punch techpaper foynes port west jetty (1)

7/29/2019 PUNCH TechPaper Foynes Port West Jetty (1)

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Figure 1

1.0 INTRODUCTION

1.1 Foynes Port

Foynes Port has traditionally been a

commercial port to all sea-going vesselswishing to service the west coast ofIreland. Over the past twenty-five yearsthe port has grown such that in the earlynineties, Foynes Harbour Trusteesrecognised the need to develop a moderndeepwater facility capable of handlingvessels up to Panamax size.

Over that time the port was usedboth for export of goods such as frozenmeat, bagged sugar, milk powder, andore materials barytes, lead and zincconcentrate and for import of bulkgoods such as coal, animal feed,

fertilisers, general cargo, molasses andoil products.The berthage available consisted

primarily of the East and West Jetties.The existing West Jetty, 106 metres long,handled vessels up to 22,000 DWT, butwas limited in its load carrying capacity,as it was maintained dredged to a level of10.15m OD (Poolbeg). The East Jetty,296 metres long, was capable of handlingvessels up to 35,000 DWT, which wasmaintained dredged to a level of 11.3mOD, i.e. below Mean Low Water Springs.

The bulk liquids berth consists oftwo dolphins linked to the shore, and was

constructed in 1992. This availableberthage also included 140 metres of

shallower berthage at the West Quay,which could handle vessels up to 6,000DWT at suitable tides.

1.2 New Deepwater Facility

Foynes Harbour Trustees,recognising the need to progress thedevelopment of the port, madeapplication in 1993 under the NationalDevelopment Plan to the Department ofthe Marine and Natural Resources tocarry out works to extend the handlingcapability of the port by construction ofnew jetty facility, dredging, and provisionof port related infrastructure. Theseproposals were subsequentlyincorporated in the commercial seaportsmeasure of the EU OperationalProgramme for Transport 1994-1999.

The steady growth in port trafficfrom typical 660,000 tonnes handled in1983 to 1,275,000 tonnes handled in1993 indicated the need for thedevelopment. A pre-feasibility study wascommissioned in 1995 by FoynesHarbour Trustees to determine theoptimisation of the proposeddevelopment. This study formed thebasis of the new work incorporating thedeepwater facility.

1.3 History

Foynes Harbour, having a goodsheltered location from heavy seas and

ground swell, has been an importantharbour for many years.

The earliest harbour works ofimportance were begun in 1846 with theconstruction of a masonry wharf 83metres long and 12 metres wide in thelocation now known as the West Quay.

The cost of these works wasessentially funded by Lord Monteaglewhose family has long been associatedwith Foynes.

The Foynes Harbour Trustees wereformed in 1890 and they immediatelyconstructed a short timber jetty ongreenheart piles running from the end ofthe masonry pier. This timber structurewas later removed in 1934 to make wayfor the new West Jetty.

A spur from the foreshore at theeastern end was constructed in 1915. It

was 46 metres long and 5.5 metres wideand consisted of cast in-situ concretebeam and slab placed over precast pilesand precast concrete walls. Thisstructure remains in place today in goodworking order.

The West Jetty structure wasconstructed in 1936 to service vessels upto 8,000 tonnes displacement and 7.6metres draught. This was a concretestructure founded on precast concretepiles driven to firm stratum in groups, withcylindrical heads filled with in-situconcrete at the top of the pile extending

through a splayed concrete pile cap to in-situ flat slab concrete deck.

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This structure was upgraded as part ofthe new works.

Further berthing facilities wereprovided in 1968 when the first elementof the existing East Jetty, 144 metreslong, together with concrete accessviaduct was provided, followed by an

extension of 155 metres in 1984 tocomplete this jetty. The dolphin systemto enable import of oil and chemicals wascompleted in 1992.

Under the Harbours Act 1996,Foynes Harbour Trustees was replacedby Foynes Port Company in March 1997.The extent of the jurisdiction of the portwas determined and this enabled anoverview to be taken on the capital worksprogramme relating to future marineinfrastructure.

2.0 DESIGN APPROACH2.1 Pre-Feasibility Study

The pre-feasibility studycommissioned by Foynes HarbourTrustees in 1995 was carried out by H RWallingford Limited. It addressed fourmain aspects:

Alternative jetty layouts, forms ofconstruction and costs

Analysis of trade and berthoccupancy to assess future demandfor berthage

Desk studies on navigation andrequirements for navigation channelsand turning areas

Examination of siltation risks basedon desk studies and fieldmeasurements

(i) It was confirmed that theproposed layout suggested by the portwas feasible from an engineering point ofview. Ideally filling should be right up tothe back of the quay to maximise accessbut ground conditions subsequentlyprecluded full implementation of this.Alternative structural forms were

examined.

Based on the pre-feasibility study,Michael Punch & Partners initiated apreliminary design review of the proposalfor the new development in consultationwith Foynes Harbour TrusteeManagement in 1995. Studies of thescope of the works required to bring theproject to completion were undertakenand decision made as to the sequence

and the extent of the works.Sheet pile quays were impractical

because of the presence of unsuitableground (soft silts overlying boulder clayand rock).

Serious consideration was given togravity structures block-work walls andcaissons but it was concluded that theunevenness of the underlying strata, plusthe need to remove soft silty material toprovide adequate foundations made themimpractical. Sites for construction andlaunching caissons were also notavailable conveniently.

An open piled deck was thereforeselected supported on tubular steel piles.A standard design loading of 25 kN per

square metre was initially considered.However, port experience on the EastJetty with the flexibility for crane loadinggiven by a higher design capacity of 75kN per square metre meant that thiseventually prevailed.

(ii) The berth occupancy studiesshowed that the East Jetty was the mostheavily used facility and that, if tradeforecasts were correct, additionalberthage in addition to the proposedextension of the West jetty would berequired within the time frame 2001 to2005. These predictions of pressure foradditional berthage are already beingconfirmed in practice.

(iii) The navigation study concludedthat the size of the navigation channeland turning circle were below PIANC

recommended standards. In particular,the constraint at Barneen Point wouldrequire attention by dredging and landremoval. The study also concluded thatnavigation aids should be improved in theport and in the East Channel so thatvessels leaving the port could use them.

(iv) Siltation in the port was shownpredominantly to be caused by the ebbtide through the harbour and it wasconcluded that the new berth at the WestJetty would have some increase on themaintenance dredging commitment.Flow and siltation modelling studies wererecommended for the port and itsapproaches.

2.2 Project Planning

Decisions were taken as follows:

Set up a flow model of the port andcarry out siltation monitoring prior tocompleting navigation to determinethe best option for new approach tothe upgraded berths.

Carry out the jetty constructionworks as a single contract includingany ancillary works such asinstallation of new navigation lights,landing stages for small craft using

the port, and provision of supportbuildings.

Complete the works with a separatedredging contract.

2.3 Navigation Studies

Following receipt of tender submissionsfrom a number of hydraulic specialists,

in 1996, H R Wallingford Limited werecommissioned by Foynes HarbourTrustees to carry out Navigation Studiesof the port approaches and within theinner port area so as to fine tune theproposals for the new West Jetty and theassociated capital dredging works. Aswell as setting up a port model, a numberof real-time simulations were carried outat H R Wallingfords premises in UKusing the H R Mardyn simulator. FoynesHarbour Trustees pilots participated insimulation exercises to ensure that theywere satisfied with the results.

The results of these studies wereused to:

(a) Assess the projected rates ofsiltation arising within the Harbour.

(b) Determine the optimum dimensionsfor vessel manoeuvrability inrespect of both daylight and nighttime navigation.

(c) Establish the new approachchannel to the port and therebydetermine the extent of dredgingnecessary to achieve these definedareas.

(d) Confirm the appropriateness ofnavigational aids, particularly atnight.

Conscious of the need to set up the portmodel correctly and to determine theoptimum manoeuvres, significant timewas allowed to carry out the fieldworkand subsequent analysis prior to issue ofreport. The results obtained were thenused to determine the extent of theCapital Dredging Works to conclusion.

2.4 Jetty Design Concept

An integrated Design Teamapproach was adopted from an earlystage of the project design. Togetherwith Michael Punch & Partners as TeamLeaders, H R Wallingford Limitedspecialist marine consultants advised onthe fundamental design elements, andHealy Kelly & Partners CharteredQuantity Surveyors were retained asquantity surveyors.

Conceptual design on the new jetty

commenced in 1995. Initially a view hadto be taken on the existing West Jettyand in particular its further design life.

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A desktop study of old drawings and sitedata in the possession of FoynesHarbour Trustees was carried out.Preliminary calculations were made onthe adequacy of the structure and a viewtaken on its load carrying capacity. Inthis instance the Paper on the New

Deep-Water Jetty at Foynes, CoLimerick by H A Delap and T ASimington published in 1938 by theInstitution of Engineers of Ireland wasmost helpful.

The clients brief called for extensionof the existing West Jetty eastwards for adistance of 164 metres and an upgradingof the existing jetty. With respect to theexisting structure, it was considered thata load test on single pile unit be carriedout to verify load carrying capacity. Aftersome investigation, it was agreed that

such check would be too onerous andwould require significant opening up anddestruction of existing structure.

A design decision was taken toignore the structural support provided bythe existing West Jetty in any newscheme. It was therefore decided to pilethrough the existing deck and to cast anew in-situ flat slab supported as atemporary works measure off the existingdeck but designed to span onto the newpiles.

It was also decided to includeancillary works such as provision of twonew landing stages for small craft on themainland in lieu of the existing landingstage being made obsolete by the newconstruction. This work also includedprovision of new landing stage at FoynesIsland.

The jetty is designed to take a35,000 DWT bulk carrier vessel fullyladen or a partly laden vessel of 45,000DWT. The jetty length of 270 metres issuch that it can accommodate both a35,000 DWT vessel and a 22,000 DWTvessel simultaneously.

2.5 Dredging

The design approach to the scope ofthe dredging works was determined bythe requirements of Foynes PortCompany to provide deepwater berthingfor larger vessels at all stages of the tide.In particular, the design dredge levels to 12.0 m OD in the berths and to 8.1 mOD elsewhere in the inner port area wererequested at an early stage.

Studies were carried out on theapproaches to the berths and on turning

circles within the inner port area, and thelimit of the dredge was determined. Thisdredge limit was then verified or modifiedas appropriate when the real timesimulation studies were carried out.

2.6 Operational Issues

Arising from the signing off of the designcriteria, the following operational issueswere determined:

The port is capable of handlingvessels up to Panamax size partlyladen subject to dimensional checkson vessel.

The limit of size of vessel is sodetermined by the ability to swing thevessel within the inner port area.

The maximum size of vessel whichcan be handled following thecompletion of the development is:

Length 204 mBeam 29 mWorking draught 10.5 m

The live load capacity of the newjetty is 75 kN per sq metre. This providesfor operation of large mobile cranes atany position on the new jetty.

3.0 PRELIMINARY DESIGN

3.1 Overall Design Considerations

The new West Jetty structure isdesigned as two independent structures.One structure forms the extension to the

east while the other occupies the area ofthe old West Jetty. This is primarily dueto the difference in site conditionsbetween the two elements, as work overwater and work from a solid platformrequire different design approaches.Another important reason for theincorporation of independent structureswith separate construction phases, is theclients requirement to have use of asmuch of the available quayside facilitiesas possible during construction. Theworks were therefore set out on a phasedbasis to enable partial hand-over to takeplace midway through the contract.

The phase 3 element of the newWest Jetty is a marginal quay structureand occupies the western 106 metres ofthe new jetty, while the remaining 164metres is offshore and accessed from thewest by the marginal quay and from theeast by a new concrete viaduct.

Figure 2

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The phase 2 jetty extension is givenlateral support at the west end by agroup of raking piles. The extension isgiven lateral support at the east end fromraking piles on the land-ward end of theconcrete viaduct. The jetty deck spanshorizontally between these two strong

points to resist any applied horizontallateral loads. The phase 3 jettyupgrading is given lateral support alongthe central 70 percent of its length alsoby raking piles. Applied horizontallongitudinal loads are resisted throughportal action of all 102 no. piles in phase2 and 69 no. piles in phase 3.

3.2 Load Conditions

As discussed in item 2.1 above,the design loading for the deck wasestablished as a characteristic imposed

blanket loading of 75 kN per Sq metre.This loading relates to the deck areanearest the berth for a distance ofapproximately 18 metres from the berth.

The open tidal basin at the rear ofthe existing West Jetty was designed tobe filled with a structural deck, which hasa characteristic imposed load capacity of35 kN per Sq metre. The access viaductat the eastern end of the new extensionalso has a characteristic imposed loadcapacity of 35 kN per Sq metre. Thehorizontal characteristic berthing load onthe structure is 2000 kN when transferredthrough the fender system, andcharacteristic bollard loads are 1000 kN.

3.3 Preliminary Design Layout andSizes

The structure is designed to maximisethe use of precast concrete elements toprovide a permanent shutter and workingplatform for insitu works while minimisingthe amount of temporary works overwater.

The structure of the extension at theWest Jetty is designed as a compositeconcrete three-span deck spanning

continuously between support beamsrunning longitudinally along the length ofthe extension. The beams are at6.39 metre centres. The concrete deckis 550mm thick consisting of 200mmsolid precast pre-stressedconcrete slabstopped with 350mm of insitu reinforcedconcrete. The entire deck is at agradient of 1:100 for drainage.

The support beams are alsodesigned as a composition of precastand insitu concrete and span betweenpiles driven at 7.62 metre centres alongthe line of the beams. This dimensional

grid was determined by the spacing ofexisting piles at the old West Jetty.The precast beams are 1500mm wide

and 850 mm high and span from pile topile. Insitu pile caps connect the beamsand transfer the loads to the pile. Thefull slab depth of 550mm over the beamsis incorporated in the composite designof the beams. The piles are 1067mmoutside diameter, with a wall thickness of

25mm.The access viaduct to the eastern

end of the extension, and the old westbasin infill slab are also of compositeconcrete construction.

4.0 PROJECT PLANNING

4.1 Planning Permission and EIS

Planning permission was soughtfrom Limerick County Council in mid1996 for the development worksproposed. The application was

accompanied by an EIS.

Figure 3

The scope of the EIS includeddetailed examination of theenvironmental effects arising during theconstruction period. Sediment analysisthat had heretofore been carried out forprevious dredging works, were reviewedand used as a baseline for input into EIS.

Observations were made by third partiesduring the planning period.

Planning permission for the workswas issued in January 1997 with 7 no.conditions attaching.

4.2 Foreshore Lease

Prior to the submission ofapplication for Foreshore Lease for theJetty Works, detailed discussions wereheld with the Department of the Marineand Natural Resources. The lease wasduly issued in December 1997 prior to

the main works proceeding.

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Figure 4

4.3 Site Investigation

Simultaneous with the detail designwork, a site investigation contract wasput in place over the period June toSeptember 1996.

The investigation consisted of shell-and-auger and rotary core test holesusing NQ (Samples of 57mm diameter)and HQ (Samples of 64mm diameter)rigs from floating pontoons, and a PQ rig(giving 87mm samples) working from theexisting jetty deck. Core samples weredifficult to obtain, as recovery was poorarising from poor quality rock.

It was confirmed at an early stagethat the site covers a geological faultzone, so extra trial borings were made todetermine the extent of the anomaly.This fault was in the form of a buried

valley in the area midway along thephase 2 jetty extension. A sand depositwas found at depth in this valley. Thegeneral pattern of the stratum recordedwas silt, overlaying clays with boulderson to a very poor mudstone rock.

The investigation also revealed thatthe piles to the existing West Jetty werefounded on boulder clay at the east end,and not on rock as thought at the time ofdriving these piles.

The interpretative report and coringstaken were reviewed in detail by thedesign team prior to issue of tender

documents. Also the tenderingcontractors were invited to examine thesamples on site.

4.4 Tendering for Jetty

The tendering process was tocomply fully with Council Regulations(EEC) 2082 / 93 and 2083 / 93. It wasdecided that the method of procurement

of the project was to invite applicationsfrom contractors for inclusion in atendering short list. A contractor pre-qualification notice was published in theOJEC in May 1997.

A total of twelve applications werereceived from which seven contractorswere selected and issued with full tenderdocuments on 2

ndJuly 1997. Tenders

were received from each of thecontractors on 1

stSeptember 1997. After

reporting to Foynes Port Companyfollowing the opening of tenders, areduced scope of works was determined

and a decision was taken in December1997 to award the jetty works contract toAscon Limited.

4.5 Jetty Contract

The contract commenced on 2nd

February 1998. Whilst the contractduration called up in the tenderdocuments specified a contract durationof 82 weeks, the contractors programmestated a 52 week completion. Theconstruction programme over-ran by 7weeks from a time very early in the

contract, due to difficulties encountered inpiling in April and May 1998. Thecontractor, however, continued working

to the contractual programme andsubstantially completed the contract withthis 7 week over-run. Some extra workswere incorporated in the contract at theconclusion of the works, which extendedthe contractors duration on site. The

contractor demobilised from site for themain works in September 1999.

5 DETAIL DESIGN &CONSTRUCTION

5.1 Jetty Pile Design

The agreed design approach for thefounding of the tubular piles was toprovide open ended tubular piles drivento the firm fluvio-glacial till (boulder clay)or sedimentary mudstone rock. Suchpiles perform and are designed to reach

their working capacity by forming a plugwithin the shell core when driven throughboulder clays. The appropriate scheduleof pile lengths was drawn up on thebasis of penetration into the boulder clay(6 x pile diameter) in accordance with theAPI code.

5.2 Pre-Compression LoadTesting of Piles

A number of pre-compression pileload tests were carried out prior to drivingthe permanent phase 2 and phase 3

tubular piles. The design loadrequirement for the new

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construction is 75 kN per Sq metre whichgenerates a working pile load of 550tonnes. It was found during the tests thatthe boulder clay could not sustain thisload and the full test load was notattained. Further investigation of theboulder clay revealed the presence of the

geological fault such that the depositswere of a much coarser nature thanoriginally determined during the initial siteinvestigation.

After review of the information fromthe test piles and the furtherinvestigation, a decision was taken toprovide concrete plugs in the toe of thepile so as to enhance the load carryingcapacity of each pile. The piling wasthen carried out in a satisfactory mannerand no undue difficulties were found inobtaining the necessary pile set. Theweak sedimentary nature of the

mudstone bedrock (UCS below 5000 kNper Sq metre) meant that the piles were,in some cases, driven beyond their

Figure 5

design length which necessitated anextension and re-driving of the pile toobtain the required design pile set.

5.3 Pile Types

The tubular piles for the support of

the jetty deck are 1067mm outsidediameter 25mm thick. There is acorrosion allowance on the wallthickness - without cathodic protection orprotective coatings - for a design periodof 50 years. This corrosion allowance isbased on British Steel recommendedcorrosion allowances for a marineenvironment. The grades of steel usedare API grade X60 / X65, which satisfythe requirements of BS10025 gradeS355 GP (Grade 50).

At the toe of many of these piles aclosed-ended shoe was fitted. A method

of transferring the large driving forcesfrom the shoe to the steel wall of the pilein a suitable manner needed to bedevised. The method used was to inserta plug of concrete within the bottom2500mm of the pile prior to pitching.

In order to transfer the loads fromthe concrete plug to the wall of the pile,mild steel shear connectors in the form of50mm square bars were welded to theinside wall of the pile prior to installationof permanent shutters. The cavity wasthen filled with the concrete mixincorporating admixture to reduceshrinkage of the concrete. This helped togive an intimate bond between the faceof the concrete and the wall of the pile,improving the shear capacity of the shoewithin the pile.

Non Destructive Testing of pilematerial was carried out usingradiographic and ultrasonic methodsbefore sign-off of pile fabrication weldscarried out both on-site and in thefabrication works in Middlesbrough.

Precast concrete piles 350mmsquare in section were driven at a rakeof 1:3 at the bank-seat on phase 3 of the

work to support the bank-seat andstabilise the phase 3 deck under lateralloads. No tension is developed in thesepiles under lateral loading due to theweight of the deck overhead.

356 x 406 634 kg/m steel H pileswere driven for the fenders in the mainberths and in the return berths on thewestern side of the jetty. These pileswere designed as cantilevers from theunderlying stratum. Independentspecialist verification of the agreed pilesize was provided by the contractor for

the fender piles.

Figure 6

5.4 Piling

The large tubular piles were drivenby Delmag D55 and Delmag D62 dieselpiling hammers. These were operated ona flying leader from a 150 tonne trackedmobile crane located on the shore orfrom a large floating barge, the Marlin,equipped with fixed leader. This barge is60 metres in length and 23 metres inwidth and was also used to position thefirst precast concrete beams. TheAscon 5 barge was also used in thelatter stages of the project.

Based on the test driving monitoredduring the pile tests, the tubular pileswere driven to a set of 35 blows for50mm. This set was generally achievedin a single set-up. However, some pileshad to be re-driven after a period, inorder to verify the set.

5.5 Pile Caps

At each pile head, a method oftransferring the large forces from theconcrete to the steel wall of the pile in asuitable manner needed to be devised.The method used was to create a plug ofconcrete within the pile for the top1250mm. A permanent shutter wasslung from the rim of the pile.

In order to transfer the loads fromthe concrete plug to the wall of the pile,mild steel shear connectors in the form of25mm square bars were welded to theinside wall of the pile above thepermanent shutter. This gave the edgesof the concrete plug sufficient bearingarea to transmit the loads safely anduniformly to the wall of the pile and downto the bearing stratum. This element ofthe pile cap was usually cast only when

the upper element between the precastbeams was also ready for casting.

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Figure 7

In some cases, where the pile heads

were out of position, increasing the pilecap dimensions to encompass the pilehead accommodated the piles.

5.6 Precast Beams Phase 2

The deck spans between reinforcedconcrete beams. The beams wereprecast on site in a precast yard set upby the contractor within 200 metres oftheir final position. The beamdimensions were 1500mm wide and850mm deep, so chosen to facilitatetolerances in the pile locations afterdriving.

The grade of concrete used was42.5N20 with minimum cover toreinforcement of 65mm. This designcomplies with Table 3.4 of IS 326, Part 1.The two critical design criteria wereultimate limit strength and crack widths.The maximum crack width under fullimposed loading is 0.29mm.

The beams were cast to fit betweenthe pile heads and had two steel beamsextending from each end to allow thebeam to be rested on the top of the pilewhen cut-off to the required level. Theconcrete beams had the ends and top

surface treated to expose the aggregate

Figure 8

and give the beam a good bond with the

insitu concrete, which would later be castover it.

The steel beams extending from theends of the concrete beams wererequired to carry only the weight of thebeams alone in the temporary condition.Before the precast deck slabs could beplaced on the beams, the upper portionof the pile cap was poured between theends of two opposing beams over asingle pile. The reinforcement projectingfrom each beam would lap with thecorresponding reinforcement from theother and, when cast, the pile cap wouldform a continuous beam running thelength of the jetty extension.

Vertical reinforcement projected fromthe top of the beams to tie intocorresponding reinforcement that wouldlater be placed within the insitu slab. Inthis way the down-stand beam actedcompositely with the slab and utilised thefull depth of the beam/slab combinationto minimise the effect of bending momenton crack widths and ultimate limit statedesign.

Figure 9

Further beams were installed parallelto the span of the deck slabs at 22.86metre centres for the purpose ofstiffening the deck as a whole when thedeck slab is under lateral loading andspanning horizontally as a deep beambetween the strong points at either end.

5.7 Insitu Beams

Some beams located on the grid-line nearest the berth could not beconstructed in precast concrete due totheir larger size. This size is due to thepresence of large fenders at 22.86 metrecentres along the berth, offset ship-wardof the cope-line by approximately1300mm. The soffit level of thesebeams is 1100mm below that of theprecast beams on either side. As a

result these beams were constructed ininsitu concrete. This work necessitateda substantial amount of temporaryworks, much of which was below highwater, and thus accessible only forseveral hours each day.

5.8 Deck Slabs Phase 2

With the beams cast in position overthe piles, the precast deck slabs werelowered into position on the beams. Theprecast deck slabs were fabricated off-site by Banagher Concrete at their worksin Co. Offaly. The grade of concreteused was 60N20 with minimum cover toreinforcement of 50mm.

The precast slabs were solid slabs5250mm in length, were 200mm inthickness and were pre-stressed using 12no. cables of 12.9mm diametersuperstrand giving a total pre-stressingforce of 1674kN per slab. Reinforcementextended from the top of the slabs in theform of T10 open links. These links wereused to tie to the reinforcement at the top

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Figure 10

of the composite slab in the insituconcrete topping.

The width of the bearing shelfprovided on the precast beams on eachside was 180mm. Over the 200mmprecast deck slabs, a concrete topping of350mm was poured to complete the deckconstruction. The grade of concrete usedwas 42.5N20 with minimum cover to

reinforcement of 65mm.The precast deck slabs are designed

to support the weight of the wet concretetopping in the temporary constructioncondition. The composite section is thenavailable to resist imposed loading. Suchanalysis must take into account,however, the stresses already locked intothe precast member under loading fromwet concrete.

5.9 Bank-seat Beams

The bank-seats are reinforcedconcrete beams poured in situ on theforeshore to provide a line of support fora series of parallel T-beams which spanfrom the foreshore onto a correspondingline of support on the outer suspendedstructure, called the jetty-seat.

The bank-seats are located onphase 2 at the eastern viaduct and alsoon phase 3 on the basin in-fill deckbehind the area of high strength jettydeck.

In each case the bank-seat forms astrong point for stabilising the jetty as awhole against lateral loads such asberthing or mooring loads.

In phase 2, the bank-seat sits on 8no. 473mm outside diameter steel tubular

piles. The piles are raked at a pitch of1:3 to provide lateral stability. The rakingpiles are augmented by a down-standreinforced concrete skirt, which runs thefull length of the bank-seat beam andresists lateral movement of the jettythrough the build-up of passive pressurewith the surrounding soil. The weight ofthe TY7 bridge beams that span onto thebank-seat ensures that even underabnormal berthing forces, the pilesremain firmly bedded into the shallowrock.

In phase 3, the bank-seat issupported on a line of raking precastpiles. The weight of the TY7 bridgebeams ensures that no tension developsin the piles even under abnormal berthingforces.

5.10 TY7 Precast Bridge Beams

The TY7 precast bridge beams were

fabricated off-site by Banagher Concreteat their works in Co. Offaly. The grade ofconcrete used was 60N20 with minimumcover to reinforcement of 50mm.

TY7 bridge beams are precast pre-stressed inverted T beams normally usedfor bridge spans. They are used in thisproject to allow heavy vehicularmovements to and from the main jettydeck. The T beams used were up to 17.5metres in length and were pre-stressedusing 35 no. cables of 12.9mm diametersuperstrand giving a total pre-stressingforce of 4882.5kN per beam. The

individual beams were 750mm wide and750mm high overall.

28no. beams are located on phase 2at the eastern viaduct and 94no. onphase 3 on the basin in-fill deck behindthe area of high strength jetty deck. TheT beams are used for bridging the longspans necessary to reach the jetty fromthe foreshore, minimising the need for

intermediate supports.As discussed, the TY7 beams also

serve to provide lateral stability to thestructure as a whole under conditions oflateral loading, through their ability totransfer the lateral loads from the point ofapplication of the load at the berth, backto the raking piles at the rear. The jetty-seat beam connection with the TY7beams is designed as a continuousconnection. The connection wasdesigned to resist the high bendingmoments attracted from such a long spanunder imposed loading.

The TY7 beams are placed side byside, with each additional beam adding750mm to the width of the compositeslab. The beams are constructed withopenings at corresponding centres alongtheir length to facilitate the threading ofreinforcement through the beams to beencased in the insitu topping and tie theentire slab together. The overall depth ofthe composite slab is 850mm.

The holes nearest the ends of the Tbeams are placed such that they alignwith each other within the reinforcementcage of the bank-seat and jetty-seat,improving the robustness of the structure.

5.11 Flat slab Phase 3

The presence of an original deckover much of the phase 3 area providedthe opportunity to save costs by utilisingthe original deck where possible for useas a permanent shutter to the newconcrete deck.It was decided to use a flat slab designwhere the interference with the

Figure 11

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Figure 12

original deck structure would be limited tothe locations of piled supports spaced ata 7.62 metre by 5.6 metre grid.

Due to the uneven surface of theoriginal deck, and the gradient appliedacross the new deck for drainagepurposes, the thickness of the flat slabvaries from 400mm to 650mm. Theloading on the flat slab was such that itnecessitated the use of substantial shearlinks at pile head locations.

5.12 Fenders

The fender system is required toprevent damage to the berthing vesseland the jetty structure. It does thisinitially by presenting a large surface areafor contact with the ship. This serves tolimit the pressure exerted on the hullduring berthing to 30 tonnes per Sqmetre. The fender panel size adopted toachieve this was 6.7 metres high, 4.75metres wide, and 1.0 metre deep. Thissize was determined to an extent byreference to existing fenders within theport, which have been operatingsuccessfully for many years.

Secondly, the berthing energy of thevessel is absorbed and channelled awayfrom the point of contact in a controlledmanner through the use of rubber cellfenders located between the fender paneland the jetty deck.

Initially, it was thought that dropcantilever facing panels with energyabsorbing cell fenders behind would beacceptable. However, taking intoaccount previous port experience, it waseventually decided that the robustness ofhaving the fender panels supported

directly on fender piles would bedesirable.

The configuration eventually adopted isshown in section in figure 14 andinvolves each fender having a facingpanel of concrete with rubbing facingstrips of very low friction ultra highmolecular weight polyethylene (UHMW Pe).

Each 6.7 metre by 4.75 metre panelis supported on three no. heavy-duty(634 kg/m length) Universal Column steelH section piles which also absorb someof the energy on vessel impact. The pilesare driven to a depth that enables them

to be restrained against bending at theirtoe and to support their self-weight andthe weight of the concrete fender panel.However the founding levels aresignificantly higher than for the main steel

Figure 13

tubular piles.Each panel is braced against the

deck by two 1200mm-diameter cellfenders that compress on vessel impactto absorb the energy of the vessel. Therubber cell fenders can compress towithin 60% of their uncompressed length,

and apply a gradually increasing load ofup to 200 tonnes to the jetty deck, underberthing conditions. The energy capableof being absorbed by each fender panelis 85 tonne metres. The cell fenderswere manufactured in Korea by KumNam Chemicals Inc.

Despite the presence of low frictionfacing on the fender panels, a frictionload may develop at the contact facebetween the fender panel and theberthing vessel, and must be consideredin the design of the fenders. If theberthing vessel has a component of

velocity parallel to the line of the quay,the fender panel in contact with the hullis, to a certain extent, pulled in the samedirection. To limit the deflection of theconcrete panel, it is surrounded byconcrete thrust blocks, which resistfurther panel movement. The nominal at-rest gap between the concrete panel andthe thrust blocks on either side is 75mm.

The fender panel consisted of thebottom portion of the panel, which wasprecast on the foreshore, and the upperportions, which were insitu.

The precast portion incorporatedthree hollow shafts running the full heightof the unit to allow it to be lifted intoposition over the three vertically driven Hpiles.

The precast panel was secured in

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Figure 14

position by filling the space between thefender piles and the inner face of thehollow shafts with insitu concrete. Mildsteel shear connectors in the form ofsquare bars were welded to the fenderpiles to allow the transfer of load from theprecast panel to the fender pile. Theshear connectors were designed to carrythe load from the second lift of insituconcrete. Further shear connectors werewelded to the pile prior to pouring insituconcrete, to distribute the load in the longterm.

The very low friction ultra highmolecular weight polyethylene facing

panels were fixed to the concrete fenderby proprietary anchors cast into theconcrete at 410mm centres. The facingswere fitted with chamfered edges tominimise the likelihood of vesselsremoving the panels.

The two 1200mm diameter energyabsorbing cell fenders were similarlyfixed to the concrete elements usingproprietary anchors cast into theconcrete, using a template to ensureproper alignment.

5.13 Quarry Fill / Rock Armour

The quarry run limestone rock-fill for theproject was sourced within the port landsapproximately 1 kilometre from the site.Rock armour material was also sourcedfrom this location and used to protect theforeshore behind the West Jetty and atthe eastern and western landing stages.

5.14 Bollards

32no. 100 tonne twin bitt D baseone-piece cast iron Bean bollards Type11-10-A-40 are fitted to the West Jetty forthe mooring of vessels. They are fixed to

the deck of the West Jetty via anarrangement of cast-in grade 8.8 bolts,7no. 64mm diameter and 2 no. 28mmdiameter.

5.15 Water main / Fire main

Separate water main and fire mainare provided on the West Jetty. Thewater main is located under the jetty deckclose to the berth where it is primarilyused as vessel supply. The fire main islocated further back under the jetty deck.

Both systems comprise of closed loop

supply networks connected to existingport systems.

The water main is 100mm diameterand fire main is 150mm diameter. Bothsupplies are provided under the jettydeck through ductile iron pipes, which arecement lined and bitumen dipped with

spigot and socket connections.

5.16 Oil pipeline

The West Jetty incorporates a facilityfor loading heavy fuel oil from suitablevessels for the benefit of a port operator.To maximise the flexibility of the use ofthe West Jetty, there are two loadingstations provided, located approximately50 metres from each end of the jetty.

Due to the viscous nature of theliquid using the pipeline, it is heated priorto loading to reduce its viscosity. As the

required temperature may be as high as80 degrees Celsius, it was necessary toincorporate a number of expansion jointswithin the pipeline. These expansionjoints were designed to allow the use of apigging process, without risk of snaggingof the rubber pig within the line.

5.17 ESB Substation / Lighting

The West Jetty is automaticallyilluminated in the hours of darkness by 8no. galvanised steel lighting masts, eachwith an assembly of high powered lampsattached to the top and directed to give auniform level of illumination throughoutthe working areas. The average level ofillumination achieved on the jetty deck is50 Lux. The lighting masts are protectedfrom damage by vehicular traffic by largeconcrete bases, which rise 2 metresabove ground level.

A new electricity sub station built inthe vicinity of the West Jetty under thecontract services the lighting masts. Thissub station has capacity to be upgradedin the future to service the growing needsof the port and its users.

5.18 Landing Stages

Three no. floating landing stages forsmall craft were installed under the jettycontract. Each landing stage comprisesof an articulated assembly of 2no.galvanised steel frames, each with 3glass reinforced (GRC) floats which arefilled with expanded polystyrene. Thefloating stages are located in position onplan by 2no. or 4 no. vertical piles406mm in diameter which guide thelanding stages vertical movement withthe change of tide.

The design of the landing stages iscomplicated by the large tidal variationfound on the west coast of Ireland where

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the range at spring tides is nearly 6metres. To maintain safe access for theusers of the landing stage it wasnecessary to incorporate an articulatedgangway of 17 metres in length, fixed tothe foreshore at one end and resting onthe landing stage at the other, to limit the

gradient of the gangway at low water.

5.19 Other Ancillary Works

In addition to the items alreadymentioned, further ancillary works werecarried out in the vicinity of the WestJetty. 3 no. access roads to the WestJetty were constructed. The east andcentral approaches are constructed of200mm concrete slab, while the westapproach is asphalt. The West Jetty hasnumerous items of steelwork furniturecomprising of safety ladders, traffic safety

barriers, low level safety kerbs and trafficsigns. The works also includedrefurbishment of an existing stone wallalong the harbour road for the full lengthof the phase 2 jetty extension.

6 Dredging Works

In parallel with the construction ofthe new West Jetty, the importantelement of development within the porthas been the improvements made to thebathymetric profile of the inner harbourarea and approaches through the recentdredging programme. Under thisdredging programme, approximately390,000 cubic metres of material wasdredged from the harbour.

6.1 Tendering for Dredging

In a process similar to the jettycontract, and under the EU directives forco-ordination of procurement procedures,invitations for pre-qualification werepublished in OJEC in January 1999 andten responses were received.

Tender documents for the dredgingproject were issued to seven tendererson 5

thJuly 1999 and were returned on

23rd

August 1999.Following a review of tenders,

discussions took place with the lowesttenderer, Irish Dredging Company Ltd,and a contract was later awarded on 12

th

November 1999.

The determination of dredgingquantities for both tender and contractmanagement was primarily carried outusing Hypack and Microstation software

packages.

Figure 15

6.2 Dumping Permit

Under the Dumping at Sea Act 1996,a dumping permit is required from theDepartment of the Marine and NaturalResources prior to dumping of anymaterial into the sea off the Irishcoastline. Among the details shown onthis permit are the quantity of material tobe dumped, the material composition, thedump location, and details of vessels tobe used.

Application was made in April 1999to the Department of the Marine andNatural Resources for permit to dumpdredge spoil at two specific locations,

with further updated information providedonce the contractor was appointed.

As part of the consultation processprior to issue of permit, the Department ofthe Marine and Natural Resourcesconsults with the Natural Monuments andHistoric Properties Service of DUCHAS(The Heritage Service). The servicesMaritime Archaeological Unit has statedthat all proposed dredging and dumpingsites must undergo archaeologicalassessment. Initially, a geophysicalsurvey of the relevant areas was carriedout using a side scan sonar and

magnetometer. Field records wereanalysed and the geophysical datareceived. Areas of anomalies were noted,and these specific locations were furthersite checked by diver using anexperienced marine archaeologycompany with diving experience. In all,seven locations identified by DUCHASwere examined. No artefacts, features ordeposits of archaeological interest wereobserved, but each location was verified.

A detailed report was issued to theMaritime Archaeological unit of DUCHAS.During the course of the dredging works,archaeologists carried out monitoring ofthe dredged material to confirm the pre-contract findings.

As part of the investigation of the

dumpsites, a photographic record andreport of the immediate foreshoreopposite the sites was carried out. Ashoreline survey examined the site offormer fish wiers on the shore andverified that the disposal of materialwould not have a deleterious effect onthe shoreline. After due consultation withvarious third parties by the Department ofthe Marine and Natural Resources, apermit to dump spoil was issued inNovember 1999.

As the permit expired at the year-end, a new application for permit into theyear 2000 was sought and granted. The

permit was duly amended to expire on29

thFebruary 2000. Dredging after this

date was not allowed due to themovement of specified fish species withinthe Estuary. The species are listed underannex II of the EU Habitats Directive andare also designated a Red Data Bookspecies for Ireland. These speciesmigrate from the sea to fresh water tobreed during the period March to June.Whilst this cut-off was very onerous interms of delivery of the completedcontract, the contractor made every effortto ensure that the dredging element was

completed satisfactorily within thetimeframe.

6.3 Foreshore Licence

Application was made in April 1999to the Department of the Marine andNatural Resources for a ForeshoreLicence for the dredging works under theForeshore Act 1933. After due review ofthe application and issue of appropriatenotices to interested parties such asShannon Estuary Port, TheCommissioners of Irish Lights, MarineSurvey Office of the Department of theMarine and Natural Resources, and the

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Figure 16

British Admiralty Hydrographer, aForeshore Licence was issued inNovember 1999.

6.4 Maintenance Dredging

An ongoing sediment transportregime at Foynes requires that the innerharbour areas be dredged at regular

intervals to restore the depth of water toallow safe vessel movements into andaround the port area. This dredgingprocess is usually required on an annualbasis.

An amount approximating to 100,000cubic metres of material was dredgedfrom the harbour under maintenancedredging. This is comprised entirely ofsilt material.

6.5 Capital Dredging

In parallel with the construction ofthe West Jetty, it was necessary to makeimprovements to the bathymetric profileof the channel approaches and innerharbour area. The berths on the WestJetty and East Jetty were originallymaintained with a bed level of 10.15mOD and 11.3m OD respectively. Inorder to accommodate the vessels nowbeing used in the port, it was necessaryto deepen the berths on both jetties to 12.0m OD. This level is required to allowthe largest vessels to remain afloat in theberths at all stages of the tide.

In addition to dredging of the berths,it was required that all areas designated

for vessel movement in the port area bedredged to remove all material above alevel of 8.1m OD. This level is required

to allow the largest vessels to enter andleave the berthing areas during high tideand to ensure safe turning manoeuvres.Following the results of the navigationstudy carried out by H R Wallingford, itwas determined that an outcrop of rockencroaching on the shipping channelfrom the Foynes Island side should bepartially removed and reduced to the

design level of 8.1m OD.Approximately 390,000 cubic metresof material was dredged from the harbourunder capital works dredging. Thiscomprised of 330,000 cubic metres wassilt, 40,000 cubic metres of boulder clay,and 20,000 cubic metres of rock.

6.6 Dump Areas

There are two dump areasassociated with the dredging works. Theprimary dumpsite is located in the middleof the Shannon Estuary under thejurisdiction of Shannon Estuary Portsapproximately 2 km downstream ofFoynes Port and is 800 metres x 250metres in size, with an average depth ofwater of 36 metres below datum. Thisdump area is used for the deposition ofdredged silt and clay material.

The secondary dump area is locatedjust offshore of the southern bank of theShannon Estuary within Foynes Portjurisdiction, and is 100 metres x 75metres in size, with an average depth ofwater of 8 metres below datum. Thisdump area is used for the deposition of

dredged rock. It is envisaged that thisrock can be reused in its present position

for a future port-related developmentwithin the jurisdiction.

6.7 Silt Dredging

The majority of the silt material wasdredged using a trailer suction hopperdredger, the WD Medway II. This is atype of vessel that is designed

specifically for the task of removing softto firm overburden from the riverbed.This vessel is 19 metres in width and hasthe ability to load a hopper containedwithin its structure, of 3,700 cubic metrecapacity, by means of a centrifugal pumpattached to an articulated arm whilst thevessel is moving ahead.

At the bottom of the articulated armis a drag-head that, on this vessel, isequipped with a jet system to loosen firmmaterial from the river bed for removal bythe pumps. This vessel has a powerfulbow thruster that provides a high degreeof manoeuvrability. Unloading is bymeans of a bottom-dischargearrangement over the designateddumping area in deep water.

During the works, the trailer suctiondredger rate-of-dredge was of the orderof 15000 cubic metres per day over a 24-hour work period. The dredger is fittedwith a DGPS system for accuratepositioning at all times.

6.8 Dredging with a HydraulicBackhoe Dredger

The backhoe dredger Koura II was

used to dredge hard boulder clay materialand loose rock as well as areas of silt not

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Figure 17sufficiently to allow excavation by thebackhoe dredger. This operation wascarried out independently of otherdredging operations using a specialisedpontoon with 3no. on-board drilling rigs.Before the pontoon could locate over thearea, the rock above low water level wasremoved in the traditional manner using atrack mounted drilling rig.

3 The rock was drilled out with innerdrill rods to the required depth.

4 The holes were charged with up to130 kg of Frangex explosive.

5 The outer casing was lifted to

retrieve the initiating line.

6 The hole was stemmed to confinethe blast.

7 The drill rig was moved and theprocess repeated until sufficientcharges were placed for efficientdetonation of the explosives. Adetonator delay of 20ms was usedbetween blasts.

Using the pontoon at Barneen Point,a total of 755 holes were probed with the

outer casing, of which 352 weresubsequently drilled and blasted. A totalnumber of 67 blasts were carried outusing 4641 kg of explosive over a periodof approximately 17 days. Using the landbased equipment, a total of 7 blasts werecarried out using 596 kg of explosive.removed by the WD Medway II trailer

suction dredger. The Koura II is adedicated marine dredger consisting of aheavy duty hydraulic base machine withan extended boom, dipper and bucketarrangement, all on a rotating base fixedto a floating pontoon. The pontoon isfitted with a number of spuds, which arehydraulically operated legs that may beraised and lowered to allow the pontoonto sit with positive bearing on overburdenwhile dredging. The backhoe has aworking reach in excess of 12 metres.

7 Cost Summary

A summary of the costs arising onthe project is as follows:

Preliminary investigation IR 150,000Jetty Works IR 7,100,000The outline procedure for blasting of

rock was as follows: Dredging Works IR 2,000,000Navigation Studies IR 100,000Charges IR 350,000

IR 9,700,000

When the material is excavated withthe backhoe, it is then loaded into abarge for dumping. In this contract, thebarge was a split hopper barge called theM.V.A.. Unloading of the M.V.A., like theWD Medway II, is by means of a bottom-discharge arrangement over adesignated dumping area in deep water.The working capacity of the backhoe is600 cubic metres per 4 hours necessary

to fill the bottom dump barge.

1 A drilling pattern was set up on a 2.5metre by 3 metre grid.

2 At each location, the outer casingwas lowered to the riverbed, throughany soft material and collared intothe rock.

All works were instructed followingcompetitive tendering in compliance withEU procedures. Throughout the works,cost control was monitored by the DesignTeam and cost reviews made on amonthly basis.

6.9 Rock Dredging

Approximately 20,000 cubic metres ofrock was dredged from the harbour. Thebulk of this material was located atBarneen Point on Foynes Island. Frompre-contract investigation, the UCS of therock was determined to be of the order of75 MN per Sq metre. The rock wasresistant to removal by backhoe andrequired pre-treatment before it could beexcavated.

The pre-treatment consisted ofdrilling and blasting, to fracture the rock Figure 18

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8 Project Quantities

The leading quantities on the capital works are asfollows:

Piling1067 diameter 5,701 Lin m

356x406 UC 1,184 Lin m350x350 concrete 1,288 Lin m

Reinforced ConcreteInsitu concrete 6,953 Cu mPre-stressed concrete slabs 2,454 Sq mPre-stressed TY7 beams 2,074 Lin m

ReinforcementInsitu concrete 1,122 tonne

Crushed Stone Filling 18,704 Cu m

Asphalt Surfacing 11,603 Sq m

DredgingSilt 330,000 Cu mClay 40,000 Cu mRock 20,000 Cu m

9 Acknowledgements

The authors would like to thank the Board of Foynes PortCompany for permission to present this paper, and themembers of the Design Team and the Contractors and Sub-Contractors for their assistance.

EmployerFoynes Port Company

Design TeamConsulting Engineers and Project ManagersMichael Punch & Partners

Marine ConsultantsHR Wallingford Ltd

Quantity SurveyorsHealy Kelly & Partners

Hydrographic SurveyorsHydrographic Surveys Ltd

Resident EngineersMr Peter BradleyMr Donald Cronin

Contractors for West JettyMain Civil ContractorsAscon Limited

Precast Concrete SuppliersBanagher Concrete

Steelwork SuppliersFoynes Engineering

Ground InvestigationsI.G.S.L.

Electrical ContractorPat Lane

Resident Engineers for DredgingMr Colin JohnstonMs Clare McCarthy

Contractor for DredgingMain Dredging Contractors

Irish Dredging Company Limited

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punch techpaper foynes port west jetty (1)

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