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.

GCL rolls sizes

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