--- title: "Prefabricated Geosynthetics Clay Liners" date: 2022-10-31 author: "Sales Team" url: https://oceangeosynthetics.com/products/geosynthetics-clay-liner/ --- # Prefabricated Geosynthetics Clay Liners ![Picture containing Prefabricated Geosynthetics Clay Liners](https://oceangeosynthetics.com/wp-content/uploads/2022/10/download.webp) Ocean Geosynthetics manufactures prefabricated geosynthetic clay liners (GCLs), also called bentonite clay liners: a layer of sodium bentonite held between a nonwoven and a woven polypropylene geotextile, needle punched and thermally locked. We supply 5 mm, 6 mm and 7 mm grades with a hydraulic conductivity of 2 × 10⁻¹¹ m/s, in custom grades and roll lengths, for landfill liners and caps, canals, ponds, mining and secondary containment. ## Table of Contents ## **What is a geosynthetic clay liner (GCL)?** [Geosynthetic Clay Liners](https://oceangeosynthetics.com/what-is-a-geosynthetics-clay-liner/) are factory-made hydraulic barriers: a layer of sodium bentonite encapsulated between two geotextiles. In needle-punched GCLs, fibres from one geotextile are punched through the bentonite and anchored in the other, and the three layers are then thermally locked to secure the fibres. That reinforcement lets the GCL carry shear across the bentonite, which matters on slopes. The finished product is less than one inch thick (5–7 mm for our grades) and replaces a much thicker layer of compacted clay. Like compacted clay liners, [Geosynthetic Clay Liners or GCLs](https://oceangeosynthetics.com/geosynthetic-clay-liners-or-gcls-in-landfill-engineering/) act as a hydraulic barrier: they contain water, leachate and other liquids, and in some cases gas. Unlike compacted clay, they are made under factory quality control, so the bentonite content and permeability are consistent from roll to roll. Bentonite Clay Liner, a shear-strength-transferring GCL, is one of our products. High-quality sodium bentonite is enclosed between an upper and a lower geotextile, needle punched continuously through all components and then given a controlled heat treatment to thermally lock the fibres in place for long-term shear strength. ## How a GCL seals Sodium bentonite is a natural clay sealant with a strong affinity for water. When it hydrates under confinement it can swell up to 15 times its dry volume, filling the pore space and forming a gel with very low permeability. The permeability of a fully hydrated GCL is typically around 5 × 10⁻⁹ cm/s (5 × 10⁻¹¹ m/s), about 20 times lower than the 1 × 10⁻⁷ cm/s usually required of a compacted clay liner. Ocean GCLs are rated at 2 × 10⁻¹¹ m/s by ASTM D5887. The same swelling gives GCLs their ability to self-seal at overlaps, seal around penetrations and self-heal small punctures. ## **How Ocean GCLs are made** - **Needle-punched reinforcement:** lets the GCL carry shear loads on steep slopes. A higher needle-punch density gives higher peak internal shear strength without extra processing; our 5 mm and 6 mm grades are rated at 24 kPa internal shear strength (ASTM D6243). - **Thermal locking:** heat treatment fixes the punched fibres so they do not pull out under sustained load. - **Granular bentonite:** produces less dust than powdered bentonite during installation and is less likely to shift during needle punching, so hydraulic performance stays even across the roll. - **Nonwoven cap and woven carrier:** 200–220 GSM nonwoven PP over 110–125 GSM woven PP, depending on grade (see the table below). ## **Applications** GCLs are used in [waste water](https://oceangeosynthetics.com/suitable_sectors/waste-management/), [mining](https://oceangeosynthetics.com/suitable_sectors/power-and-mining/) and [water (environment, dewatering and landfills, and hydraulic works)](https://oceangeosynthetics.com/suitable_sectors/water/) projects: - **Landfills:** as the clay component of a composite base liner under an HDPE geomembrane, and in caps. See our [Jharkhand waste management project](https://oceangeosynthetics.com/geosynthetic-clay-liner-6000-sq-mtr-and-hdpe-geomembrane-6000-sq-mtr-to-jharkhand-waste-management-project/) (GCL with HDPE geomembrane). - **Steep slopes**, where needle-punched reinforcement keeps the bentonite from shearing. - **Agribusiness:** farm ponds and irrigation storage. Read more on [Geosynthetic Clay Liner for Ponds](https://oceangeosynthetics.com/geosynthetic-clay-liner-for-ponds/). - **Coastal and river control works**, emergency and flood works. - **Mining:** heap leach pads and tailings storage. - **Oil, gas and energy:** secondary containment under tank farms. - **Transportation, infrastructure and urban infrastructure:** waterproofing behind walls and under roads near aquifers. ## **Advantages over compacted clay** **(i) Self-healing and self-seaming** Swelling bentonite closes small punctures, seals around pipes and seals overlaps between panels, so there is less chance of leaks from installation damage. **(ii) Better hydraulic performance** A GCL under one inch thick gives lower permeability than a compacted clay liner that is many times thicker, and its performance does not depend on how well clay was compacted on site. **(iii) Resistant to varying weather conditions** GCLs are less affected by freeze-thaw and wet-dry cycles than compacted clay, which tends to crack and leak more after them. A GCL gives consistent performance and does not vary with the moisture content, density or clay content achieved in the field. **(iv) Ease of installation** Most GCL projects can be installed by general construction crews with standard equipment, on slopes and over small settlements. A single 5.1 × 40 m roll covers about 204 m²; replacing that area with 90 cm of compacted clay would take about 184 m³ of clay, with the haulage and compaction that goes with it. Because the liner is so thin, it also takes up less airspace in a landfill, leaving more volume for waste. ## Limitations to design for - **Hydrate before chemical exposure.** Leachates and soils rich in calcium or magnesium can exchange with the sodium in bentonite and reduce its swelling, raising permeability. Let the GCL hydrate with clean water from the subgrade or cover soil first where possible. - **Keep it confined.** Bentonite seals most effectively under normal stress. A GCL left uncovered, or with thin cover in a cap, can dry out and crack. - **Check internal and interface shear.** Hydrated bentonite is weak; slope designs should use ASTM D6243 shear results for the actual product and interfaces. ## How to specify a GCL GRI-GCL3 is the reference specification. The main properties and test methods are: - **Swell index** (ASTM D5890): GRI-GCL3 minimum 24 mL/2 g. - **Fluid loss** (ASTM D5891): GRI-GCL3 maximum 18 mL. - **Bentonite and GCL mass per unit area** (ASTM D5993): GRI-GCL3 asks for 3,700 g/m² of bentonite measured oven-dry. Datasheets often report mass at a stated moisture content, so compare products on the same basis. - **Index flux and hydraulic conductivity** (ASTM D5887): GRI-GCL3 maximum 1 × 10⁻⁸ m³/m²/s flux or 5 × 10⁻¹¹ m/s. - **Tensile strength** (ASTM D6768) and **peel strength** (ASTM D6496) for reinforced GCLs. - **Internal and interface shear** (ASTM D6243) for slopes. Tell us the application, slope angles, overlying geomembrane and the chemistry of the liquid to be contained, and we will recommend a grade. ## Installation basics 1. Prepare a smooth, firm subgrade free of stones, roots and standing water. 2. Unroll panels with the correct side up (usually nonwoven side towards the geomembrane or cover soil), running down slopes, not across them. 3. Overlap adjacent panels by the amount in the manufacturer’s installation guide, with larger overlaps at roll ends; add granular bentonite at overlaps where the guide calls for it. 4. Do not install in rain or let panels hydrate before they are covered; replace any panel that hydrated while unconfined. 5. Cover the same day with the geomembrane or with cover soil, typically at least 300 mm, placed with light equipment that does not run directly on the GCL. ASTM D6102 is the standard guide for GCL installation. For a composite liner, the overlying [HDPE geomembrane](https://oceangeosynthetics.com/products/ocean-geomembrane/) goes directly on the GCL. ## Frequently asked questions ### Can a GCL replace compacted clay in a landfill liner? Often, yes, subject to approval by the pollution control board. The Solid Waste Management Rules, 2016 specify 1.5 mm HDPE over 90 cm of clay with permeability no more than 1 × 10⁻⁷ cm/s, and a GCL is commonly proposed as the clay component or in addition to it. ### What is the hydraulic conductivity of Ocean GCL? 2 × 10⁻¹¹ m/s by ASTM D5887 for all three grades. ### Does a GCL need a geomembrane on top? Not always. GCLs are used alone in ponds, canals and secondary containment, but landfills and chemical containment normally pair them with an HDPE geomembrane as a composite liner. ### What roll size do you supply? Standard rolls are 5.1 m × 40 m (5.15 m × 40 m for the 7 mm grade). Custom grades and roll lengths are available. ### How should GCL rolls be stored on site? Off the ground, under cover and in their wrapping until use, so the bentonite stays dry. ## Technical Specifications ### Technical Specifications of Ocean GCL | Property | Unit | Test Method | 5 MM | 6 MM | 7 MM | | --- | --- | --- | --- | --- | --- | | Cap Nonwoven PP Mass Per Unit Area | GSM | EN ISO 9864 / EN965 | 200 | 200 | 220 | | Carrier Woven PP Mass Per Unit Area | GSM | EN ISO 9864 / EN965 | 125 | 125 | 110 | | Montmorillonite Content | % | XRD Analysis | 85 | 85 | – | | Swell Index | ML/2G | ASTM D5890 | 25 | 25 | 24 | | Fluid Loss | ML | ASTM D5891 | 17 | 17 | <18 | | Bentonite Mass Per Unit Area (12% Moisture) | GSM | EN 14196 / EN965 | 4000 | 4000 | 3670 | | GCL Mass Per Unit Area (12% Moisture) | GSM | EN 14196 / ASTM D5993 | 4325 | 4325 | 4000 | | Hydraulic Conductivity (K20) | M/S | ASTM D5887 | 2×10-11 | 2×10-11 | 2×10-11 | | Index Flux (Q) | (M3/M2)/S | ASTM D5887 | 5×10-9 | 5×10-9 | 1×10-8 | | Tensile Strength MD (TMAX) | KN/M | ASTM D6768 / D4595 | 12 | 12 | 12 | | Tensile Strength CMD (TMAX) | KN/M | ASTM D6768 / D4595 | 12 | 12 | 12 | | Static Puncture Strength (FP) | KN | EN ISO 12236 | 2.2 | 2.2 | – | | Internal Shear Strength | KPA | ASTM D6243 | 24 | 24 | – | | Thickness | MM | EN ISO 9863 / EN 964-1 | 5 | 6 | 6.0 | | Roll Dimensions (H x L) | M | – | 40 x 5.1 | 40 x 5.1 | 5.15 x 40 | ## Key Applications - Landfill basal liners and caps - Canals and reservoirs - Aquifer protection - Industrial and wastewater lagoons - Heap leach pads and tailings storage - Secondary containment berms - Vertical cutoff trenches for groundwater control - Landfill caps with gas and VOC containment ## Key Features - Factory-fabricated hydraulic barrier with high-quality sodium bentonite - Ultra-low permeability and self-sealing when confined and hydrated - Needle punched and thermally locked for high internal shear strength - Self-seals overlaps, small punctures and penetrations - Rapid installation versus compacted clay - Secure placement on steep slopes - Resilient through freeze-thaw and wet-dry cycles with reduced cracking [Download Clay Liner Brochure (PDF)](https://oceangeosynthetics.com/wp-content/uploads/2026/06/clay-liner-brochure.pdf) - [![](https://oceangeosynthetics.com/wp-content/uploads/2022/10/IMG_8925-1024x683.webp)](https://oceangeosynthetics.com/wp-content/uploads/2022/10/IMG_8925.webp) - [![](https://oceangeosynthetics.com/wp-content/uploads/2022/10/IMG_8930-1024x683.webp)](https://oceangeosynthetics.com/wp-content/uploads/2022/10/IMG_8930.webp) - 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