sand“ won in the North Sea. The North Sea sand was desalinated during transportfrom the winning area to the site. Desalination was soeffective that the environmental restrictions concerningthe maximum salinity of the placed sand were met.

HSL (HIGH SPEED RAILWAY LINE)

In 1997 the Dutch government took the decision toconstruct a high speed railway line linking up with the European network of high speed railway lines.Construction of the first line running from the Belgiumborder near Antwerp via Rotterdam to Amsterdamstarted in 2000. Most of this railway line passesthrough the western part of the country with itsadverse geotechnical conditions.


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Figure 3. Lining the embankment with geotextile placement.

the Dutch Ministry of Public Works initiated a full scaletrial of various new techniques to reduce or eliminatesettlements (‘No-Recess’ or ‘New Options for Rapidand Easy Construction of Embankments on Soft Soil’)in areas with poor subsoil conditions.

Embankments founded on stabilised columns,stabilised walls, geotextile-encased sand columns andslender cast in-situ piles were tested by subjectingthem to static and dynamic loads. All systems werebased on the same principle of transferring the loads bystiff elements to the competent sandy strata of the Pleistocene occurring at a depth of approx. 5-15 mbelow ground level. None of the tested systems,

As with the Betuwe Route, the construction wastendered in sections. The contract of the most northernsection (HSL1) of approximately 16 kilometresbetween the villages of Hoofddorp and Leiderdorp wasawarded to a joint venture of five Dutch contractorsknown as Bouwcombinatie Hollandse Meren. The contract included not only the foundation of thehigh speed railway line with its bridges and viaducts,but also widening of a part of one of the busiest high-ways in The Netherlands: the A4 between Amsterdamand The Hague. This highway runs partly parallel to thenew railway line and crosses it. Both the railway lineand the highway also have to cross two waterways inthis section. Traffic on the highway should not beinterrupted or hampered.

Geotechnical conditions and challengesPoor geotechnical conditions along the proposed align-ment comprised below a thin cover of agricultural soilfrom top to bottom: soft, often clayey peat, soft to verysoft organic clay, soft to very soft silty clay, soft to firmpeat and finally medium dense Pleistocene sand.

Low to very low shear strengths of the cohesive strataintroduced potential stability problems, while highcompressibility of these deposits could cause largesettlements when loaded.As the proposed railway line transverses various poldersthese conditions could vary considerably. High ground-water tables and serious limitations to the allowableimpact of construction methods on the groundwaterregime of the polders further complicated the situation.

Geotechnical designStrict requirements with respect to the (long-term)settlements of the high speed railway line necessitateda careful design process. Prior to the construction,


Figure 4. Sand being hydraulically discharged directly into the

embankment.

Figure 5. An embankment area being filled by trucks.

however, produced satisfactory results and it wasdecided to apply a system of concrete slabs foundedon conventional driven concrete piles.

Although generally running just above ground level, the line is elevated over existing infrastructure (roads,waterways and other railway lines). To avoid excessivebending moments in the piles as a result of brakingforces of the high-speed train the design of theapproaches to the abutments of bridges and viaductsincluded earth embankments between the concreteslab and existing ground level. The construction ofthese embankments introduced a number of geo-technical problems in terms of stability and long-termsettlements. Tight planning did not allow enough timefor conventional consolidation methods of the highlycompressible, cohesive subsoil. In addition, excessivelong-term deformations (creep) could introduceunacceptable bending moments in the piles carryingthe concrete slabs.

In the final design it was foreseen to remove 3-4 m ofhighly compressible clays and peat and replace it withsand. Reducing the thickness of the compressiblelayers increased stability and reduced the (residual)settlements (Figure 6).

In the area where the railway line and the highway

run parallel, excavation of the cohesive sedimentsimmediately adjacent to the high embankment of theexisting highway was considered to be too risky.Instead it was decided to apply alternative techniquesto accelerate the consolidation process, not onlyincreasing the shear strength of the cohesive strata,but also reducing the long-term settlements (creep).One of these techniques was a new vacuum consolida-tion system, the BeauDrain system, recently developedby Boskalis Westminster.

BeauDrain systemThe BeauDrain system combines the well-establishedtechnique of vacuum consolidation with an innovativeinstallation procedure illustrated in Figure 7. Through aspecially designed plough that is pulled by a hydrauliccrane, prefabricated vertical (wick) drains are installedand cut at predefined depths below ground level. While the plough is moving a horizontal collection drainis placed at a depth of approx. 3 m below groundsurface and is connected to the vertical drain. Before itleaves the plough, the horizontal drain is also coveredby an impervious geomembrane in order to ensure aproper sealing between the horizontal drain and theatmospheric conditions.

The whole system, which is usually referred to as adrainage curtain, consists of a row of vertical drains,

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Figure 6. An overview of the embankment disposal area of the HSL.

horizontal drains and the existing technique of vacuumconsolidation.

These projects demonstrate that improvements inembankment design and construction do not necessarilyrequire completely new, revolutionary ideas, but canwell consist of innovative use of existing knowledgeand techniques.

References

Dykstra, C.J. and Joling, A.G. (2001).“Praktijkwaarde consolidatiecoefficient bepaald met Asaoka

methode“. Geotechniek, vol. 7, nr.2 (in Dutch).

Kjellman, W. (1948).“Accelerating consolidation of fine grained soils by means of

card board“. Proceedings 2nd ICSM, vol.2, p.1201-1226.

Yin, J.H., and Graham, J. (1999).“Elastic viscoplastic modelling of time-dependent stress-strain

behaviour of soils“. Canadian Geotechnical Journal, 36: 736-745.

a horizontal drain and seal. It is placed in a single passof the plough. After passage of the plough thecompressible soil usually closes in on itself above thehorizontal drain creating a natural seal that augmentsthe geomembrane. The total system consists of anumber of drainage curtains connected to vacuumpumps.

The net effect of the introduction of a vacuum in the subsoil is an additional atmospheric surcharge,which will ensure an early attainment of the requiredsettlement, and an increased shear strength favouringthe stability (accelerated loading schemes, steeperslopes in areas with limited space).

Embankment constructionAlthough most of the embankments could beconstructed using the traditional method of replacingpart of the cohesive strata by sand, a number of criticalsections are being raised using this new method toaccelerate consolidation. Not only does it savesurcharge sand, it also allows for a reducedconstruction time and has eliminated the risk of afailure of the embankment of the existing highway.

The degree of consolidation at any time duringconstruction and predictions of post-constructionsettlements are based on fits of the actually measuredsettlements using the same in-house developedsettlement model discussed before. The consolidationdegree is used to monitor the stability of the variouslifts, while the prediction of post-constructionsettlements determines the moment the residualsettlements meet the settlement criteria.

Conclusion

A 22 kilometre embankment section of the BetuweRoute freight railway line has been designed and builtby an alliance of ProRail (Dutch railway infra manager)and HBSC (a combination of four large Dutch andBelgium contractors) in an area of highly compressiblesoils. The contractual form of an alliance was chosen tomaximise synergy between the various contractualparties. In November 2003, four years after the start ofthe alliance, the project will be completed within thecontractual time frame and well within the originalproject budget. The contractor’s geotechnical designwas especially a major contribution to the success ofthe project.

Like the Betuwe Route, the HSL is being constructed inan area with very poor subsoil conditions. The potentialstability problems of the existing embankment of oneof the busiest highways in The Netherlands runningimmediately adjacent to the new railway line have beensolved by locally using the BeauDrain system, a new,innovative combination of conventional vertical and


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Figure 7. BeauDrain system, combines the well-established

technique of vacuum consolidation with a newly designed

plough pulled by a hydraulic crane.

“It’s been more than a decade since I first came on the scene at the International Association of DredgingCompanies headquartered in The Hague,” recalls Mr. Peter Hamburger, who recently stepped down asIADC’s Secretary General, “and there have been quitesome changes in the dredging world in that decade. As the umbrella organisation for the private dredgingindustry, in these years of expanding markets and jointventures, the role of IADC has become continuallybroader. As a result, I felt it was necessary at this timeto improve the profile of the industry towards theoutside world. This meant reaching out to other maritime institutions, such as the IMO, CEDA, WEDA,IAPH, PIANC, as well as FIDIC, and also to stakeholdersand other third parties”.

“Amongst the most outstanding accomplishments ofthe last years has been the attention spent to environ-mental issues and public awareness,” Mr. Hamburgercontinues. “Dredging projects have an impact on thedaily lives of people. Therefore the public has a right toknow what’s going on. But they need to know that thisimpact is positive, that dredging is a force for economicand social development. With CEDA, we published aseven volume series of books on The Environmental

Aspects of Dredging. Working with PIANC, we co-sponsored the Beneficial Uses of Dredged Materials.In cooperation with IAPH, we revised, and are presentlyupdating, Dredging for Development. In coordinationwith OPL, the initiative to publish Dredgers of theWorld was undertaken, and the fourth revised editionhas recently appeared. More and more we are invitedto participate at major trade shows, and the IADCAward for the best paper written by a younger author— to encourage young people to enter the industry —has grown from one award per year to several awards”.

“Other publications like Dredging the Facts andDredging the Environmental Facts were developedwith a group of partner organisations, as waswww.dredgeline.net, a new Internet bibliography forthe industry. Another achievement is the weeklongIADC Seminar on Dredging & Reclamation whichstarted at the UNESCO-IHE in Delft, the Netherlandssome eleven years ago, and since then has beenpresented 23 times in Singapore, Buenos Aires, Egyptand this year in Dubai. It’s been a remarkable anddynamic voyage working at the IADC”.

But, as with most journeys, the ship reaches its portand accordingly, “it was time to venture out intouncharted waters, and start on an exciting ‘maidenvoyage’ with new ideas for the maritime industry,”says Hamburger. “My management company inAmsterdam will provide that opportunity”. Slightlysentimentally, Hamburger remarks, “Turning over thereins to Constantijn Dolmans is a natural transition. He has been my right-hand man at IADC for the lastfive years and we’ve enjoyed a great working relation-ship. With a degree in law and public administration,Constantijn has contributed enormously to IADCprojects such as adapting the FIDIC’s StandardContract Conditions to the dredging industry’s needs,assembling statistics about the fleet of IADC members,verifying dredging accuracies, and a number of publicrelations activities including the new IADC website”.

With one last look back at his farewell party in September, where over 100 people came to wish him luck, Mr. Hamburger is now looking forward. “We will keep close contact with Peter,” Mr. Dolmanssaid, as they stood side by side. “He set an importantnew course at the IADC, and we look forward to build-ing on the expertise and ideas he developed over theyears. We all wish him a ‘bon voyage’ as he heads outfor new ports and new challenges.”


“Bon Voyage, Mr. Hamburger……”

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Peter Hamburger (right) with Constantijn Dolmans in front of

the IADC Secretariat in the Hague.

Abstract

Slurry transport is used in dredging and mining totransport solid/liquid mixtures over a long distance andvery frequently multiple pumps are utilised. To describethe processes involved, very often a steady stateapproach is used. A steady state process, however,requires a constant density and solids properties in thesystem and thus at the suction mouth. In practice it isknown that the solids properties and the densitychange with respect to time. The density wavesgenerated at the inlet of the system tend to transformtheir shape while moving along a pipeline. Undersuitable conditions (a partially-stratified flow, low meanvelocity of the mixture) high density waves tend to beamplified. This process is associated with the hydro-dynamic interaction between the granular bed at thebottom of a pipeline and the suspension stream abovethe bed. The strongest amplification of high densitywaves occurs at mixture velocities around or below thedeposition limit value. The development of densitywaves and the mechanisms leading to the deformationof density waves were discussed recently (Matousek,2001).

A numerical model that uses a simplified description ofmechanisms governing the unsteady flow of partiallystratified slurry in order to simulate a development of adensity wave along a long horizontal pipeline is presented.The model is two-dimensional; it handles the 2-D massexchange within slurry flow. The vertical exchange ofmass between the bed and the suspension layer above the bed is quantified using applied equations forthe settling rate and the erosion rate. The adoptederosion-rate equation is preliminary and requires furtherinvestigation.

As a result of density fluctuations, the pump dischargepressure and vacuum will change with respect to time

Numerical Simulation of the Development of Density Waves in a Long Pipeline and the Dynamic System Behaviour

S.A. Miedema, Z. Lu and V. Matousek

Numerical Simulation ofthe Development ofDensity Waves in a LongPipeline and the DynamicSystem Behaviour

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Dr. S.A. Miedema holds an MSc degreein Mechanical Engineering (DelftUniversity of Technology, The Nether-lands, 1983, with honors) and a PhDdegree (Delft University, 1987). Since1987 he has been Associate Professor atthe Dredging Engineering Chair andEducational Director (1996-2000).Currently he is involved in researchand education at Delft University,especially with international coopera-tion in Europe, China and Vietnam.

Sape A. Miedema

Lu Zhihua holds an MSc degree inMechanical Engineering (DelftUniversity of Technology, 2002). Since 2002 he has been lecturing andconducting research at the Chair of Dredging Technology, Hohai University, Changzhou, P.R. China.

Lu Zhihua

Dr. Vaclav Matousek holds a Mastersin Civil Engineering (Czech TechnicalUniversity, 1986) and a PhD degree inmechanical engineering (Delft Univer-sity of Technology, 1997). Since 1996he has been employed by the DelftUniversity of Technology, SectionDredging Engineering. His conductsresearch on dredging processes, in particular on hydraulic transport.

Vaclav Matousek

and the pipeline resistance will change with respect totime and place. A change of the discharge pressure willresult in a change of the torque on the axis of the pumpdrive on one hand and in a change of the flow velocityon the other hand. The mixture in the pipeline has toaccelerate or decelerate. Since centrifugal pumpsrespond to a change in density and solids properties atthe moment the mixture passes the pump, while thepipeline resistance is determined by the contents ofthe pipeline as a whole, this forms a complex dynamicsystem. The inertial pressure of the mixture has to beadded to the resistance of the mixture. In fact, theinertial pressure is always equal to the differencebetween the total pressure generated by the pumpsand the total resistance of the mixture in the pipelinesystem. If this difference is positive (the pump pressurehas increased as a result of an increase of the mixturedensity), the mixture will accelerate. If negative, themixture will decelerate (Miedema, 1996).

As a result of the acceleration and deceleration, the mixture velocity (line velocity) will vary as a functionof time. To realise a stable dredging process, it isnecessary to have a line velocity that will not vary toomuch. The line velocity can be controlled by varying therevolutions of one of the dredge pumps, where the lastpump is preferred.

Of course the result of flow control depends on thepump/pipeline layout. If this layout has not beendesigned properly flow control cannot correct a baddesign. If this layout however has been well designed,flow control can control the line speed and can preventthe occurrence of cavitation.

Introduction

During dredging operations the density of mixturetransported along the pipeline of a conveying systemvaries in time and space. The density waves generatedat the inlet of the system tend to transform their shape while moving along the pipeline. This process isassociated with the hydrodynamic interaction betweenthe granular bed at the bottom of a pipeline and thesuspension stream above the bed. The strongestamplification of high density waves occurs at mixturevelocities around or below the deposition limit value.

The development of density waves and themechanisms leading to the deformation of densitywaves were discussed recently (Matousek, 1997,2001; Talmon, 1999).

Previously, the stratified flow in the long pipeline wasanalysed by using the principles of a two-layer modelwith a fixed position of the interface between the layers.A two-layer model is a one-dimensional model thatsimplifies the internal structure of a settling-mixture flowinto a flow pattern composed of a particle-rich lowerlayer and a particle-lean upper layer. The analysis of thewave-amplification process in a long pipeline requiresfurther refinement to implement the effects of themass exchange caused by the settling flux and theerosion flux through the interface between the layers.

The modelling of the density-wave deformationrequires that a one-dimensional two-layer model(longitudinal solids transport only) is replaced by a two-dimensional layered model that takes into account thevertical exchange of solids between the contact bedand the flow of suspension above the bed.

A model predicting the amplification of a density waveas a result of the exchange of solids mass in the direction perpendicular to the flow direction requiressuccessful formula for both the settling flux and theerosion flux through the (virtual) interface betweenlayers. The fluxes seem to be very sensitive to solidsconcentration at the interface, as must also be theformula determining the fluxes. As yet, the pick-upfunctions available for the prediction of the erosion fluxare not reliable in the high concentrated flows typicalfor slurry pipelines.


Element: 1 i-1 i+1 i+1 ni

12

Figure 1. Elements of a pipeline filled with unsteady solids flow.

Figure 2. The transport phenomena simulated by the 2-D

model.

diffusion

flow-in

setting erosion

diffusion

flow-out

Element: i-1

Bed layer

Suspended load

i i +1

to the pipe diameter, particle size, slurry velocity andconcentration. At this stage of investigation, the effectof turbulent diffusion is not taken into account in the 2-D model.

SettlingThe dis-equilibrium between the solids settling rate andthe erosion rate leads to the solids transport in thevertical direction (perpendicular to the main flow direc-tion). This causes changes in the thickness of the bedand in the volumetric concentration of solid particles inthe upper layer.

DESCRIPTION OF THE 2-D MODEL FOR

UNSTEADY FLOW OF SOLIDS IN A PIPELINE

Model structureIf the flow of solids is unsteady the flow structure (the velocity and concentration profiles) varies not onlyin time but also in space, i.e. along a pipeline length. To be able to simulate the unsteady flow on basis of itsinternal structure, important parameters in both timedomain and space domain must be identified. To han-dle the simulation in space domain properly, a pipelinemust be divided into a number of elements. The flow ineach element is split into two layers: the lower layerrepresents a granular bed (either stationary or sliding)and the upper layer represents the suspension flow.Since the solids flow is unsteady (the density of slurryvaries along the pipelines and thus is different indifferent elements), the bed thickness is considered tobe different in different elements. Figure 1 shows aslurry pipeline divided into elements for the modelpurposes.

Modeled transport phenomenaThe conservation of mass must be satisfied in themodel. The mass exchange takes place in two direc-tions: horizontal and vertical. The horizontal transport ofsolids (the transport due to the pressure gradient in apipeline) is given by the following equation

dm = Q . t . Cv,up �s [1]

in which dm is mass differential in an element; Q is the flow rate of slurry; t is the time step; Cv,up is thevolumetric concentration of solids in the upper layerand �s is the density of the solid. During the simulation,at each moment given by t, the Cv,up is the only variablein different elements along the pipeline, the flow rate ofslurry is considered constant.

The horizontal transport of solid particles is influencedby horizontal turbulent diffusion, other possible effectsas those of interparticle collisions are neglected. In thevertical direction, the mass exchange can be definedinto two processes: settling and erosion. The Figure 2summarises the transport phenomena implemented inthe 2-D model of unsteady flow of solids in a slurrypipeline.

DiffusionThe turbulent-diffusion process is quite complex. In thesimplified way, it can be modelled as similar to themolecular diffusion using

fdif,x = –kx . �c�x [2]

in which fdif,x is the diffusion flux owing to turbulence in the x-direction and kx is the factor of longitudinaldispersion. A suitable value for the factor kx is subject tofurther investigation. The factor seems to be sensitive


13

Ero

sio

n f

lux

[kg

/m s

]

Cvd [-]

Volume concentration [-]

218

16

14

2

0

8

6

4

2

00.1 0.2 0.3 0.4 0.5 0.6

Erosion flux for Vm=3.15m/sErosion flux for Vm=3.5m/sErosion flux for Vm=3.8m/s

Figure 3. The erosion flux using the classical formula (Eqs. 4)

for different solids concentrations and mean velocities of

slurry in a pipeline.

Ero

sio

n f

lux

[kg

/m s

]

Cvd


2

16

14

4

2

00.1 0.2 0.3 0.4 0.5 0.6

Erosion flux for Vm=3.15m/sErosion flux for Vm=3.5m/sErosion flux for Vm=3.8m/s

Figure 4. The erosion flux using the adapted formula (Eq. 7) for

different solids concentrations and mean velocities of slurry in

a pipeline.

Settling process presents the ability of the particles tosettle from upper layer to the bed layer. Normallyhindered settling velocity is applied to determine thesettling process. It is derived as

vth = vt. (1 – Cv,up )

m [3]

in which vth is the hindered settling velocity of solidparticles; vt is the terminal settling velocity of a solidparticle and m is the empirical Richardson-Zakicoefficient.

ErosionThe velocity of the suspension flow above the bed ishigher than the bed velocity. If the velocity differential ishigh enough, the top of the bed is eroded. During theerosion process the particles from the top of the bedcan be picked up by the suspension flow. The parametercalled the erosion velocity evaluates the capability ofthe suspension flow to pick up particles from thegranular bed. The erosion velocity has an oppositedirection to the settling velocity. The equation for theerosion velocity is called the pick-up function.

Basically, the erosion velocity (the erosion rate) isdependent on the Shields number. The Shields numberincreases with the increasing relative velocity of theflow above the bed. The literature proposes a numberof erosion-rate models. Unfortunately, the models areconstructed for conditions rather different from those inslurry pipelines, i.e. namely for flow of water or verylow-concentrated mixture above a stationary bed (seee.g. Van Rijn 1984, Cao 1997, Fernandez-Luque 1974).The equation for the erosion velocity

ve = 1.1 . ( � – �cr ) [4]

is used to plot the erosion flux in Figure 3. In Equation 4,� is the Shields number and �cr is the critical Shieldsnumber (the threshold value for the initial erosion).

The erosion flux is calculated as

E = �s. ve

. Cvd [5]

Observations in a slurry pipeline indicate that the shearstress at the top of the bed and so the Shields numbermay vary significantly with the concentration of solidsabove the bed (e.g. Matousek, 1997). The classicalerosion-velocity formulae do not include the effect ofthe solids concentration directly. For the purposes ofslurry pipelines this parameter should be implementedto the erosion-velocity equation. Furthermore, in theclassical erosion-velocity formulae the exponent ofShields number is usually considered higher than 1.

This means that the erosion flux simply keeps increasingwith the increasing Shields number and so with theincreasing solids concentration Cvd . This providesunrealistically high values of erosion flux in highlyconcentrated flows as shown on Figure 3.However, it can be expected that at extremely highconcentrations of solids the hindering effects reducethe erosion process (Talmon 1999, Van Rhee andTalmon, 2000) so that the erosion rate diminishes.

There are research results available on the effect ofsolids concentration on the erosion rate in a slurrypipeline. Therefore, as an initial approach, the hinderingeffect was considered here as similar to that for thesolids settling so that the hindering effect can berepresented in the erosion-rate formula by the term(0.55 – Cv)

�. The erosion velocity is then determinedusing the following equation

ve = � . ( � – �cr ) � ( 0.55 – Cv,up )

� [6]

in which �,� are the empirical coefficients. The con-stant 0.55 represents the concentration of solids in aloose-packed bed. The calibration of this simplifiedequation using a limited number of data (see below) led


14

Hindered settling process (V )

sedimentation velocity

Area of the top of the bed

Hindered settling process (V )

( )

Vertical velocity of the to of the

bed (V )V =0bed

th

th esed bede

bed

V

M

V V

fn v v v

V

bed

sed bedth e

V

=

=

- -

, ,

Figure 5. Computation of vertical mass exchange in the 2-D model.

lower than approx. 1250 kg/m3 the settling flux isbigger than the erosion flux, thus a portion of solidparticles is transferred from the suspension to the bed,the thickness of the bed increases. In denser suspen-sion (approx. denser than 1400 kg/m3) the erosion fluxfrom the top of the bed predominates and the particlesare picked up from the bed, the density of suspensionincreases and the bed thickness decreases.

The adapted erosion-flux formula (Eq. 4) can be calibrat-ed using the experimental data so that the calculateddisequilibrium (see Figure 6) for the velocity near thedeposition-limit value (3.15 m/s) shows the sametrends as the measurements. The plot shows that forthe above chosen conditions the model predicts theequilibrium between the settling flux and the erosionflux in slurry of the volumetric concentration of about0.25 (slurry density of about 1415 kg/m3). In the parts ofthe pipeline that are occupied by the slurry of densitylower than this value the model predicts the predomi-nation of the settling flux and thus gradual decrease ofsolids concentration in the suspension flow. In theparts occupied by the slurry of density higher than 1415 kg/m3 (and lower than approximately 1930 kg/m3)the model predicts the dominant effect of the erosionand thus a gradual increase of solids concentration inthe suspension flow. The amplification of the high-density peaks does not occur at velocities significantlyhigher than the deposition-limit velocity. This isbecause the majority of particles are supported byturbulence (travels within suspension flow) and the bedis very thin. Under this condition the interaction ismissing between two layers that is necessary for thedevelopment of the density waves.

to the following preliminary form of the erosion-velocityequation

ve = 1.1 . ( � – �cr )1.9 . ( 0.55 – Cvd )

0.9 [7]

This adapted erosion-rate equation provides a ratherdifferent shape of the curve than the classical model(compare Figures 3 and 4). The adapted model seemsto provide more realistic trends, but it must be stressedthat the form of the model and the values of the coefficients have not been verified by experiments. A final form of the erosion-rate equation for slurrypipelines is a subject for further investigation.

Mass exchange between bed and suspension flowIf there is dis-equilibrium between the settling flux and the erosion flux, the mass exchange takes placebetween the granular bed and the suspension flow andthe thickness of the bed varies. The relative velocitythat represents the mass exchange is called thesedimentation velocity, vsed, and can be defined as

vsed = vth – ve – vbed [8]

In Eq. 8, vbed is the velocity of the top of the bed, i.e.the vertical velocity with which the top of the bedchanges its position.

The sedimentation velocity represents the massexchange between the contact bed and the suspen-sion flow properly for channels in which the areathrough which the mass fluxes release does notchange with the vertical position of the top of the bed,i.e. for rectangular channels. In circular pipelines, however, the area of the top of the bed variessignificantly the vertical position of the top of the bed(with the bed thickness), and then an iteration isrequired to determine the sedimentation-velocity value.The iteration process is described in Figure 5.

SIMULATIONS

The 2-D model is calibrated and tested using the dataobtained from the measurements in a long 650-mmpipeline transporting the medium sand of d50 = 250microns (for details over the measurements and datasee Matousek 1997 and Matousek 2001).

Relation between settling and erosion fluxesThe measurements have shown that in flow near thedeposition-limit velocity density peaks smaller thanapproximately 1250 kg/m3 tended to flatten along thelong horizontal pipeline while peaks larger than approxi-mately 1400 kg/m3 tended to amplify. Considering thevertical exchange of solids between the bed and thesuspension as the mechanism responsible for thedensity-wave transformation, the observed phenomenacan be interpreted as follows. In suspensions of density


15

Ero

sio

n a

nd

Set

tlin

g F

lux

[kg

/m s

]C

2

0

1

2

3

4

5

6

7

8

0.1 0.2 0.3 0.4 0.5 0.6

Erosion flux for Vm=3.15m/sSettling flux for Vm=3.15m/s

vd


Figure 6. Comparison of settling and erosion fluxes according

to the 2-D model in a 650-mm pipeline occupied by slurry of

medium sand (d50=0.25 mm) (Vm=3.15 m/s).

The model with the implemented flux equations forvertical mass exchange can simulate a deformation ofthe density waves along a long horizontal pipeline. The plots in Figures 7 and 8 show the simulationresults for the conditions described above (a pipeline of the diameter 650 mm and sand 250 microns). The pipeline is 1200 m long and the simulated timeperiod is 360 seconds. One time step in the simulationrepresents 0.3 second, i.e. 1200 steps are made during the entire simulation. The plots in the Figures 7and 8 indicate the volumetric concentration of solids in the suspension flow simulated in the element 1 (the position at the inlet to the pipeline), element 500

(the position 500 metres behind the inlet) and theelement 800 (800 metres behind the inlet). The figuresshow how the set of density waves changes its shapewhile passing through the pipeline.In Figure 7, the slurry pipeline operates at the meanslurry velocity round the deposition-limit velocity (3.15 m/s). There is a granular bed of a considerablethickness at the bottom of the pipeline. The simulationindicates that owing to the vertical exchange of massbetween the bed and the suspension flow above thebed two large density peaks gradually increase andthree small peaks gradually decrease while passingthrough the long pipeline from element No.1 to No. 800.These trends are in accordance with those observed inthe field pipeline during the tests (Matousek 2001).

In Figure 8, the slurry pipeline operates at the meanslurry velocity far above the deposition-limit velocity(3.8 m/s). At this velocity the sliding bed at the bottomof the pipeline is very thin and tends to dissolve. This isprimarily owing to higher ability of carrier turbulence tokeep particles suspended and also owing to highererosion than at velocity 3.15 m/s. Under these condi-tions the deformation of the density waves is differentfrom that in the pipelines occupied by a thick bed.

The waves change their shape much less than in thelayered flow as can be seen in Figure 8. The frontpeaks of the set of the peaks tend to increase afterentering the pipeline but their increase stops when thebed disappears in the pipeline and there is no materialto feed the peaks. The rest of the peaks do not growfor the same reason. The increase of concentration ofsolids to the limit value 0.20 in the suspension flow infront of the set of the peaks in elements No. 500 andNo. 800 indicates that the bed dissolved there alreadybefore the set of the peaks arrived. The concentrationvalue 0.20 was reached when all particles traveled insuspension, thus there was no bed.

THE PUMP / PIPELINE SYSTEM DESCRIPTION

In a steady state situation, the revolutions of the pumpsare fixed, the line speed is constant and the solidsproperties and concentration are constant in thepipeline. The working point of the system is the inter-section point of the pump head curve and the pipelineresistance curve. The pump curve is a summation ofthe head curves of all pumps. The resistance curve is asummation of the resistances of the pipe segmentsand the geodetic head. Figure 9B shows this steadystate situation for the system used in the case study(Figure 9A) at 6 densities ranging from clear water up toa density of 1.6 ton/m3. In reality, the solids propertiesand concentration are not constant in time at thesuction mouth. As a result of this, the solids propertiesand concentration are not constant as a function of theposition in the pipeline.


16

0.5

0.4

0.3

0.2

0.1

200 400 600 800 1000 1200

Cv,u

p 1

0.5

0.4

0.3

0.2

0.1

200 400 600 800 1000 1200

Cv,u

p 2

0.50.4

0.30.20.1

200 400 600Time step (0.3s per step)

800 1000 1200

Cv,u

p 3

Figure 7. Deformation of density waves along the long pipeline

(slurry velocity round the deposition limit velocity) observed

at the inlet to the pipeline, 500 metres behind the inlet and

800 metres behind the inlet.

0.4

0.3

0.2

0.1

2000

0

0

400 600 800 1000 1200

Cv,u

p 1

0.4

0.3

0.2

0.1

200 400 600 800 1000 1200

Cv,u

p 2

0.4

0.3

0.2

0.1

200 400 600Time step (0.3s per step)

800 1000 1200

Cv,u

p 3

Figure 8. Deformation of density waves along the long pipeline

(slurry velocity far above the deposition limit velocity) observed

at the inlet to the pipeline, 500 metres behind the inlet and

800 metres behind the inlet.

leaves the pipeline. Because the line speed is notconstant, the length of the segment added is notconstant, but equals the line speed times the timestep. For each segment the resistance is determined,so the resistance as a function of the position in the pipeline is known. This way also the vacuum and

To be able to know these properties as a function of theposition in the pipeline, the pipeline must be divided intosmall segments according to the above discussions.These segments move through the pipeline with theline speed. Each time step a new segment is added atthe suction mouth, while part of the last segment


17

Figure 9A. The pump/pipeline system used.

0.00 0.40 0.80 1.20 1.60 2.00 2.40 2.80 3.20 3.60 4.000

470

940

1410

1880

2350

2820

3290

3760

4230

4700

Flow in m^3/sec

To

tal

Hea

din

kPa

1.0 1.2 1.4 1.6 1.8 2.00

2400

4800

7200

9600

12000

Density in ton/m^3

To

tal

Po

wer

inkW

0 410 820 1230 1640 2050 2460 2870 3280 3690 4100-100

300

700

1100

1500

1900

Distance from suction mouth in m

Pre

ssu

rein

kPa

1.0 1.2 1.4 1.6 1.8 2.00

1200

2400

3600

4800

6000

Density in ton/m^3

Pro

d.i

nm

^3/

ho

ur

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 100000

12002400360048006000

Length of discharge line in m

Pro

d.i

nm

^3/

ho

ur

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 100000.000.801.602.403.204.00

Length of discharge line in m

Flo

win

m^

3/se

c

Vcrit Water Rho: 1.144 Rho: 1.258 Rho: 1.372 Rho: 1.486 Rho: 1.600

Stationary Pump Behaviour Windows V4.01 - Torque Limited:12-29-2000 - 04:35:28

C:\PROGRA~1\CSDPRO~1\PIPELINE\PIPELI~1.DAT in Default

Figure 9B. Characteristics of the pump/pipeline system.


18

0 101 202 303 404 505 606 707 808 909 10101.0

1.2

1.4

1.6

1.8

2.0

1010 1111 1212 1313 1414 1515 1616 1717 1818 1919 20201.0

1.2

1.4

1.6

1.8

2.0

2020 2121 2222 2323 2424 2525 2626 2727 2828 2929 30301.0

1.2

1.4

1.6

1.8

2.0

3030 3131 3232 3333 3434 3535 3636 3737 3838 3939 40401.0

1.2

1.4

1.6

1.8

2.0

Pipeline section 1

mto

n/c

u.m

Pipeline section 2

m

m/s

ec

Pipeline section 3

m

m/s

ec

Pipeline section 4

m

cu.m

/sec

Pro

gram

Date

Tim

eE

lapse

d

:D

ynam

icP

um

pB

ehavio

ur

Win

do

ws

V:

Decem

ber

29,2000

:06:59:28

:00:12:39

Figure 10. The density distribution in the pipeline after 12 minutes.

0 101 202 303 404 505 606 707 808 909 10101.0

1.2

1.4

1.6

1.8

2.0

1010 1111 1212 1313 1414 1515 1616 1717 1818 1919 20201.0

1.2

1.4

1.6

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2.0

2020 2121 2222 2323 2424 2525 2626 2727 2828 2929 30301.0

1.2

1.4

1.6

1.8

2.0

3030 3131 3232 3333 3434 3535 3636 3737 3838 3939 40401.0

1.2

1.4

1.6

1.8

2.0

Pipeline section 1

m

ton

/cu

.m

Pipeline section 2

m

m/s

ec

Pipeline section 3

m

m/s

ec

Pipeline section 4

m

cu.m

/sec

Pro

gram

Date

Tim

eE

lapsed

:D

ynam

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29,2000:

07:03:49:

00:17:01


5 m below water level. The main pump and the boosterpump are placed 10 m above water level. The pipelinelength between ladder and main pump is 30 m,between main pump and booster pump 2000 m, as isthe length of the discharge line. The pipe diametersafter the ladder pump are 0.61 m. The total simulationlasts about 30 minutes and starts with the pipelinefilled with water.

After the pumps are activated, the mixture density atthe suction mouth increases to a density of 1.6 ton/m3,stays at that value for a period of 2 minutes and thendecreases back to the water density.

Sand is used with a d15 of 0.25 mm, a d50 of 0.50 mmand a d85 of 0.75 mm. The density block wave movesthrough the system, subsequently passing the threepumps.

For the simulation the following scenario is used:00 minutes start of simulation, the timer is started and

all parameters will be recorded01 minutes start of ladder pump, the ladder pump drive

behaves according to a first order system04 minutes start of main pump, the main pump drive

behaves according to a first order system07 minutes start of booster pump, the booster pump

drive behaves according to a first ordersystem

08 minutes start of the flow control system (optional)

the discharge pressure can be determined for eachpump. If vacuum results in cavitation of one of thepumps, the pump head is decreased by decreasing thepump density, depending on the time the pump iscavitating.

CASE STUDY

The aim of this case study is twofold; first it showsevents caused by the dynamic behaviour of the systemthat cannot be predicted by steady state calculations;second it shows the application of the above theory ofdensity waves. A problem in defining a system and ascenario for the simulation is, that the system canconsist of an infinite number of pump/pipeline combina-tions, while there also exists an infinite number ofsolids property/concentration distributions as a functionof time. For this case study, a system is definedconsisting of a suction line followed by three pump/pipeline units (see Figure 9A). The first pump is a ladderpump, with a speed of 200 rpm, an impeller diameterof 1.5 m and 1050 kW on the axis (see Figure 9A). The second and the third pump run also at a speed of 200 rpm, have an impeller diameter of 2.4 m and3250 kW on the axis. The time constants of all threepumps are set to 4 seconds. The time constant of thedensity meter is set to 10 seconds. The suction linestarts at 10 m below water level, has a length of 12 mand a diameter of 0.69 m. The ladder pump is placed


19

0 101 202 303 404 505 606 707 808 909 10101.0

1.2

1.4

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1010 1111 1212 1313 1414 1515 1616 1717 1818 1919 20201.0

1.2

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2020 2121 2222 2323 2424 2525 2626 2727 2828 2929 30301.0

1.2

1.4

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3030 3131 3232 3333 3434 3535 3636 3737 3838 3939 40401.0

1.2

1.4

1.6

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2.0

Pipeline section 1

m

ton

/cu

.m

Pipeline section 2

m

m/s

ec

Pipeline section 3

m

m/s

ec

Pipeline section 4

m

cu.m

/sec

Pro

gram

Date

Tim

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20

00:00 00:03 00:06 00:09 00:12 00:15 00:18 00:21 00:24 00:27 00:300.0

2.0

4.0

6.0

8.0

10.0Line speed vs time

Timem

/sec

00:00 00:03 00:06 00:09 00:12 00:15 00:18 00:21 00:24 00:27 00:301.00

1.20

1.40

1.60

1.80

2.00Density vs time

Time

ton

/m^3

00:00 00:03 00:06 00:09 00:12 00:15 00:18 00:21 00:24 00:27 00:300

800

1600

2400

3200

4000Total power vs time

Time

kW

00:00 00:03 00:06 00:09 00:12 00:15 00:18 00:21 00:24 00:27 00:300

800

1600

2400

3200

4000Production vs time

Time

m^

3/h

ou

r

Dyn

amic

Pu

mp

Beh

aviou

rW

ind

ow

sV

4.01D

ecemb

er29,2000,07:16:30

AM

Flo

wTim

eS

eries

Figure 13. Line speed, density, total power and situ production as a function of time.

00:00 00:03 00:06 00:09 00:12 00:15 00:18 00:21 00:24 00:27 00:300

80

160

240

320

400Pump speed vs time

Time

rpm

00:00 00:03 00:06 00:09 00:12 00:15 00:18 00:21 00:24 00:27 00:300

400

800

1200

1600

2000Pump power vs time

Time

kW

00:00 00:03 00:06 00:09 00:12 00:15 00:18 00:21 00:24 00:27 00:30-100.0

-60.0

-20.0

20.0

60.0

100.0Pump vacuum vs time (-=vacuum, +=pressure)

Time

kPa

00:00 00:03 00:06 00:09 00:12 00:15 00:18 00:21 00:24 00:27 00:300

80

160

240

320

400Pump discharge pressure vs time

Time

kPa

Dyn

amic

Pu

mp

Beh

aviou

rW

ind

ow

sV

4.01D

ecemb

er29,2000,07:14:53

AM

Pu

mp

1Tim

eS

eries

Figure 14. Speed, power, vacuum and discharge pressure of the ladder pump vs. time.

speed, power, vacuum and discharge pressure of thethree pumps as a function of time.

As can be seen in Figure 13, the line speed increasesslower then the pump speed, owing to the inertialeffect. When the density wave passes the ladder andmain pump (from 10 to 13 minutes), the dischargepressure of these pumps increases, resulting in ahigher line speed. When the density wave passes thebooster pump (from 16 to 19 minutes) the sameoccurs for the booster pump. After about 10 minutes of simulation time, all three pumps are activated and asteady state situation occurs in the system.Then the mixture density at the suction mouth increasesfrom water density to about 1.6 ton/m3. First theresistance in the suction line increases, resulting in asudden decrease of the ladder pump vacuum anddischarge pressure. When the density wave reachesthe ladder pump, the discharge pressure increases,owing to the higher density. When after 2 minutes, the density decreases to the water density, first theresistance in the suction line decreases, resulting in anincrease of the ladder pump vacuum and dischargepressure, followed by a decrease of the dischargepressure when the clear water reaches the ladderpump (see Figure 13). The distance between the ladderpump and the main pump is 30 m. With an average linespeed of 5 m/s, the density wave passes the mainpump 6 seconds after passing the ladder pump.

10 minutes increase mixture density to about 1.6 ton/m3

12 minutes decrease mixture density to water density12 minutes take sample of density distribution in

pipeline17 minutes take sample of density distribution in

pipeline22 minutes take sample of density distribution in

pipeline28 minutes stop simulation and create graphs

Figures 10, 11 and 12 show the density wave at 12, 17 and 22 minutes of simulation time. At 12 minutesthe density wave occupies the suction line, the ladderpump and the main pump and part of the pipelinebehind the main pump. At 17 minutes the densitywave occupies the last part of the pipeline before thebooster pump, the booster pump and the first part of the discharge line after the booster pump. At 22 minutes the density wave occupies the middlepart of the discharge line.

Figure 13 shows the line speed, the density, the totalpower consumed and the production as a function oftime. The line speed, the density and the productionare determined at the inlet of the ladder pump.

The density is determined using the mathematicalbehaviour of a density transducer with a time constantof 10 seconds. Figures 14, 15 and 16 show the pump


21

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Figure 15. Speed, power, vacuum and discharge pressure of the main pump vs. time.

The same phenomena as described for the ladderpump, occur 6 seconds later for the main pump (see Figure 15). As a result of the increased dischargepressure of ladder and main pump during the densitywave, the line speed will also increase (see Figure 13),but because of the inertial effects, this increase and 2 minutes later decrease is not as steep. One could saythat there is a time delay between the immediateresponse of the discharge pressure of the pumps onchanges in the density in the pumps and the responseof the line speed on changes in the discharge pressure.

At 12 minutes and about 45 seconds, the density wavehas left the main pump, but has not yet reached thebooster pump. The head of each pump is determinedby the density of water, but the line speed is stilldetermined by the head resulting from the mixture andthus to high. The resistance in the pipe between mainand booster pump is high because of the mixture,resulting in a decrease of the booster pump vacuumand discharge pressure. As the line speed decreases,the booster pump vacuum and discharge pressure willstay in a semi-steady state situation. When the densitywave reaches the booster pump, the total head of thebooster pump increases, resulting in an increase of theline speed. This occurs after about 16.5 minutes ofsimulation time. Since the total head of ladder and mainpump does not change, the booster pump vacuum willhave to decrease to pull harder on the mixture in the

pipeline before the booster pump. This results in theoccurrence of cavitation of the booster pump, limitingthe total head of the booster pump and thus the linespeed. The cavitation causes a very instable behaviourof the booster pump as is shown in Figure 16.

Since the density wave moves from the suction line tothe discharge line, the booster pump vacuum and dis-charge pressure both increase when the density wavemoves through the booster pump. After 18.5 minutesthe density wave leaves the booster pump. The totalhead of the booster pump decreases sharply, while theline speed decreases slowly.

The fluid in the pipeline before the booster pump pushesand the fluid after the booster pump pulls, resulting in a quick increase of the booster pump vacuum and adecrease in the booster pump discharge pressure.

As the line speed decreases, the discharge pressure willincrease again. After 23 minutes of simulation time, thedensity wave starts leaving the pipeline. Two minuteslater the density wave has completely left the system.Because of the decreasing resistance during this time-span, the line speed will increase slightly, resulting in asmall decrease of the vacuum and discharge pressure ofeach pump, while the total head remains constant.

The total power will also increase slightly because of this.


22

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Figure 16. Speed, power, vacuum and discharge pressure of the booster pump vs. time.


23

Conclusions

The simplified two-dimensional model has beenproposed for simulation of dynamic effects of unsteadysolids flow in a horizontal slurry pipeline. This model is a first attempt to simulate the deformation of densitywaves observed in long pipelines connected with adredger.

The results of the model simulation show the sametrends in the development of the density waves asthose observed in practice. Both the physical processof the unsteady solids flow and its simulation requirefurther investigation. Special attention must be focusedto erosion in high concentrated slurries and effect ofturbulent diffusion on the solids distribution in suspen-sion flow.

The behaviour of a multi pump/pipeline system isdifficult to understand. As mentioned before, an infinitenumber of system configurations and soil conditionsexist. Systems are usually configured, based on steadystate calculations, while the dynamic behaviour isignored. Combining the steady state approach forpipeline resistance with the dynamic behaviour ofpumps, pump drives and the second law of Newton,the dynamic behaviour can be simulated.

However, a number of assumptions had to be made.These assumptions are:– there is no longitudinal diffusion in the pipeline, – the pump drive behaves like a constant torque

system,– the pipeline resistance is determined using the

Durand theory, – the centrifugal pump obeys the affinity laws.

The simulations however show the occurrence ofphenomena that are known in practice. The use of automation/flow control works well for the caseconsidered, but many cases have to be considered tobe sure the flow control is stable. In the case considered,the density measured has not been used for the flowcontrol to surpress cavitation. Since the hydraulictransportation process is governed by differentparameters, it is impossible to fully control the processby measuring just 1 parameter and controlling just 1 parameter. Whether these assumptions are valid willbe subject of further research.

One should consider that mathematical modelling is an attempt to describe reality without having any presumption of being reality.

References

Bree, S.E.M. de (1977).“Centrifugal Dredgepumps“. IHC Holland 1977.

Cao, Z (1997).“Turbulent Bursting-Based Sediment Entrainment Function.“

Journal of Hydr. Eng, Vol 123, No.3, March 1997.

Fernandez-Luque (1974). Erosion and Transport of Bed-Load Sediment. Dissertation,

Krips Repro BV, Meppel, The Netherlands.

Gibert, R.,“Transport Hydraulique et Refoulement des Mixtures en

Conduites“.

Matousek,V. (1997).Flow Mechanism of Sand-Water Mixtures in Pipelines. Ph.D.

Thesis, DUT Press, Delft, The Netherlands.

Matousek, V. (2001).“On the Amplification of Density Waves in Long Pipelines

Connected with a Dredge.“ Proceedings 16th World Dredging

Congress, Kuala Lumpur, Malaysia.

Miedema, S.A. (1996).“Modeling and Simulation of the Dynamic Behavior of a

Pump/Pipeline System“. 17th Annual Meeting & Technical

Conference of the Western Dredging Association. New Orleans,

June 1996.

Miedema, S.A. (2000).“Dynamic Pump Behaviour Windows V4.01“. Software, Delft

2000.

Rijn, L.C, van (1984). “Sediment Pick up Function.“ Journal of Hydr Eng. Vol. 110,

No, 10, Oct 1984

Talmon, A.M. (1999). “Mathematical Analysis of the Amplification of Desity

Variations in Long-Distance Sand Transport Pipelines.“

Hydrotransport 14, Maastricht, Netherlands, pp.3-20.

Van Rhee and Talmon (2000). “Entrainment of Sediment (or Reduction of Sedimentation)

at High Concentration.“ 10th International Conference on

Transport and Sedimentation of Solid Particle. Wroclaw, Poland,

September 2000, pp. 251-262.

Wilson, K.C., Addie, G.R. and Clift, R. (1992). “Slurry Transport Using Centrifugal Pumps“. Elsevier Science

Publishers Ltd. 1992.

The museum has spent a great deal of attention to thecreation of the canal and the celebration of its openingin 1869. The centerpiece of the exhibition is a model ofthe Suez Canal surroundings 15 metres long, built bythe museum, located in a separate tent in which theclimate and atmosphere of the real canal is replicated(see photo).

The exhibition will be on display through January 3 2004.The Museum can be found at Molendijk 204,Sliedrecht, The Netherlands and is opened Tuesdaythrough Saturday from 14.00 to 17.00. For furtherinformaiton contact [email protected].

The History of the SuezThe desire to link the Mediterranean Sea with a water-way to the Red Sea is very old indeed. Already fortycenturies ago, the Egyptian Pharaohs tried to createsmall canals from a branch of the Nile through themultiple northern lakes to the Gulf of Suez. The canalssilted up quickly and disappeared, but the idea of apermanent connection did not. After the conquest ofEgypt by the French in 1799, Napoleon ordered aserious examination of the possibilities of building acanal through the Isthmus of Suez. The resultsindicated a difference in depth of some 10 metresbetween the two seas. To build the necessary locks inorder to span this difference was beyond the reach ofthe technology of the times.

Around 1830 the British discovered that this differencein depth was only a few centimetres that could easilybe accommodated. But a concession to begin diggingwas denied them. In 1846 the Société des Etudes pourle Canal de Suez was founded and actively began topromote the idea of a connection through the Isthmus.A member of the Society, the Austrian-Italian engineerAlois von Negrelli had developed several plans. Pasha Mohammed Said, a progressive Europhile, who was friendly with the Frenchman Ferdinand deLesseps, attempted to realise the plans. De Lessepswas the consul in Cairo and, through his relationshipwith the French Empress Eugénie, had a great deal ofinfluence on public life in Egypt. Another close friend of

The Suez Canal is the stuff that dreams are made of,and certainly the dreams of engineers and politicians.From Pharoahs to present-day presidents and primeministers, many leaders have imagined transformingcertain bodies of water or pieces of land to fit theirvisions. The Suez was clearly one of these places.Fascinated by the enormity of such undertakings, the National Dredging Museum of The Netherlandsdecided to create an exhibition about the Suez Canal.Sponsored by the International Association of DredgingCompanies, the exhibit was opened on July 25, 2003by Engineer Hussein Abdel Rahman Helmy, memberof the Board and Director of the Dredging Division ofthe Suez Canal Company in Egypt.

“The Suez Canal —Camels, Sand and Water”Exhibition at the National DredgingMuseum, Sliedrecht, The Netherlandsthrough January 3 2004


24

A specially built 15-metre-long scale model of the Suez Canal

and its surroundings forms the centerpiece of the exhibition

“Camels, Sand and Water” at the National Dredging Museum

in Sliedrecht, The Netherlands.

The Suez Canal — Camels, Sand and Water

25

De Lesseps was the Netherlands Ambassador toEgypt, Ruyssenaers who also understood the immenseimportance of a water connection between Port Saidand the Suez and who became an ardent advocate forthe canal.

De Lesseps at last won a concession from PashaMohammed Said to exploit the canal dating for 99years from its opening, in an exchange for 15 percentof the profits. In 1858 he established the CompagnieUniverselle du Canal Maritime de Suez with American,British and French support. The investment capital wasset at 200 million French francs. Only half was finallydeposited by the French, as the Americans and Britishdefaulted. So it was left to Said to rescue De Lessepswith a loan of 60 million francs and on April 25 1859 thefirst spade of earth was dug at what would becomePort Said. The total work activities were planned to takesix years.

In 1863 Said died and his successor was the more-English-oriented Pasha Ismael who wanted the agree-ment adapted to be more favourable to his country.Work was stopped for three years. In 1866 a newcompromise was reached with France’s Napoleon IIIthat did not afterall favour Ismael. The plan consisted ofthree parts: a sweetwater canal, the construction ofPort Said and the digging of the canal itself. Theapproach to the canal as such was to make maximumuse of the existing waters such as the Bitter lakes andthe lakes of Timsah and Manzala. In this way only 64 km of the canal went through sand whilst 96 kmwent through the lakes. The sweetwater canal wasnecessary in order to bring water from the Nile to theIsthmus of Suez. This was a piece of desert totallywithout a drop of water. The canal, 8 m wide and 2.4 mdeep was then used as a means of transporting material.It went from the Nile via Ras-el-Wadi to the lake of Timsahand from there branches to the Suez and Port Said.

In total 60,000 forced labourers worked on the canal inthree shifts with the help of shovels, pick axes andbaskets to carry away the sand. During the three yearpause in the project, technology had made dramaticprogress and the work was resumed with the utilisationof digging machines that were rather primitive at thestart, but gradually during the work grew increasinglybetter. Still in the decade between 1859 and 1869about 20,000 workers lost their lives, succumbing toexhaustion and illnesses such as cholera. In 1869 thecanal was ready, only four years behind schedule andwith a price-tag only two times higher than estimated.

On the 17th of November 1896, the French EmpressEugénie officially opened the canal, which was followedby three days of celebrations. In the first years of itsexistence, some three to five ships moved through thecanal per day. Ten years later that had grown to ten perday and between 1900 and 1920 there were fifteen

ships per day. Often ships were moved in convoysbecause the depth and width of the canal did not allowfor passing room throughout, but only at certain placeswhere laybys were constructed. If the ships did not runaground than it took about 40 hours to sail from theMediterranean through to the Red Sea. The sailing timefrom Western Europe to Asia, depending on thedestination, was shortened by 20 to 40 percent, which meant an enormous savings even taking intoconsideration the costs of tolls.

When the canal opened it was 171 km long, at aminimum 58 m wide and only for 22 m was it at adepth of 6 m. Consequently there was almostimmediately a need to broaden and deepen the canaland in 1875 the work was thus begon which actuallycontinues through today. Partially this is the result ofthe expansion in shipbuilding. In 1967 the minimumwidth was 150 m and depth was 12 m, which madethe canal suitable for ships up to 70,000 ton waterreplacement. Transportation of oil was the mostimportant cargo and three quarters of the total canalincome was related to oil.

During the Second World War the canal was of greatstrategic importance for the Allied Forces and fromthen on its fate was tumultuous. From the late 1940sthrough the 1970s, wars in the Middle East closed thecanal and made its use for the Western world inacces-sible. Nationalised by Egypt in 1956, with ships sunk inits waters and De Lesseps’ statue toppled, the SuezCanal was abandoned and the longer route around theCape of Good Hope was resumed. After several inter-ventions by the United Nations, finally in 1975 the canalwaters were once again cleared and opened to allnations by Egyptian President Sadat. The InternationalCourt at the Hague was recognised as the final arbiterof all disputes.

In 1870 485 ships had passed through the canal, in 195011,750 ships and in 1960 18,750. When the canal wasclosed after the Six Day War with Israel, it took until1980 to reach this level again. Once re-opened, theefforts to improve the canal were re-energised, andtoday ships up to 150,000 ton water replacement cantravel through the canal effortlessly. The canal is now210 m wide and 19.5 m deep. To allow for easier andsafer passing manoevres, a 68-km parallel canal wasbuilt. The pedestal of De Lesseps statue is still there,though his statue itself which had been hidden in 1956,has since disappeared without a trace. In the model of the Suez Canal at the Museum, Ferdinand’s statuehas been purposefully placed where it should be, as away of honouring the dreamer and designer of theSuez Canal.

For further information about the canal and its history,see the review of Zachary Karabell’s new book Partingthe Desert on page 28.

Making Dredgers Aware of the Public andthe Public Aware of Dredging

Lecture 3 Bioassays for Sediments Characterisation— The Spanish Experience

Lecture 4 Specific Guidelines for Assessment ofDredged Material – London Convention1972/1976 Protocol

Lecture 5 Latest Trends on Dredging Equipment Lecture 6 The Costs Structure in the Dredging

Industry Lecture 7 Dredging and Marine Works in Palm

Island Project Lecture 8 Environmental Beaches Recovery by

Using Marine Sand BorrowsLecture 9 Deepening of Guadalquivir River Effects:

Siltation, River Banks Erosion and CoastalProgress

Lecture 10 Re-suspension of Sediment by DredgingProcesses

The final programme event was termed a DebateTable, and consists of brief summaries of the talks ofsix panelists. The theme of the panel was, “DredgingToday, Its Social Impact”. The panelists representeddredging contractors, consultancies, academia, andgovernment. Four of these summaries are containedwithin the proceedings.

The shortcomings of the proceedings are few but bearmention. The absence of what has become the tradi-tional inclusion of key words, which are especiallyimportant in the retrieval of information from papersand proceedings as more of them are included insearchable databases, is noted. The lack of a preface orpurpose of the seminar at the outset of the proceed-ings and a table of contents is also noted. The use ofthe loose-leaf binding has utility in some sense, but onthe other, it makes for a less than ideal way to incorpo-rate the proceedings into a technical library.

The papers are readable, in spite of the apparent trans-lation of a few of the papers into English from another

Proceedings of “Dredging Today,” Second International Seminar on Dredging,Avilés, Spain, June 19 – 20, 2003. Loose-leaf bound, 161 pps, A-4 size.

Autoridad Portuaria de Avilés(Port Authority of Avilés)

These proceedings mark the second internationalseminar on dredging held in Aviles. The seminar wassponsored jointly by three organizations; AsociaciónTecnica de Puertos y Costas, the Spanish Section ofPIANC and the Port Authority of Avilés. The programme summarised in the proceedingsconsists of ten lectures and five opening statementsfor a panel discussion. The lectures embody a diverseset of subjects, ranging from dredging equipment,beneficial use of dredged materials, environmentalissues and case studies. The breadth of theprogramme makes for a very interesting and valuablecompilation of technical papers.

Several of the papers bear special mention. The dis-course on Public Awareness of Dredging was particu-larly interesting, as was the update on the LondonConvention guidelines. The other papers presentedsome excellent data, concepts and conclusions andconstitute a valuable addition to the technical literatureon dredging technology, and does so with someemphasis on the Spanish experience and perspective.This is a sector not often represented in the dredgingconferences or seminars, and for that reason the pro-ceedings present a fine opportunity to add literaturefrom this region. Moreover, the programme had goodinternational representation with lectures from the UK,USA, Netherlands and Dubai.

The diversity of the programme may best be demon-strated by a listing of the lectures, or papers:Lecture 1 Dredging Works at Douros and Leixos

Ports, Practical Cases Throughout the lastDecade

Lecture 2 Public Awareness is a Two Way Street —

Charles W. Hummer, Jr.

Books/PeriodicalsReviewed


26

Books/Periodicals Reviewed

27

language. The illustrations and tables were generallywell presented. The proceedings are well worth thetime and cost to incorporate in the technical libraries ofconsultancies, contractors, academia and governmentalagencies.

Information about the Proceedings are available from:Roberto Vidal MartínDravosa Dredging and Marine ContractorsPlaza de Castilla, 3 21.o-A, 28046 Madrid, SpainEmail: [email protected]

Proceedings, Western Dredging Association, Twenty-third Technical Conference and Thirty-fifth AnnualTexas A&M Dredging Seminar, June 10-13, 2003,Chicago, Illinois, USACenter for Dredging Studies, Ocean Engineering Program,Civil Engineering Department, Texas A&M University,College Station, Texas (CDS Report No. 376)Softcover. 363 pp. illustrated.

Edited by Dr. Robert E. Randall

The Western Dredging Association (WEDA) and TexasA&M University continue their long collaboration inconducting dredging conferences. Texas A&M Univer-sity, Center for Dredging Studies, is the only universitylevel technical curriculum dedicated exclusively todredging technology. For many years, the proceedingsemanating from their collaborative conferences havebeen a major source of worthwhile technical papers ondredging related activities. A measure of the internationalreputation of the annual event is the participation ofinternational experts in both the Texas A&M DredgingSeminar as well as the WEDA Technical Conference.

The papers are edited by Robert E. Randall, Ph.D., P.E.,Professor of Ocean and Civil Engineering, Director for Dredging, Center for Dredging Studies, OceanEngineering Program, Civil Engineering Department,Texas A&M University.

This year’s proceedings meet the challenge of thehistorical value of previous proceedings. They consistof 12 technical papers presented in the Texas A&MSeminar and 17 papers in the WEDA portion of theprogramme. The customary breadth and scope of thesubjects of the papers also is continued. Some sub-jects are new; others bring contemporary results andrelevancy to some subjects on which considerable priorliterature exists. Accordingly, they fill a very importantrole in maintaining the currency of the technology ofdredging. The papers presented in each section of theproceedings are listed below.

THIRTY-THIRD TEXAS A&M DREDGING

SEMINAR

1. US – UK Cooperation on Dredging Turbidity

Modeling by N. Burt and D. Hayes2. Meeting the Competition - Upgrading the Dredge

Fleet by C. Marburg3. Tomography as a Measurement Method for

Density and Velocity Distributions by Y. Ma, S. Miedema, V. Matousek, and W. Vlasblom.

4. Data Logging in Wilmington Harbor Project by R. Ramsdell

5. Wetlands Treatment to Address Ammonia Toxicity in the Dredging Process, Bayou SegnetteWaterways, Louisiana by L. Mathies and E. Russo

6. Dredging Calculators and Screening Tools by D. Jones and J. Clausner

7. Flocculation Enhancement Technologies for theDredging Contractor - Guidelines for the Selectionof a Polymer Supplier by E. Seagren

8. Dredging Alternatives for Delivering Sand forBeach Nourishment by R. Randall and B. Koo

9. Precision Dredging to Avoid the ContaminatedSediments and the Challenges of Retaining AllWater by M. Hermans, W. Haynes, and G. Speyer

10. Numerical Simulation of a Development of aDensity Wave in a Long Slurry Pipeline by Z. Lu, V. Matousek, and S. Miedema

11. The Mechanism of Kinematic Wedges at LargeCutting Angles- Velocity and Friction Measure-ments by S. Miedema and D. Frijters

12. Application of a Combined Dredging and Veneer-Capping Remedy to Soft, Unconsolidated Sediments by T. Thompson, C. Houck, L. Brausch, S. Muttige, R. Paulson, and S. Hint.

WESTERN DREDGING ASSOCIATION TWENTY-THIRD ANNUAL TECHNICAL CONFERENCE

1. Development of Excavating by and Loading ofTrailing Suction Hopper Dredges during the LastDecade by E. Bijvoet, A. de Jager, C. Kramers, S. Ooyens, and R. Ouwerkerk

2. Demonstration of Transport and Handling ofIllinois River Sediment for Beneficial Use by J. Marlin

3. Demonstration Project on Dredging and MarshDevelopment Using a Flexible-Discharge DustpanDredge on the Mississippi River at the Head ofPasses by T. Welp, J. Clausner, D. Thompson, J. Mujica, and G. Boddie

4. Grand Calumet River Sediment RemediationProject: Larges Impacted Sediment, HydraulicallyDredging Project in North American by R.Menozzi, G. Green, T. Binsfliel, V. Buhr, S.McGee, C. Moses, S. LaViolette, and T. Blackmar

5. Remediation of Contaminated Sediment Sites:Engineering for Implementation with PilotProjects by G. Hicks and R. Traver

6. Duluth-Superior Harbor Restoration Project by R. Desrosiers, D. Gaffney, P. Olk, and D. Smith

7. Beneficial Reuse of Lower Fox River Contaminated

replaced the so-called Overland Route, and what hasbecome of this once magnificent undertaking since1956. One could call it the rise and fall and rise of theSuez Canal.

Prior to the canal’s existence, the primary route fromEngland out to Queen Victoria's India and the East wasan 84-mile sand track stretching across the dunes fromthe Mediterranean town of Alexandria, Egypt to theRed Sea port of El-Suweis. This had been built by aRoyal Navy officer Thomas Waghorn in the late 1830swhere it happily if dustily, existed for 30 years until theFrenchman De Lesseps arrived on the scene. The canal De Lesseps dug went through to the Gulf ofSuez, running parallel to the Overland Route, effectivelycompeting with it and soon putting it out of business.With Disraeli’s foresight, the British Government purchased a large portion of the canal company’sshares thus winning control of the canal — and somemight say of Egypt as well. This era was majestic andimperial while it lasted.

Clearly the author appreciates the monumental engi-neering achievement of building the Suez, as well asDe Lesseps’ powers of persuasion to unite diversepotentates to support the project. He also encouragedthousands of workers to literally put their shouldersunder it and many to give their lives for it.

Eventually, of course, Britain and France were confrontedwith an emerging post World War II resentment of“imperialism”, and in 1956 the canal was nationalisedby Gamal Abdel Nasser. For almost twenty years it laydormant and its economic importance diminished. In addition, the canal’s use has been eclipsed bycircumstances; modern ships are often too large topass through it and often now go around the Cape ofGood Hope as they did before. For all this De Lesseps’dream is still functioning and through the appearance of this book and other events such as the excellentexhibition on the Suez at the National Dredging Museumin The Netherlands (see page 24), we are forced toremember this incredible project and re-evaluate itsinternational significance. If you are interested in what ittakes to realise a project so vast, Karabell’s book shouldnot be missed.

Available from the publishers or in bookstores.

Sediments by R. Paulson, T. Carroll, and T. Baudhuin

8. Upper Mississippi River Habitat RestorationProjects by J. Janvrin, G. Green , V. Buhr, R. Perk, K. Westphall, and M. Pegg

9. Geotechnical Investigations for Dredging Projects- A Contractors View by K. Johnson andG. Sraders

10. Corps Evaluation of Fluid Mud Measurement andthe Definition of Navigable Depth by T. Welp, C. McNair, and Larry Buchanan

11. Expecting the Best and Preparing for the Worst: Early Neutralization and Claim AvoidanceDuring Dredging and Marine Construction byJ. DeRuggeris and C. Parent

12. Dredging and Dam Removal by K Kabbes13. Evaluation of Napthalene Emissions During

Dredging at the St. Louis River/Interlake/DuluthTar NPL Sie, Duluth, Minnesosta by M. Costello,H. Huls, J. Berdahl, G. Schewe, and M. Zimmer

14. Designing Borrow Pit CAD Sites: RememberNewton’s 3rd Law! by J. Germano

15. Cap Design of CAD Pits in San Jose Lagoon, San Juan, Puerto Rico by S. Bailey, P. Schroederand C. Ruiz

16. Deep Water Capping Demonstration Project atthe Massachusetts Bay Disposal Site by G. French, J. Morris, and T. Fredette

17. Equipment Selection Factors for EnvironmentalDredging by M. Palermo, N. Francinques, and D. Averett

This publication can be obtained from:Center for Dredging Studies, Ocean Engineering Program, Civil Engineering Department, Texas A&MUniversity, College Station, Texas 77843-3136, USAemail: [email protected] or

Executive SecretaryWestern Dredging AssociationP.O. Box 5797, Vancouver, WA 98668, USAemail: [email protected]

Parting the Desert: The Creation of the Suez CanalLondon, United Kingdom: John Murray Publishers Ltd,2003. New York, NY, U.S.A.: Alfred A. Knopf Inc.,2003. Hardcover.

By Zachary Karabell

In ten years time from 1859 to 1869, a visionaryFrenchman named Ferdinand de Lesseps changed theface of the Middle East. He dreamt of, and realised, a canal linking the Mediterranean to the Red Sea whichsince then, except for an interlude in the middle of thelast century, has afforded an efficient connectionbetween East and West. Zachary Karabell’s bookchronicles the development of the canal, how it


28

Seminars/Conferences/Events

29

OCEANTEX 2004NSC Complex, Mumbai, India

February 11-14 2004

Energy is essential for economic development and oiland gas play a dominant role in fueling economicgrowth. For this reason, Chemtech Foundationpresents an exhibition encompassing OffshoreTechnology 2004 (oil and gas extraction equipment;safety devices and supplies; construction andengineering equipment and services; marineequipment; field exploration); Gastech 2004 (pipelinenetwork for gas grid; LNG technology; distributionnetwork instruments); and Transport & Logistics 2004(specialised ships for LNG transport; offshore supplysevice; sub-sea and other piping); Refining 2004(catalyst systems; tanks and storage equipment); and Weldtech (submerged arc welding; laser cutting,welding machines).The conference will bring together experts from all over the world and provide a unique networkingopportunity.

For further information contact:Deepak Mukhi, Chemtech Secretariat3rd Floor, 210, Taj Building, Fort, Mumbai-400001, India tel. +91 22 563 10515fax +91 22 563 10525 email: [email protected]

INMEX KL 2004 Kuala Lumpur, Malaysia

February 24-26 2004

INMEX KL 2004 will beheld under the auspices of theMalaysian Ministry of Transport, Government ofMalaysia, International Association of Ports andHarbors (IAPH, Japan), the Eastern DredgingAssociation (EADA), Federation of Malaysian FreightForwarders, and the Malaysian National ShippersCouncil.

Exhibitors include those involved with ports and porttechnology, shipbuilding; shipyard industry, dredging,maritime and port safety equipment, shipyardinstallations and equipment, marine equipment, offshore technology, port infrastructure, material han-dling and logistics services and more.

For further information contact:Nazeeba Zarin, Deputy ManagerPDA Trade Fairs, PDA House #32/2, Spencer Road, Frazer TownBangalore-560005, Indiatel. +91 80 554 7434, ext. 226fax +91 80 554 2258www.inmexindia.com / www.inmexkl.com

International Seminar on Dredging and ReclamationUNESCO-IHE

Delft, The NetherlandsMarch 1-5 2004

The International Seminar on Dredging and Reclamation will be given in March as part of thecurriculum of the International Masters Programme inHydraulic Engineering, study branch “Coastal Engineering and Port Development” at UNESCO-IHE in Delft. In contrast to prior years, a limited number of“outside” participants will be permitted to join thismodule of the curriculum.

More than 11 years ago, the International Associationof Dredging Companies (IADC) and he InternationalInstitute of Hydraulic and Environmental Engineering,now known as UNESCO-IHE, joined forces to developthe first International Seminar on Dredging and Reclamation. The Seminar has since been heldindependently in Singapore, Dubai, Argentina andEgypt. Presented by professionals from IADC membercompanies, the Seminar forms a complete one-weekunit within a year-long postgraduate level studyprogramme at UNESCO-IHE. The Seminar has becomeone of the main elements in the IADC’s efforts toinform young people worldwide about the need for


Asia Pacific Maritime 2004Singapore Expo, Singapore

March 24-26 2004

Targeted at both the Marine Engineering and Portsindustry sectors, Asia Pacific Maritime 2004 is a uniquecomprehensive international trade and technologyexhibition, covering the full range of commercialmaritime equipment, facilities, operations and services.The exhibition is aimed at Port Authorities, ship ownersand builders, and maritime specialists.

For further information contact:Daniel Chan or Ng Chuan YongReed Exhibitions Pte, Ltd.51 Changai Business Park Central 2#07-91 The Signature, Singa6ore 480066tel. +65 6789 8800, fax +65 6789 7711email: [email protected]

Seminar on Environmental Aspects of DredgingPAO Civil Engineering and Construction

Delft, The NetherlandsMay 13-14 2004

Dredging is a necessary activity in society’s develop-ment. Under the right circumstances it is also a veryuseful tool for remedying past environmental interfer-ences. By its very nature, however, the act of dredgingand relocating dredged material is an environmentalimpact. It is, therefore, of the utmost importance to beable to determine whether any planned dredging willhave a positive or negative impact on our environment.Evaluation of environmental impact should examineboth the short- and long-term effects, as well as thesustainability of the altered environment.

This two-day Seminar gives an overview of the environ-mental aspects of dredging and state-of-the-art dredgingtechniques. Topics included are:– Players, Processes and Perspectives;– Conventions, Codes and Conditions: Marine Disposal

and Land Disposal;– Investigation, Interpretation and Impact;– Machines, Methods and Mitigation;– Reuse, Recycle or Relocate,– Effects, Ecology and Economy– Frameworks, Philosophies and the Future.

Besides presentations on these subjects, participantswill be challenged in case studies to apply the principlesdiscussed in order to get a full understanding of thescope and importance of the environmental aspects ofdredging projects, the management of dredged material,and effects of environmental guidelines.

dredging, the process by which the decision to dredgeis reached, and how a dredging project is implemented.

Those wishing to participate in the programme in Marchare urged to contact the IADC as soon as possible.Space is limited.

For further information please contact:IADC Secretariat, The Hagueemail: [email protected]

Oceanology International 2004ExCel, London, UK

March 16-19 2004

This is one of the largest and busiest internationalevents in the global marine science and ocean techno-logy fields. It has hundreds of exhibitors and attractsthousands of international visitors including policymakers, industrialists, government representatives,decision makers, researchers, directors, managers andmanufacturers involved in every aspect of oceanogra-phy. They meet to address the present and futuretrends of the industry and to view the launch of newtechnologies, equipment and services.

It is sponsored and supported by the Society for Under-water Technology, European Oceanographic IndustryAssociation, World Meteorological Organization, Intergovernmental Oceanographic Commission, The Hydrographic Society and Hydro International.

The following disciplines are representative of the scope of OI: marine environmental science; ocean observing and modeling; measurement andinstrumentation; data harvesting; marine survey andengineering; diving and ROV; navigation and remotesensing; marine pollution monitoring and control;hydrography; marine R&D; maritime defence; dredgingand coastal engineering; renewable energy; resourcesfrom the sea; marine civil engineering and more.

For further information contact:Spearhead Exhibitions LtdApex Tower, High St, New Malden,Surrey, KT3 4DQ, UKwww.spearhead.co.uk

Lesley Ann Sandbach, Conference Directoremail: [email protected]. +44 208 949 9837

Craig Moyes, Project Director email: [email protected] tel. +44 208 949 9840


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The Environmental Seminar is a joint effort of theInternational Association of Dredging Companies (IADC)and the Central Dredging Association (CEDA). It is partof the curriculum of PAO Civil Engineering andConstruction, the foundation for postgraduateeducation of the Technical University of Delft inThe Netherlands. The Seminar is aimed at consultantsin dredging related industries, and professionals fromdifferent governmental bodies such as municipalities,district water boards, ports and harbour authorities andcentral government.

Course material includes the seven book series ofGuides entitled “Environmental Aspects of Dredging”.The course fee is € 790, including these books, lecturenotes, coffee, tea and lunches. Travel costs and lodgingare not included.

For further information contact:PAO Civil Engineering and ConstructionP.O. Box 5048, 2600 GA Delft, The Netherlandstel. +31 15 278 4618, fax +31 15 278 4619email: [email protected]

29th ICCE 2004 Congress Centre of the National Civil

Engineering Laboratory (LNEC), Lisbon, Portugal

September 19-24 2004

The Organising Committee of ICCE 2004 and thePortuguese coastal engineering community arepleased to announce the 29th International Conferenceof Coastal Engineering (ICCE), continuing the success-ful conference series which is the world’s premierforum on coastal engineering and related sciences.

Original papers will be presented on theory,measurement, analysis, modelling and practice of thefollowing topics: Coastal processes and climate change; oceanography,meteorology, morphodynamics and sedimentprocesses, macro and micro tidal regimes, extremeevents, coastal waves, effects on coastalmanagement; flood and coastal defence engineeringincluding beach management and nourishment, coastal and beach control structures, constructiontechniques and performance; flood risk management;recreation, industrial activity, water quality, wetlandsand estuaries, sustainability, environmental economics;ports and harbours including siltation, dredging anddredged material re-use, navigation channels,optimisation, wave-structure interactions, breakwatermonitoring, coastal interactions; and coastal legislation,planning and cooperation.

For further information contact:ICCE 2004 Secretariat, c/o LNEC - DIEAGAv. do Brasil, 101, 1700-066 Lisbon, Portugaltel. +351 21 844 3483 or 844 3900fax +351 21 844 3014e-mail: [email protected]

World Dredging Congress XVIICCH - Congress Centrum,

Hamburg, GermanySeptember 27-October 1 2004

Every three years leading experts meet in a differentpart of the world for the World Dredging Congress(WODCON). The congress is held under the auspicesof the World Dredging Association which is comprisedof the WEDA, CEDA and EADA. In 2004 the theme ofthe conference will be “Dredging in a Sensitive Environment”. It will take place in Hamburg, organisedby CEDA on behalf of WODA, and co-sponsored by theMinistry of Economic Affairs, Free and Hanseatic Cityof Hamburg, and the Department of Port and RiverEngineering and the Shipbuilding, Machinery & MarineTechnology International Trade Fair (SMM 2004) whichwill run simultaneously.

The programme will consist of Technical Sessions withhigh quality peer-reviewed papers and a special Envi-ronment Day focussed on environmental challengesand solutions. An Academic Session, with contributionsby young scientists, continues CEDA’s support ofyoung professionals. Technical visits in and aroundHamburg, including views of the Port of Hamburg, are planned.

For further information about WODCON XVII contact:www.woda.org orCEDA, P.O. Box 488,2600 AL Delft, The Netherlandstel. +31 15 278 3145, fax +31 15 278 7104email: [email protected]

WEDA XXIV & TAMU 36 Dredging SeminarWyndham Palace,

Orlando, Florida, USAJuly 6-9 2004

The twenty-fourth Western Dredging AssociationAnnual Meeting and Conference and the thirty-sixthTexas A&M Dredging Seminar will be held in July atthe Wyndham Palace, Orlando, Florida. The conferencewill provide an in-depth technical programme based on the theme, “Unique Dredging Projects”. It providesa unique forum for discussions amongst dredgingcontractors, port authorities, government agencies,environmentalists, consultants, academicians, and civiland marine engineers.

Topics of interest include but are not limited to: dredging and navigation; dredging systems and tech-niques; new dredging equipment; surveying; costestimating; dredging and navigation; project casestudies; automation; inland dredging; contaminatedsediments; numeric modelling; geo-technical aspects;beach nourishment; beneficial uses; and wetlandscreation and restoration.

Interested parties should submit one-page abstracts tothe members of the Technical Papers Committee listedbelow. The committee will review all submissions.

Deadlines are:Submission of one page abstract: December 19, 2003Notification of authors: January 3, 2004Final manuscripts due: April 5, 2004

For further information and to submit abstracts contact:Dr. Ram K. MohanBlasland, Bouck & Lee, Inc., 326 First Street, Suite 200Annapolis, MD 21403tel. +1 410 295 1205, fax +1 410 295 1209email: [email protected]

Dr. Robert E. RandallDept. of Civil Engineering, Texas A&M UniversityCollege Station, TX 77843tel. +1 979 862 4568, fax +1 979 862 8162email: [email protected]

Mr. Stephen Garbaciak, Jr.Blasland, Bouck & Lee, Inc.200 South Wacker Dr, Suite 3100Chicago, IL 60606tel. +1 312 674 4937, fax +1 312 674 4938email: [email protected]

HYDRO4 Galway, Ireland

November 2-4 2004

The Hydrographic Society, presently devolving into theInternational Federation of Hydrographic Societies(IFHS), is to hold its 14th biennial international sympo-sium in Galway, Ireland from 2-4 November 2004.Proceedings, which will also include a major exhibitionof equipment and services, workshops, field demon-strations and anticipated visits by specialist surveyvessels, are being co-sponsored by several leadinginternational survey and maritime organisations.

The main theme of the HYDRO4 symposium is “Diversity”. The aim is to provide a forum for address-ing the use of hydrographic expertise for non-traditionalsurvey applications in new seagoing operations, whileconversely exploring potential benefits for exploitingnon-traditional survey techniques within the hydro-graphic profession itself. Related technical issues and topics will include:Bathymetry, Coastal Zone Management and Protection,Data Acquisition and Management, Electronic Charting,GIS and Positioning.

300-word English-language abstracts of proposedpapers, by disk or email in Word 2000 format, arerequired by March 31 2004. They should be submittedto the Symposium organising committee from whomfurther general details are also available.

For further information and submissions contact:Hydro474 Callington Road, Saltash, Cornwall PL12 6DY, UK tel. +44 (0)1752 843461, fax: +44 (0)1752 848267 email: [email protected]


Call for Papers

32

Africa

Ballast Ham Dredging (Nigeria) Ltd., Ikeja-Lagos, NigeriaNigerian Westminster Dredging and Marine Ltd., Lagos,Nigeria

The Americas

ACZ Marine Contractors Ltd., Brampton, Ont., CanadaBallast Ham Sucursal Argentina, Capital Federal, ArgentinaBallast Ham Dredging do Brazil Ltda, Rio de Janeiro, BrazilDragamex SA de CV, Coatzacoalcos, Mexico

Asia

Ballast Ham Dredging India Private Ltd., Mumbai, IndiaBallast Ham Dredging bv Singapore Branch, SingaporeDredging International Asia Pacific (Pte) Ltd., SingaporeHyundai Engineering & Construction Co. Ltd., Seoul, KoreaJan De Nul Singapore Pte. Ltd., SingaporeTOA Corporation, Tokyo, JapanVan Oord ACZ B.V., Dhaka, BangladeshVan Oord ACZ B.V., Hong Kong, ChinaVan Oord ACZ B.V., SingaporeVan Oord ACZ Overseas B.V., Karachi, Pakistan

Middle East

Boskalis Westminster M.E. Ltd., Abu Dhabi, UAEGulf Cobla (Limited Liability Company), Dubai, UAEJan De Nul Dredging, Abu Dhabi, UAEVan Oord ACZ Overseas B.V., Abu Dhabi, UAE

Australia

Ballast Ham Dredging Pty. Ltd., Brisbane, QLD, AustraliaDredeco Pty. Ltd., Brisbane, QLD., AustraliaVan Oord ACZ B.V., Victoria, NSW, Australia

Europe

ACZ Ingeniører & Entreprenører A/S, Copenhagen, DenmarkA/S Jebsens ACZ, Bergen, NorwayAtlantique Dragage S.A., Nanterre, FranceBaggermaatschappij Boskalis B.V., Papendrecht, NetherlandsBallast Ham Dredging bv, Rotterdam, NetherlandsBallast Ham Dredging Ltd., Camberley, United KingdomBallast Ham Nederland bv, Gorinchem, NetherlandsBoskalis B.V., Rotterdam, NetherlandsBoskalis International B.V., Papendrecht, NetherlandsBoskalis Westminster Aannemers N.V., Antwerp, BelgiumBoskalis Westminster Dredging B.V., Papendrecht, NetherlandsBoskalis Westminster Dredging & Contracting Ltd., CyprusB.V. Bedrijfsholding L. Paans en Zonen, Gorinchem,Netherlands

Draflumar SA., Neuville Les Dieppe, FranceDRACE (Grupo Dragados S.A.), Madrid, SpainDravo S.A., Madrid, SpainDredging International N.V., Zwijndrecht, BelgiumDredging International (UK), Ltd., Weybridge, United KingdomHeinrich Hirdes GmbH, Hamburg, GermanyJan De Nul N.V., Aalst, BelgiumJan De Nul Dredging N.V., Aalst, BelgiumJan De Nul (U.K.) Ltd., Ascot, United Kingdom

Mijnster Beheer B.V., Gorinchem, NetherlandsN.V. Baggerwerken Decloedt & Zoon, Oostende, BelgiumSociedad Española de Dragados S.A., Madrid, SpainSodranord S.A.R.L., Le Blanc-Mesril Cédex, FranceTerramare Oy, Helsinki, FinlandTideway B.V., Breda, NetherlandsTOA (LUX) S.A., Luxembourg

Van Oord ACZ B.V., Gorinchem, NetherlandsVan Oord ACZ Ltd., Newbury, United KingdomWasserbau ACZ GmbH, Bremen, GermanyWestminster Dredging Co. Ltd., Fareham, United Kingdom

Membership List IADC 2003Through their regional branches or through representatives, members of IADC operate directly at all locations worldwide.

International Association of Dredging Companies

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