Agru America, Inc.

Designing With Geosynthetic Clay Liners


Courtesy of Agru America, Inc.

In construction, preventing the penetration of liquids and gases is essential to maintaining the integrity of a structure. Often, containment is just as important, especially when dealing with chemical contaminants or other waste. When looking to stop the spread of contaminated liquids and gases, there are few tools as effective as geosynthetic clay liners (GCL). Read on to learn how to design barriers to liquids and gases using three types of GCL: single liners, composite liners, and composite covers.

How do you use GCL as a single liner?

A single lining, used alone with no composite or back-up geomembranes (1), is the simplest application of geosynthetic clay liners. Even this simple application has two practical uses: as a liner for canals, and as means to line underground storage tanks.

Underground storage tanks often necessitate a secondary containment liner for environmental safety in cases of failure. With a single liner GCL, you can contain the spread of liquid in the storage tank in the event of a tank burst or pipe leak. A geomembrane could also be used for this task, but GCLs have the advantage of being nearly leak proof in most situations. However, one potential area of failure can come from the choice of soil cover.

When using GCL as a single liner, it is good to keep in mind the choice of material. For example, gravel is often used to cover the area surrounding underwater tanks, and the choice of gravel can greatly affect the integrity of the GCL. Limestone, for instance, will leach calcium and magnesium down to the GCL which may cause an ion exchange that weakens the chemical composition of the liner. Prehydrating the GCL with fresh water or groundwater is one approach toward minimizing this effect.

How do you use GCL as a composite liner?

Although GCLs used as a single liner can be powerful, there are many more applications for GCL when used as a composite.

Multiple geosynthetics can be combined to tackle unique applications or as a way to augment some GCL traits. For example, the durability and hydrophobic properties of GCLs can be augmented by superimposing a geomembrane (GM) onto a sheet of GCL. This composite liner is useful for landfills and surface impoundments.

This composite liner’s improved durability and reliability allows it to be used as the primary liner of double-lined landfill facilities. Just how powerful is the GM/GCL composite versus pure GM or GM/compacted clay liner (CCL) as a liner? GM/GCL is able to greatly outperform the other approaches especially when it comes to the reduction of leakage rates.

When using GM alone, even the smallest hole brings leachate directly into the leak detection system. On the other hand, consolidation water from a GM/CCL composite is very large and difficult to distinguish from actual leakage. The GM/GCL composite attenuates any leakage through holes or flaws in the geomembrane, leading to near-zero leakage rates in many cases.

How do you use GCL as a composite cover?

Just as GM/GCL can be used as a liner under solid waste, a composite solution can be used in a cover above the solid waste. This barrier strategy for landfill covers (i.e., landfill closures or caps) can be implemented without the use of a liner beneath the waste.

Agru GeoClay® is a reinforced needle-punched geosynthetic clay liner that serves as a primary or secondary containment in composite landfill closures, mining leach pads, tailing impoundments and reclamations, and pools and lagoons. Its defining features include a self-healing and self-sealing design, efficient installation, and improved barrier design.

The material comprises a uniform layer of granular bentonite encapsulated between two nonwoven geotextiles and is ideal for moderate to steep slopes and moderate to high loads. Available in roll widths of up to 15.5’, Agru GeoClay is hydraulically superior to several feet of compacted clay. This means that Agru GeoClay can be installed with increased efficiently, thereby reducing the project’s carbon footprint. For example, a single truckload of GeoClay can cover 3/4 of an acre.

If you are interested in learning how the use of GCL can make an impact in your next construction, please reach out to an Agru representative today.

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