tp-growth and development of geotextile containers

8/12/2019 TP-Growth and Development of Geotextile Containers

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Case Studies Showing the Growth and Development ofGeotextile Sand ContainersAn Australian Perspective

Mr S.J. Restall Mr L.A. Jackson

Soil Filters Australia Pty Ltd International Coastal ManagementP O Box 727 P O Box 7196 G.C.M.C.Southport, Queensland, 4215 Gold Coast 9726Ph: +61 7 5539 3600 Ph: +61 7 5564 0564Fax: +61 7 4439 4027 Fax: +61 7 5532 9147e-mail: [email protected] e-mail:[email protected] Ing. Georg Heerten Mr W.P. Hornsey*Naue Fasertechnik GmbH & Co Soil Filters Australia Pty LtdWartmuntsr. 1 D-32312 P O Box 727Luebbecke Germany Southport, Queensland, 4215

Ph: +49 57 4140 0810 Ph: +61 7 5539 3600Fax: +49 57 4140 0883 Fax: +61 7 4439 4027e-mail: [email protected] e-mail:[email protected]

ABSTRACT

Soil Filters Australia Pty Ltd has been involved in the manufacture andinstallation of geotextile containers in a variety of forms since early 1984, thisrelates to 17 years experience in the field.

This paper outlines the historical development of the types of materialsused for geotextile containers and the diversity of applications in which these

containers are being used. The type of geotextile used for the containers variesdepending on installation conditions. This information has been compiled fromyears of experience. The range of application for these products is extensive andcovers areas such as scour protection, groynes, berms, artificial reefs andcontainment of hazardous materials.

The development of this form of coastal protection, has developed to sucha stage that in many cases it is no longer regarded as an alternative constructionmethod but rather the desired solution. This is not to say that there is not a greatdeal still to be learnt from this type of protection

Initially the main emphasis was on hydraulically filled geotextile tubes(typically 1.2m) used mainly as groynes to protect beaches. With time this

focus has changed to individual containers used in coastline protection andmarine structures (reefs).

Key Words: Geotextile, Containers, Tubes, Coastal, Australia
mailto:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]


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1 INTRODUCTION

A significant number of structures in the Australasian region have beenconstructed using sand contained in geotextile forms over the last 20 years. Thepractical experience has resulted in an evolution of the state of the art with

improved materials, design methods and construction methods. With theincreasing number of diverse community groups involved in the process ofconsultation, planning and approval, in some cases geotextile structures areproviding solutions to coastal protection and improvement where traditionalmaterials and their impacts and costs have not been acceptable to thecommunity and approval authorities.

A range of coastal protection projects using sand filled geotextilestructures have been constructed in Australia at sites from estuarine to opencoast since 1985. Numerous identified sites are as listed below:

Green Island

Gold Coast Broadwater North Kirra Groyne

Russell Heads

Lake Victoria

Maroochydore River and Beach

Kinka Beach

Great Keppel Island

Hamilton Island

Troubridge Island

Airlie Island

Towra Point Belongil Spit

Stockton Beach Motueka N.Z Waihi N.Z. Narrowneck Reef Maroochydore Groyne

Selected benchmark projects have been evaluated and show the progression tothe present state of the art.


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2 BENCHMARK PROJECTS

2.1 North Kir ra Groyne

Fig. 1. North Kirra Groyne

2.1.1 Project location

North Kirra, Gold Coast, Queensland

2.1.2 Date constructed

September 1985

2.1.3 Principal

Gold Coast City Council

2.1.4 Description

120m long x 5m high sand-filled groyne

2.1.5 Cost

~Aus$350,000 (cost of the rock alternative was estimated at Aus$600,000)

2.1.6 Project objectives


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A temporary structure was needed to retain nourishment to restore the erodedbeach, whilst long-term nourishment solutions were resolved to restore the longeroded southern Gold Coast beaches. The eroded conditions of these beacheshad long been associated with the economic down turn of the immediate area

due to poor tourism figures.

2.1.7 Site conditions

Easterly facing open surf beach with an offshore max wave height of >12m.

2.1.8 Community requirements and constraints

As the site is a popular surfing area and site of the local surf life saving club,thereforethe structure had to be safe for swimmers and surfers. It also neededto be removable if necessary after a permanent solution was implemented.

2.1.9 Construction techniques

The sand filled geotextile groyne was constructed of 100m long tubesencapsulated in geotextile envelopes (Figure 2). To minimise risk duringconstruction, and to allow for erosion of the seabed after construction, the groynewas constructed in a de-watered excavation following initial beach nourishment.This construction technique required an all weather, around the clock program,utilising a six-inch suction dredge pumping a series of one-metre diameter non-woven geotextile tubes that in turn were completely encapsulated in geotextileenvelopes. In order to minimise the time spent on site sewing geotextilestogether to form the seeled envelopes, the encapsulating geotextile was suppliedpre-manufactured 115m long by 20m wide (5 standard roll widths) dispensedfrom a hydraulically driven mandrill.

12.0 m

RL -1.5m

Terrafix 1200REncapsulating Envelope

1.2m dia. Sand filled Geotextile Tubes

Void between tubesfilled with dredged material

Fig. 2. Groyne X-Section


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2.1.10 Geosynthetics used

Heavy duty UV stabilised non-woven staple fibre needle punched geotextile(Terrafix 1200R) with high tenacity polyester thread in all seams.

Table 1Geotextile Tube & Geotextile Envelope Characteristics

Thickness CBR BurstTensilestrength

SeamStrength

5.5mm 10 kN @ 60%65kN/m XD38kN/m MD

Min. 80% ofbase fabric

2.1.11 Evaluation and comments

The project was ambitious in regards to the size of the structure and location in

an active surf zone. Conventional armour units were not an acceptable optiondue to the cost and difficulty associated with the ultimate removal of rock orconcrete. This groyne was a success in terms of achieving its primary objectiveof a safe temporary structure for beach stabilisation despite damage to theseaward end due to vandalism. The groyne length was reduced by about 20m,due to vandalism, before it was completely covered by a regional nourishmentscheme commenced in 1990.

Experience with vandalism lead to trials of coatings such as bitumen andearly patching techniques. As damage to a single long tube can have asignificant effect on the integrity of the structure there has been a trend awayfrom long tubes to smaller containers in order to isolate / mitigate damage.

Tubes still have an application where sufficient protection can be provided andthe techniques developed at North Kirra have been utilised on other tubeprojects.


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2.2 Russell Heads

Fig. 3.Aerial view of Russell Heads

2.2.1 Project Location

Russell Heads (Woolamaroo South), North Queensland. Boundered by MutcheroInlet River mouth at Constantine Point.

2.2.2 Date Constructed

1993 onwards

2.2.3 Principal

Local community

2.2.4 Description

250m long sand filled geotextile berms


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2.2.5 Cost

Not Available

2.2.6 Project ObjectivesCommunity based program to construct hydraulically filled tubes progressively asa beach stabilisation structure.

2.2.7 Site Conditions

Russell Heads is a fragile residential peninsula that has endured sixty years ofrecorded erosion influenced by a dynamic river system and seasonal cyclones.

2.2.8 Community Requirements and Constraints

The comparatively remote location limited resources and lack of governmentfunding presented a serious dilemma for the small Russell Heads community.What was needed was a solution which would allow the community themselvesto construct the protection works and with very little expensive/specialist plantrequirements.

2.2.9 Construction Techniques

By combining their resources, the community constructed a small dredgeenabling them to install hydraulically 1.2m dia. sand filled geotextile tubes andnourish the beach in a series of progressive working bees. This program hascontinued for a number of years.


Heavy duty UV stabilised non-woven staple fibre needle punched geotextile withhigh tenacity polyester thread in all seams.

Table 2Geotextile Tube Characteristics


SeamStrength

5.5mm 10 kN @ 60%65kN/m XD38kN/m MD


2.2.11 Evaluation and Comment

The results of the residents actions have been positive. Several houses weresaved as a result of these works during cyclone Justin in 1997.


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Although the wave climate was such that displacement of the tubesoccurred, the inherent flexibility of the no woven needle punched material utilisedenabled re-alignment and settlement to follow scour contours and continue toprovide stabilising protection.

2.3 Maroochy River Groynes

Fig. 4. Maroochy River Groynes


Maroochy River, Maroochydore, Queensland


1994

2.3.3 Principal

Maroochy Shire Council

2.3.4 Description

50m long x 4m high sand-filled groyne


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2.3.5 Cost

Aus$219,000


To put in place appropriate mechanisms to impede the increasing erosion andriver alignment. (Full details of the investigation are covered in the paper byCoughlan and Mootoo 1995).

2.3.7 Site Conditions

The southern bank of the Maroochy River is a popular tourist destination frontinga large Council operated Caravan Park, which has suffered severe erosion sincethe 1980s.


To ensure the nourishment and stabilisation process provided a user-friendlyamenity without spoiling the natural beauty and popularity.


Two substantial groynes were constructed utilising sand filled geotextile tubes.Each groyne was fifty metres long and the design incorporated an extensivefoundation layer to counter potential scour as indicated in the physical modelling.

The constructed height of over 4.0 metres utilising a multiple stack of 1.2metre diameter tubes, incorporated a 30kN/m geogrid in the foundation layersand first layer, fully encapsulating the respective layer to prevent the possibility oflateral displacement (Figure 5).

1.2m dia. Geotextile Tubes

Geogrid100mm Grout injected mattress

Fig. 5. Section through groyne structure


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The tubes were manufactured from polyester staple fibre needle punchedgeotextile, and were filled by Council day labour work crews in conjunction withplanned sand nourishment. Having learnt from the Kirra project where vandalismcompromised the integrity of the groyne as a long term solution theCouncil optedto encapsulate the two groyne structures in a grout injected mattress for

additional resistance to vandalism and pedestrian traffic.


Heavy duty UV stabilised non-woven staple fibre needle punched geotextiletubes with high tenacity polyester thread in all seams. Tenax LBO301 Bi-oriented polypropylene geogrid and Fabri-form polyester woven multifilamentgrout injected mattress

Table 3Geotextile Tube Characteristics

Thickness CBR BurstTensile

strength

Seam

Strength5.5mm 10 kN @ 60%

65kN/m XD38kN/m MD


Table 4Geogrid Characteristics

ApertureTensilestrength

Elongation

40mm x 30mm31kN/m XD19kN/m MD

11%16%

Table 5Mattress Characteristics


SeamStrength

No information available


Six years after installation, the groyne structures are performing in accordancewith the design expectations, and the amenity of the area is vastly improved.

Wide beach widths are now the norm with no nourishment taking place. Thegrout-injected mattress used to protect structure has prevented vandalismhowever the fabric portion of the mattress has deteriorated substantially exposingsharp grout edges and this could pose some health and safety risks topedestrians. This type of rigid cover/facing is not suited to a flexible geotextilestructures, hence the investigation into flexible hardwearing cover layers, such asimpregnated and composite fabrics which when combined provide strength,elongation and high wearing and puncture resistance.


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2.4 Stockton Beach Revetment

Fig. 6. Stockton Beach December 2000


Stockton Beach is located to the north of the Hunter River trained entrance inNewcastle.


1996

2.4.3 Principal

Newcastle City Council

2.4.4 Description

48m long by 4.5m high double layer sand container revetment, at a 1.5H:1Vslope.


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2.4.5 Cost

Aus$24,000 (materials only)


To provide temporary erosion protection to the Surf club. Severe erosion to thebeachfront at Stockton beach had placed the Stockton Beach Surf LifesavingClub in danger of collapse. Due to state government regulatory requirements aninterim measure was the only rapid solution whilst a coastal management planwas finalised.


Exposed ocean beach with wave heights of greater than 5m.


A user-friendly aesthetically pleasing structure.


The empty geotextile containers are placed in a filling frame and filled using anexcavator, the container is then sewn closed using a hand held sewing machine.The containers are then lifted and placed using a modified rock grab, the rockgrab is modified in such a way as to limit the stress on the geotextile during thelifting operation.

The containers when full were 1.5m x 1.1m x 0.4m and were laid in astretcher bond format to ensure maximum interlock at a 1.5H:1V slope. A self-healing Dutch Toe was incorporated into the design to prevent scouring of thetoe of the wall during large storm events. The figure 7 shows the as built doubleskin container layout and the self-healing toe detail.


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2.4.11 Evaluation and comment

This was the first of the engineered sandbag revetments constructed to protectoceanfront properties. The option to construct in this manner was largelyinfluenced by the immediate need for protection of the site. The revetment was

built as a temporary/removable structure, as approvals for a permanent structurewould not have been issued without a full environmental assessment, into theimpact of the long term/permanent proposal. Time taken to prepare thedocumentation and receive approvals for a permanent solution, i.e. the moreconventional rock wall approach, would have delayed the project for somemonths and would undoubtable have lead the loss of the valuable surf lifesavingclub buildings. The loss of the structure was unacceptable to both the NewcastleCity Council (owners of the property) and the general public.

Despite the temporary nature of the structure, the non-woven geotextilecontainers have withstood a number of storm cycles over five years of service.This installation has outlived the original design requirements and met the

objectives of protecting the surf club whilst complying with providing a softinterim solution to the total coastal management problem at this site. The softsolution has also proven popular with beach goers who find the structure a userfriendly option when compared with conventional rock and concrete structures.To date no permanent works have been carried out and further extensiveworks, using Sand Containers, have been proposed for the properties adjacent tothe site with construction due to begin in late 2002.

The success of this revetment has lead to a number of other areas suchas Belongil Spit at Byron Bay, Airlie Is in W.A, Troubridge Is in S.A. utilisingsimilar site appropriate techniques. The colour of the geotextile was important tosome clients who wanted the structure to blend in with the natural surroundingsto make the structure as unobtrusive as possible. The advantage on thenonwoven geotextile in regard to this requirement is that the open structure trapsthe local soil / sand and therefore takes on the colour of the surrounding area.


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2.5 Narrowneck Reef

Fig. 8. Narrowneck Artificial Reef Aerial View


A narrow isthmus between Surfers Paradise and Main Beach, Gold Coast,Queensland


1999-2001

2.5.3 Principal

Gold Coast City Council

2.5.4 Description

400m x 200m Submerged reef

2.5.5 Cost

Aus$2.5M (The cost of rock was estimated at ~$5M)



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Easterly facing open surf beach with an offshore max design wave height of>12m.


The reef is an integral part of the Northern Gold Coast Beach Protection Strategywhose aim was to widen and protect the northern beaches as well as enhancingthe surfing amenity. The reef would provide a low profile, near shore control pointto retain approximately 80,000m3 of the 500,000m3 of sand transported eachyear to the north along this shoreline.


The public supported a user-friendly structure, the stakeholders identified at timeof design was the surfing community however now that the reef has matured thefishing community is also making use of the facility. A condition of approval was

for modification and even total removal if required. The mega sand containersfacilitated these requirements.


Nearly 400 mega sand containers varying from 3.0 metres to 4.6 metres indiameter, were placed using a split hulled, trailing suction hopper dredge fittedwith computer interfaced DGPS. The containers were accurately filled utilising acalibrated density metre, ensuring repeatability and consistency of theconstruction. Containers were dropped in depths of water ranging from 3m to11m, onto a sandy seabed.


3 4.5m x 20m (max 400tonne) Soft Rock Mega Containers manufacturedfrom heavy-duty polyesterno woven geotextile (Terrafix 1200R).

Table 8Geotextile Container Characteristics


SeamStrength

5.3mm 10 kN @ 60%65kN/m XD

38kN/m MD

Min. 80% of

base fabric


The ability to fill to a pre-determined shape and accurately place very largegeotextile containers at a very low unit cost was conclusively proven. Duringconstruction total supplier and installer alike revised methodology, these


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improvements were implemented to ensure the durability and longevity of thestructure.

Initially some failures occurred, during filling and release of the containers,along the seams. With improvements to the calibration of the dredge feed andcontainer shape these types of failures were eliminated. Damage also occurred

to some containers during laying, generally due to contact with the dredge inshallow water. Very effective underwater patching techniques were developed torepair this damage. The holes are sealed with a silicone based adhesive and apatch is screwed down over the hole, using nylon wall screws, to provide addedprotection.

Various coatings were trialled for the crest bags with mixed success buttowards the end of the construction a durable composite (hybrid) material wasdeveloped and tested with great success. Initial trials made use on a spray onpolyurethane coating of various thicknesses, however this product became rigidonce exposed to water and in fact made the products more susceptible to impactand wave damage. The composite material, consisting of two layers of non

woven geotextile, used towards the end of the project allows entrapment ofapproximately 4kg/m2 of sand and shell particles within its structure, once thegeotextile is impregnated with these particles the puncture resistance of thegeotextile shows significant improvement.

The porus nature of the non woven geotextile makes it an ideal platformfor marine growth, within months the containers are covered with a thick growthof seaweed. This structure is now host to a large number of marine creatures andthe reef has now become a popular fishing spot. An investigation into theenvironmental impact of the reef on the marine life is underway at the moment.

Although some top up is still required, monitoring has shown a clearsalient at times and enhanced surfing conditions. Full details of the numericalmodeling for the design of the surfing wave break on the reef are covered in thepaper by Mead & Black; Design of the Gold Coast Reef for Surfing, Public

Amenity and Coastal Protection: Surfing Aspects (2001).As construction progressed positioning of the dredge and placement of the

Mega Containers became more difficult as the wave characteristics changedabove the existing containers. This reinforced the concept that filling in placewould be very difficult if not impossible, concluding that the method adopted wasboth effective and efficient.

2.6 Maroochydore Beach Revetment

2.6.1 Project Location

This beach is located at the dynamic mouth of the Maroochy River, Queenslandintersected by Pincushion Island.



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2000-2001

2.6.3 Principal

Maroochy Shire Council

2.6.4 Description

200m long by 2.5m high single layer sand container revetment, angle of repose75 deg.

2.6.5 Cost

Not Available


Interim protection measures to stabilise the foreshore.


The mouth, continuing a trend identified in the late 80s and early 90s, revertedto a more southerly discharge. During November 2000, the erosion problem onMaroochy Beach had propagated to such an extent that the foreshore andcaravan park were likely to be threatened during the imminent cyclonic seasonand king tides.


Utilising two small excavators, (5 tonne and 8 tonne), 3000 nonwoven geotextileunits were filled and placed as a defence barrier in the dunal system.


2t TerrafixSoft Rockgeotextile containers and UV stabilised non-woven staplefibre needle punched geotextile (Terrafix 600R)



SeamStrength

5.3mm 7.0 kN @ 60%42kN/m XD27kN/m MD



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Table 10Geotextile Characteristics

Thickness CBR BurstTensile

strength

5.0mm 5.4 kN @ 60%31kN/m XD

16kN/m MD


During the early months of 2001, king tides repeatedly tested the interim defencebarrier. Observations of direct overtopping during consistent 2m-wave attack,proved that the stability of such structures was higher than expected. Someundermining of the toe occurred during king tides and 3m swell in January 2002(Figure 9), which resulted in the settlement of approximately 35m of the wall.Such conditions would have resulted in a failure of a rubble wall with the same

design (2.5m high 1.1m thick @ 15deg. off vertical). Toe protection of thestructure was identified as a very important feature of any wall, correct depth ofbase and a self-healing toe (figure 7) will ensure the durability of the structure.

Fig. 9. King tides and 3m swell January 2002

The self-healing qualities of high elongation flexible Soft Rockcontainershave been proven. Some containers have been damaged but the integrity of thestructure has not been compromised, as the containers have been able to mouldthemselves into the void left by the damaged container (Figure. 10).


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Fig. 10. Self healing characteristics of Soft Rockwall

Although not the first application of its kind the success of the project(withstanding severe storm attack) has lead to the construction of a groyne aspart of the works using innovative products and construction techniques.


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2.7 Maroochydore Beach Groyne

Fig. 11. Maroochydore Groyne November 2001


Maroochydore Main Beach, Sunshine Coast, Queensland


November 2001

2.7.3 Principal

Maroochy shire Council

2.7.4 Description

100m long x 2.5m high sand-filled groyne

2.7.5 Cost

Aus$210,000



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To stabilise the Maroochydore main beach which had eroded by approximately75m within 2 years. The structure had to be easily removable should it bedetrimental to the beaches north of the groyne.


Easterly facing open surf beach with an offshore max wave height of >10m.


As the existing Soft Rock revetment wall was proving to be popular withfishermen and the general public a similar structure was envisioned. Thisstructure would blend in with the natural sandy beach and would not form ahazard to beach goers.


The groyne consisted of 4 layers of containers stacked into a pyramid shape asshow in Figure 12. An 8t excavator was used to fill the containers while a 35texcavator was used to place the containers.

2500 mm

5223PR Soft Rock Containers

Fig. 12. Section through groyne


4.5t Terrafix Soft Rock geotextile containers manufactured from a compositeUV stabilised non-woven staple fibre needle punched geotextile (Terrafix

1209RP) with high tenacity polyester thread in all seams.



SeamStrength

11mm 12kN @ 60%75kN/m XD45kN/m MD



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2.7.11 Evaluation and comments

The geotextile sand containers and construction methods used in this project area result of the years of development into geosynthetic containers described asdescribed in the previous case studies.

For an exposed structure of this nature it was felt that the 2t containersused on the revetment wall were to small and that the container size would haveto be increased substantially to ensure stability. The weight/size of the containerswere limited however to the capabilities of a 35t excavator as this type ofexcavator is accessible to most contractors. The containers were be installedusing specially developed filling and placing apparatus designed to ensureimproved filling and simple handling of such large containers. The method oflifting and placing containers with a modified rock grab, as with the 2t containers,would have over stressed the geotextile and seams. The containers are filled inthe lifting/placement cradle and placed using the 35t excavator, no doublehandling of the container is necessary. This method of placement is thought to be

the first of its kind in the world, which allows very accurate positioning with lowstress on the geotextile and seams (Figure 13).

Fig. 13. Placement using specialised equipment

The composite geotextile developed for the Narrowneck reef project wasused for all containers in the groyne minimising risk due to vandalism. After7months of use only one incident of vandalism has occurred and was patchedusing the screw down patch method described in the Narrowneck case study.Specialised sewing equipment was developed for this project to ensure a high


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strength seam on this thick puncture resistant geotextile (Narrowneck containershave a different seam detail).

The groyne has performed exceptionally well and has withstood waveheights of greater than the 3m design height, the council is now investigating theconstruction of a further groyne based on this performance.

3 CONCLUSION

The use of geosynthetic containers in marine structures is a relatively newscience, however a great deal has been learnt from both the successes andfailures of these structures and the scope / limits of their application are yet to bedefined. The development of this field is unique in that it has relied on the closecollaboration between clients/consultants, contractors and manufactures toprovide the best solution.

Sand filled geotextile containers are a relatively new field of application forgeotextiles and with this new application comes new requirements for durability

and survivability. This poses the question: Are our current test methods adequateto ensure effective specification of geotextiles? Being exposed to the elementsby a far higher degree than most other geotextile applications e.g. drainage andseparation, damage to geotextile sand containers used in marine structures,whether it be by accident or vandalism is a serious threat to the durability andlongevity of these structures. There are very few tests available which a designercan use to asses and compare the suitability of the various geotextiles used inmarine applications, this means that the designer must rely on past experiencewhich is likely to be limited or gut feel which is undesirable.

- Vandalism has been identified by a number of clients as the mode ofdamage, which is of most concern. At present there are no indicator testsavailable, that model puncturing of the bags using a sharp instrument,hence there is very little information available to the engineer on which tobase the vandal resistance of the various geotextile. One solution may beto modify the current ASTM D4833-00 puncture resistance test to from aknife-edge thereby mimicking a knife cut by a vandal.- Abrasion of geotextile containers is another area of concern particularlyin areas where coarse angular sand or coral debris is present and herethe German Baudesanstalt fur Wasserbau rotating drum test method isrecommended, as this test best replicates the abrasive near shore surfenvironment.The development of improved seaming methods is allowing larger

containers to be constructed, which can be subjected to higher stresses.Improvements in seaming, filling, handling and placement techniques haveimproved the quality of structures built and have also increased the diversity ofuses. Damage whether it be accidental or premeditated has prompteddevelopment of hybrid geotextiles (used in the Narrowneck reef & Maroochydoregroyne projects) designed specifically for hostile marine conditions.

Containers can be manufactured to suit not only the physical applicationbut also to the equipment available to the contractor, hence their use is suited to


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specialist installers who have access to split hulled barges (Narrowneck reef) andto smaller contractors with limited resources (Russsel heads communityconstruction).

To summarise the views of Soil Filters Australia:

Geotextiles structures can be successfully used to solve conventionalcoastal problems and non-conventional challenges.

Nonwoven sand filled geotextile structures adapt and conform readily tochanging site conditions.

Design and construction approach requires specific consideration of site-specific conditions and geosynthetic techniques. Factors such as vandalismpotential, abrasion potential of the beach sand, interface friction in a multilayer structure etc must be addressed in any design.

Durability is often higher than anticipated and continues to improve withadvances in Geotextile manufacturing techniques, related polymer science,and container manufacturing methods.

Sand filled geotextile forms can create an excellent foundation for a broaddiversity of marine species.

In the event that something goes wrong in the complex field of sandy beachsystems, the geotextile sand containers can be easily removed compared toother structures.

In general there is a lack of specific test methods, which can be used tospecify geotextiles in marine applications.

Geotextile structures are user-friendly features ideal for recreationalfacilities such as beaches.

REFERENCES

German Federal Waterways Engineering & Research Institute, (1994).

Guidelines for testing of geotextiles in hydraulic engineering applications.

Heerten, Dr Ing. et al (2000). New Geotextile Developments with Mechanicallybonded Non Woven Sand Containers as Soft Coastal Structures. 27thInternational Conference on Coastal Engineering, Sydney, Australia, 16 21 July2000, pp. 2342- 2355.


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Jackson, L.A., (1987). Evaluation of Sand Filled Geotextile Groynes Constructedon the Gold Coast. Internal Report for Gold Coast City Council.

Mead, S., Black, K., (2001). Design of the Gold Coast Reef for Surfing PublicAmenity and Coastal Protection: Surfing Aspects. Journal of Coastal Research

No 19, The Coastal Education and Research Foundation (CERF), pp. 115-130

Mootoo, T., Coughlan, P. (1995), Sand Filled Geotextile Groynes as BankErosion Protection within the Maroochy River Estuary, Sunshine Coast,Queensland.

Pilarczyk, K.W., (2000). Geosynthetics and Geosystems in Hydraulic and coastalEngineering. A.A. Balkema, Rotterdam, the Netherlands, 2000.

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