GEOSYNTHETIC CLAY LINERS
Why GCL’s are preferred ...
Introduction
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Who is the “GCL Alliance”? As Geosynthetic Clay Liners (GCL’s) demand expertise and technical understanding, two leading manufacturers have combined their resources to form “The GCL Alliance” – - Geofabrics Australasia Pty Ltd’s manufacturing operation (ELCO Solutions Pty Ltd) in Australia, has supplied millions of m² of GCL’s over the past decade throughout Australia, south-east Asia, New Zealand and other regions. We have worked closely with leading global designers on many large projects, including international projects with complex quality requirements and tight delivery programs. - Kaytech Engineered Fabrics in South Africa has over 40 years of geosynthetic experience, with nearly 15 years experience with GCL’s in southern Africa. Having supplied GCL’s to extremely complex waste management and mining projects, Kaytech has recently invested in a new state-of-the-art GCL manufacturing facility.
Combining our skills and experience allows us to work with you globally with our high level of support and energy.
Introduction
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What is a GCL? Geosynthetic Clay Liners (GCL’s) are a specialised geosynthetic product used as a sealing mechanism in containment structures. Essentially, GCL’s are a “clay sandwich”, where bentonite clay is placed and held between two layers of engineered geotextiles. With the right raw materials, a 10mm thick GCL can give the same sealing performance as a 1m thick compacted clay layer (CCL) – meaning more room inside your containment structure for your waste (and where room is money, such as in a landfill, this is a significant benefit). The prime function of a GCL is to seal the waste or liquid inside the containment structure (e.g. a landfill). Whilst other engineering attributes are important (e.g. shear resistance when placed on a slope) , the primary function of a GCL is to act as a sealing or waterproofing solution.
GCL’s are delivered in rolls, and follow an easy installation process. There is no need for complicated welding or measurement of compacted clay layers.
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Introduction
How are GCL’s made? GCL’s are typically made through technology that places bentonite clay onto a bottom layer of woven geotextile, with the top layer of non-woven geotextile then being placed. The two layers of geotextiles are then needle-punched together, meaning that the fibres from the top layer are dragged from the top to the bottom by needles. This process forms the “clay sandwich” and helps the structure resist separation when the clay gets wet and starts to swell. The finished product is then packaged as a roll, wrapped in a durable plastic wrapper and stored undercover until despatch. Obviously there is much more that we do to our GCL’s to make them the leading GCL’s in the world (such as using powdered sodium bentonite, thermal locking technology, advanced edge treatment, use of engineered geotextiles etc),
but in essence, this is how GCL’s are made.
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Introduction
How do GCL’s work? GCL’s work as a sealing or waterproofing solution through the bentonite clay reacting when in contact with liquids to form a hydraulic barrier. To obtain the best results from a GCL, one needs to understand what clay source and type is being used in the manufacturing process. We use powdered sodium bentonite clay particles with very tight QA/QC requirements. The use of high-end clay allows our GCL’s to provide a higher hydraulic barrier than other GCL’s. Understanding the clay within a GCL is the key to providing a world-class containment structure. The engineered geotextiles along the top and bottom provide the GCL with a stable structure. They also provide the basis for the mechanical performance (e.g. shear resistance, tensile strength, etc) that is also important in ensuring the GCL performs. Varying the inputs of clay and geotextiles allows different grades to be used. As a designer, contractor or asset-owner, it is important to understand these basic elements, for the consequences of not fully containing the waste or leachate are severe.
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Introduction
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GCL APPLICATIONS LANDFILLS & CONTAINMENT
GCL’s are widely used as a hydraulic barrier in landfills (along the base, up the slope and as a capping layer), generally as of an engineered containment system.
MINING
GCL’s are used as a lining system for tailings dams and residual disposal areas, as well as in mine remediation projects.
LAND REMEDIATION
GCL’s are used in land remediation projects, where contaminated land or waste requires encapsulation. Use of a GCL permits a simple installation process, allowing the project to continue without delay.
SECONDARY CONTAINMENT
GCL’s are used as part of the containment system around petro-chemical tank farms, as they help contain the liquid should a tank burst or fail.
BASEMENT WATERPROOFING
GCL’s are widely used as a waterproofing solution for basements, car-parks, home theatres, wine cellars etc. Placed against the concrete, the GCL helps waterproof the structure.
LANDSCAPING & WATER STORAGES
GCL’s are used to provide a lining system for golf course water features, ponds, farm dams etc. High-quality GCL’s significantly reduce the infiltration of water into surrounding soil (i.e. reducing the water loss through seepage). GCL’s are also used in Wastewater Treatment Lagoons.
TUNNELS
GCL’s have been used as part of the waterproofing system for tunnels around the world.
CANALS
GCL’s have been used in canal linings to reduce the infiltration into the surrounding soil.
(or hydro-carbon storage)
Applications
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Landfills and waste containment GCL’s are widely used in landfills as part of the liner system. The GCL can be used on the base, down the slopes and along the cap of the landfill. Understanding the forces on the liner system in the different areas within the landfill structure allows specification of the appropriate grade of GCL for each area. The parameters of the containment structure will determine the forces applied to the GCL, which needs to resist such forces. GCL’s using powdered sodium bentonite particles have an excellent sealing performance, with the system having a much lower permeability much earlier than other clay types.
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Applications
Mining Mine processes create waste that can be difficult to contain, including extreme pH or highly aggressive waste. The use of tailings dams, residue disposal areas or red mud dams commonly use compacted clay – but the lining of such structures requires careful thought. When confronted with a difficult mining application, we test the compatibility of our GCL with your specific leachate or waste, thereby ensuring the correct matching of products as part of your solution.
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Applications
Land Remediation GCL’s are commonly used to contain or cap contaminated land or in mine closure applications. Generally in these applications, rainfall or groundwater moves through the contaminated soil, thereby carrying chemical constituents that are best kept on site. As GCL’s provide an extremely low permeability barrier, there is nearly zero movement of liquid waste from the contaminated site to the surrounding environment, thereby assisting the designers in achieving their desired aim.
Applications
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Secondary containment (or hydro-carbon storage) GCL’s are used as part of the containment system around petro-chemical tank farms. containing the liquid should a tank burst or fail.
They assist in
Hydro-carbons are very difficult to contain when spilled, as they tend to enter the surrounding soil and groundwater very quickly. Generally such spills are cleaned up within days, hence the GCL is required to react quickly to minimize ingress of the liquid into the surrounding soil. We have done many projects with our GCL in secondary containment applications, and have worked with leading industry players to develop the right solution for their circumstances and hydro-carbons.
Ask us regarding our experience in using our GCL’s in this application, to ensure your structure is properly protected.
Applications
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Basement waterproofing GCL’s are widely used as a waterproofing solution for basements and other building applications. Placed against the concrete structure, our GCL’s help minimise the flow of groundwater from the surrounding soil through the concrete to the internal face of the basement (e.g. a car park, basement area, wine cellar etc).
We manufacture a completely different range of GCL solutions for basement waterproofing applications, as there are different issues to consider, such as handling, ease of placement, installation etc.
Should you have a specialist or different style of application, please contact us for advice on your project. Generally we will have worked on a similar project somewhere else.
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Applications
Landscaping and water storages As a sealing solution, GCL’s are ideal for water storages – especially structures which can utilise simple to install solutions. We have a rich history of using our GCL’s in water storages – including farm dams, wastewater treatment ponds etc. By using commonly available earth-moving equipment, GCL’s can be placed simply and quickly to form an effective hydraulic barrier. This then dramatically reduces the loss of water into the surrounding soil.
GCL’s allow children or animals who enter the water storage to easily exit as there is no slippery surface.
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Applications
Tunnels Our GCL’s have been used in tunnels as part of the waterproofing system. We recently provided ELCOSEAL® GCL’s to the Cebu tunnel in the Philippines to waterproof the tunnel system. The design and installation of the waterproofing system is a critical element of any tunnel, and the use of GCL’s in this application is growing due to their effectiveness in waterproofing as well as their ease of installation.
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Applications
Canals GCL’s have been used in canal situations in a variety of situations, including vertical cut-off trenches (to reduce seepage from the earth canal wall to the surrounding soil), under concrete lined channels (to prevent seepage through the concrete channel into the surrounding soil), as well as in major canal structures. GCL’s offer a simple solution to reduce the seepage in canal applications.
Benefits
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Benefits of a GCL Our GCL’s offer a number of advantages to installers, asset-owners and designers, including
Fast and efficient delivery of goods Extensive R&D conducted in sodium bentonite chemistry and GCL shear strength High internal shear for steep slopes for enhanced system performance Long term shear and swell stability High interface friction Ability to seal damaged areas No specialist joining technique required Simple deployment of product, supported by installation equipment and supervision Custom grades and roll lengths available Unmatched sealing capacity Extremely fast response time to hydration Avoids on-site mixing of bentonite powder Consistent hydraulic performance
We aim to be supplying all our projects on-time, in-full and to specifications. We resource ourselves to achieve this aim.
Benefits
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Benefits of a GCL These benefits translate into benefits for the installer, including Reducing costs through the ability to use his own construction team and equipment Providing more manageable lead times for supply of goods Reduced construction risk through increased confidence that all manufacturing QA/QC issues are addressed every time, on time Designing the product to suit the project (e.g. having a longer roll length allows the installer to have a roll for the full length of slope, rather than a join towards the toe of the slope – thereby reducing the risk of failure)
Use of powdered bentonite provides rapid hydration time, allowing a great ability to self-seal as well as sealing immediately after placement (i.e. for evidence of this, examine the quick water test showing the initial leakage rates through granular bentonite GCL’s)
Specialist treatment of overlaps ensures sealing performance along edges is first-class Support for installation is available to provide initial training and advice Reducing costs through using custom grades – i.e. more closely aligning the product’s characteristics with your project needs.
We have the knowledge, products and systems to reduce the risk and costs to the engineers designing or building the structure.
Benefits
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Benefits of a GCL over compacted clay layers (CCL’s) GCL’s offer a number of benefits when compared to CCL’s, including – Being a more consistent sealing system Being cheaper to install, through the initial cost of the components, but also being quicker and simpler to install (especially in areas where the clay is difficult to work with or where rain plays a role) Giving the structure more storage volume through a GCL being a thinner hydraulic barrier With reserves of good quality clay being more difficult to source, and the costs of the existing clay reserves increasing, the use of GCL’s as an alternative to CCL’s is increasing. GCL’s are a cheaper solution to CCL’s, but also permit greater storage volume within the structure – further enhancing the economic argument for GCL’s. Additionally, CCL’s by their very nature are highly variable as a containment system. There is always great variation amongst different clay sources, as well as the naturally inherent variation within an individual clay source. Variability further increases when working with specific wastes (e.g. caustic waste from mining processes).
The compaction and construction techniques then add another layer of variability to the structure.
Quality GCL’s are easier to work with than clay, as clay can be variable, difficult to compact, crack or desiccate, and delays construction after rain storms.
Benefits
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Benefits of a GCL over phyto-covers Phyto-covers are an emerging concept in lining systems. Essentially a phyto-cover tries to use the benefits of nature (i.e. soil and vegetation) to provide a hydraulic barrier. GCL’s offer a number of advantages over phyto-covers, including
GCL’s are easier and cheaper to install
GCL’s offer much increased void space, for phyto-covers can be 1-2 metres thick (which is important in landfills and other structures)
GCL’s are a proven technology, with proven long-term performance
GCL’s are much less susceptible to changes in climate and soil type (e.g. how well does a phyto-cover perform during a drought period or under tropical rain patterns?)
GCL’s offer a superior strain performance under high differential settlement.
Quality GCL’s are a proven technology, offering many benefits over phyto-covers.
Features
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Features of a GCL Our GCL’s have the following features We manufacture our GCL’s in world-class factories to international standards by geosynthetic specialists with extensive history with using GCL’s All aspects of our GCL’s are engineered for performance We fibre reinforce the bentonite powder through the needle-punching process, and then thermally-lock the reinforcing fibres to increase the performance of the GCL We use world-class clay sources, with strict QA/QC on the incoming raw material. As the clay provides the sealing characteristics, it is important for the designer to understand the clay used in the GCL. The use of powdered sodium bentonite clay particles brings many benefits to our GCL, including enhanced sealing characteristics Our GCL’s allow simple installation techniques to be used, and we support our GCL’s with specialised installation tools, manuals and other services Our GCL’s have enhanced performance in the overlap between adjacent rolls, reducing the risk of failure We have a flexible manufacturing process that offers significant savings for your project (e.g. through customer grades or roll dimensions)
We manufacture world-class GCL’s that can meet the most exacting performance criteria in the world or can be manufactured specifically to suit your project requirements.
Features
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Our GCL’s offer a number of technical benefits We only use powdered sodium bentonite particles – supported by extensive research to prove the high-quality performance characteristics of our clay We fibre reinforce our GCL’s, as well as thermally locking the fibres into place We only use polypropylene fibres in the non-woven geotextile (an important element in ensuring durability of the GCL over the long-term)
We use a controlled manufacturing process, with a rigorous, third-party endorsed manufacturing QA/QC regime We have developed specialised treatment for the edge details to ensure all risk of increased leakage through the overlaps is minimised We use our own full-time, on-site laboratories, supported by regular external third-party assessment by leading international GCL laboratories Our staff have decades of experience in the manufacture and use of GCL’s in many applications.
If you wish to know why these features are important to your project, please contact us and we will be very happy to explain the technical details of each part of the GCL and the environment within which it operates.
Installation & Delivery
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Delivery Our GCL’s are delivered to your site generally in one of two ways -
- for export projects – the GCL rolls are packed in a shipping container
- for projects in Australia and South Africa – the GCL rolls are delivered on the back of a truck In the past, we have assisted clients with the movement of GCL’s on their site through providing them with either a prong to move each roll individually or to place slings around each roll. How you handle the rolls needs consideration, for the safety of your team is important to all of us.
For example, if you elect to use slings or a prong to move the rolls around the site, please make sure the handling equipment is in first-class condition and correctly rated by the appropriate safety body.
Installation & Delivery
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Installation The installation of GCL’s comprises several elements, including Subgrade preparation Planning the sequence of installation Trenching of the GCL along the top of the slopes Rolling the GCL rolls out Joining and overlapping of the rolls, including use of paste for additional overlap protection Ensuring the cover soil is ready for placement and compaction. We have detailed installation manuals to assist you in planning your project. Should you need assistance with installation, we also offer installation frames for major projects to assist with the handling and placement of GCL rolls. Our frames are safety-rated to ensure compliance with OH&S requirements. We can also offer on-site advice for the initial period, should this be required. This is used regularly where the installation crew or project manager is inexperienced with GCL installations, and assistance from experienced people is required.
Support
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Support services We support our GCL’s with a range of support services, including – Internationally accredited laboratories with prompt response time R&D and technical support from leading industry professionals Compatibility testing of your waste or liquor with our GCL Design support (including drawings) Installation support Flexible manufacturing processes to align the products with your projects Vastly experienced engineers willing to work with you to deliver the project on-time and to specification. We regularly work with companies over a long period to develop the right containment solution for their circumstances. We regularly involve internal or external technical experts to ensure the technical characteristics of our GCL’s align with that required on-site.
If you have a project where you require some advice, then please contact us for prompt and professional assistance.
Specifications
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Specification There are many dimensions to specification of a containment structure to ensure the finished structure achieves your aims. The tools you have for controlling the goods supplied include – Compatibility testing of the waste to be contained with the sealing system Specification of the manufacturing QA testing regime Specification of the construction QA testing regime Specification of the approved laboratory standard to perform testing Working with us to understand the inter-action of the elements within the structure (e.g. how does the GCL interact with the HDPE liner or geonet etc)
We are always happy to work with clients to design a specification regime appropriate to their project aims.
Contact us for advice on the specification process.
Emerging GCL Manufacturers
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Emerging GCL Manufacturers GCL’s are not immune from the rise of global competition - BUT with everything offered at low prices– “buyer beware”. We have seen GCL manufacturers from emerging markets that do not achieve world-class standards, including the use of inferior raw materials. (For example, there are GCL’s being offered from emerging nations that use polyester fibres to reinforce the structure, as they are cheaper than polypropylene fibres. The problem is that the polyester fibres will degrade over time in the pH of the bentonite clay into which they are needled, thus the GCL will degrade over time. Unless one is aware of the influence of the raw materials within a GCL, one can easily be supplied a GCL that under-performs over time, creating problems that could have been prevented). This example can be shown for many other problems in the GCL’s from emerging nations e.g. the quality of the bentonite clay used, the reliability of the laboratory, the variation from one roll to the next etc).
We offer a long history as geosynthetic manufacturers and distributors, with the knowledge, experience and support to work with you to develop a containment solution that addresses your economic, technical and commercial requirements.
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Emerging GCL Manufacturers
The following photos of emerging GCL manufacturers from emerging nations highlight the cause for concern. The images show the lack of process control, the absence of world-class testing facilities etc – all of which increase the risk for the designer or installer.
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CONTACT DETAILS Geofabrics Australasia Pty Ltd 140 Bernard Street, Cheltenham, Victoria, 3192, Australia. Tel: +61-3-8586 9100 Fax: +61-3-8586 9174 E-mail: sales@geofabrics.com.au Website: www.geofabrics.com.au
Geofabrics International 11 Production Avenue, Molendinar, Gold Coast, 4214, Queensland, Australia. Tel: +61-7-5594 8600 Fax: +61-7-5563 3727 E-mail: exports@geofabrics.com.au Website: www.geofabricsinternational.com
Geofabrics Australasia manufacturing operation ELCO Solutions Pty Ltd 31 Activity Crescent, Molendinar, Gold Coast, 4214 Queensland, Australia.
Kaytech Engineered Fabrics P O Box 116, Pinetown, 3600, KwaZulu-Natal, South Africa. 11 Livingstone Road, Pinetown, 3610, KwaZulu-Natal, South Africa. Tel: +27-31-717 2300 Fax: +27-31-702 3173 E-mail: peter@kaytech.co.za Website: www.kaytech.co.za