GCL – Geosynthetic Clay Liner
What is GCL?
GCL – Geosynthetic Clay Liner is a woven fabric like material sandwich with bentonite clay in the middle. When installed correctly it behaves like a geomembrane, resulting lower permeability slowing down any seepage out of the dam. Due to bentonite clay having a very low hydraulic conductivity it makes for an effective GCL.
A typical GCL roll construction would consist of two layers of geotextile stitched together enclosing a layer of processed sodium bentonite. Approximate thickness of GCL is 6mm.
GCL is predominately used in landfills as a backup to a geomembrane layer.
Engineering wise, GCL is containment as a hydraulic barrier to water, leachate or other liquids. GCL is used as a replacement for compacted clay liners in landfill cells and capping. For best practise liner security, a three component composite of compacted clay liner/ GCL and Geomembrane can be used.
Differences Between Geosynthetic Clay Liners and Compacted Clay Liners – Table Courtesy of Wikipedia.
| Characteristic | GCLs | CCLs |
|---|---|---|
| Material | Bentonite clay, adhesives, geotextiles and/or geomembranes | Native soils or blends of soil and bentonite clay |
| Construction | Factory manufactured and then installed in the field | Construction and/or amended in the field |
| Thickness | ~ 6 mm | 300 to 900 mm |
| Permeability of clay | 10−10 to 10−12 m/s | 10−9 to 10−10 m/s |
| Speed and ease of construction | Rapid, simple installation | Slow, complicated construction |
| Installed cost | $0.05 to $0.10 per m2 | Highly variable (estimated range $0.07 to $0.30 per m2) |
| Experience | CQC and CQA are critical | Highly workforce dependent |