Geosynthetic Clay Liner

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Geosynthetic Clay Liner

Geosynthetic clay liner (GCLs) are gaining widespread popularity as substitutes or augmentation to compacted clay liners in landfill cover systems and composite bottom liners. GCLs are comprised of sodium bentonite clay sandwiched between layers of geotextile fabric.

GCLs swell when wet, forming a hydraulic barrier with very low permeability. They are also less susceptible to performance decreases induced by freeze-thaw and desiccation-rewetting cycles that impact CCLs.


When it comes to preventing the penetration of liquids or gases in construction, there are few tools as effective as a geosynthetic clay liner. This liner is designed to stop spills before they have a chance to escape and cause environmental damage. It is an ideal solution for adding secondary containment to spill containment berms.

GCLs are high-performance geocomposites, consisting of a pair of needle-punched geotextile layers stitched together and enclosing a layer of processed sodium bentonite for sealing. Sodium bentonite is Geosynthetic clay liner a natural sealant that has the ability to swell when in contact with water, which allows the GCL to self-heal punctures and form an impermeable barrier. This durability helps to ensure that the GCL will be able to hold up against environmental stressors, such as chemical and physical degradation.

Reinforced GCLs are also available to increase their internal shear strength, which can be a critical factor for steep slope projects. Additionally, the use of needle-punched nonwoven geotextiles provides for a stronger bond between the bentonite and the opposing geotextile, which increases both the internal shear strength and the tensile strength of the liner.

The hydraulic performance and durability of GCLs can be enhanced by replacing some of the bentonite with super-absorbent polymer. Laboratory testing has shown that GCLs containing super-absorbent polymer are more resistant to wet/dry cycle tests than GCLs without the additive.


Geosynthetic clay liner is used in a variety of environmental and civil engineering projects to contain liquids, gases and soil. They are factory manufactured hydraulic barriers consisting of a layer of low-permeability material such as bentonite, supported by geotextiles and/or geomembranes mechanically held together by needling, stitching or chemical adhesives. GCLs have gained widespread popularity over the past decade as a substitute for compacted clay liners in landfill cover systems and composite bottom liners, and as single liners for canals, ponds and surface impoundments.

The sodium bentonite clay that is utilized in the manufacture of GCLs swells when hydrated under confinement, sealing leaks and punctures. This self-healing and self-seaming property offers advantages over conventional compacted clay liners and allows for the construction of more complex final cover designs. GCLs also have much lower permeability than the underlying soil and can provide approximately the same hydraulic protection as several feet of compacted clay liner.

The needle-punched reinforced composites that comprise GCLs require less skilled labor to install and are much more cost effective compared to compacted clay liners (CCL). Additionally, they can be installed at shallower depths and minimize disruption to the underlying soil. However, slope stability concerns exist for GCL layers incorporated into complex landfill cover systems with significant slopes. In this study, laboratory direct shear tests and field observations were used to evaluate the interface shear strength of GCLs at slope interfaces with woven geotextile and textured geomembranes.

Chemical Resistance

In the context of landfills, chemical resistance refers to a material’s ability to resist degradation and/or contamination by chemicals contained in the waste material. Generally Gabion speaking, the more resistant a liner is to degradation, the more time it will be able to continue performing its engineering function of preventing leachate and contaminants from reaching groundwater or other soils.

Geosynthetic clay liners (GCLs) are factory manufactured hydraulic barriers comprised of thin layers of bentonite clay sandwiched between durable geotextiles or bonded to a geomembrane and mechanically held together through needle punching or stitch bonding. The bentonite clay used in GCLs is a naturally occurring sodium bentonite that swells when hydrated, thus providing a low permeability barrier to water and/or liquids.

When compared to traditional compacted clay liner, GCLs offer several benefits:

Ease of installation & increased air space – GCLs can be installed in less time than a conventional, thicker layer of compacted clay and have a lower weight. This translates into savings in materials, labor and transportation costs.

The hydration of the bentonite also improves GCLs chemical resistance properties. The bentonite’s natural ability to hydrate increases its crosslinking density, which in turn protects the GCL against leachate and other chemical degradation. For these reasons, GCLs are a popular solution in the containment of hazardous waste and SUDs ponds.

Secondary Containment

Many environmental laws enacted by governing agencies require that any potentially harmful seepage be confined and contained. The use of geosynthetic clay liner systems for landfill liners and SUDs pond lining is an excellent way to accomplish this task. These geosynthetic clay liners are factory-manufactured hydraulic barriers that contain the low permeability mineral sodium bentonite, or a mixture of similar materials. They are supported by a layer of geotextile or geomembrane, mechanically held together by needling, stitching or chemical adhesives.

Sodium bentonite is a natural sealant that swells when exposed to water and provides the same hydraulic protection as several feet of compacted clay. Bentofix GCLs are needle-punched reinforced composites that have a durable geotextile outer layer encapsulating a uniform core of high quality sodium bentonite. This composite is then thermally locked by controlled heat treatment to transfer shear strength to the surrounding layers of geotextile or geomembrane.

This liner system can be placed under steel tanks used to store petroleum products, chemicals or other hazardous wastes. It is also a great solution for enhancing the safety and security of storage berms, adding an additional barrier to prevent rough terrain from puncturing the primary tank or causing spills. In fact, API standards dictate that these liners be placed alongside tanks to reduce the risk of costly damage and liability in the event of leaks or tank failure.

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