Geosynthetic Clay Liners

Geosynthetic clay liners (GCLs) are an established sealing product in the geoenvironmental industry. They are used in landfill caps and base liner applications under roads, railways, secondary containment for above ground tank farms, as well as within various other containment structures such as dams, canals, ponds, rivers and lakes. They are also used for waterproofing of buildings and other similar structures.

Rolled out like a carpet to provide a durable impermeable liner, geosynthetic clay liners consist of a layer of high swelling sodium bentonite, sandwiched between two geotextiles. By different techniques, GCL is mechanically bonded by needlepunching from one nonwoven geotextile through the bentonite to the other nonwoven or woven geotextile.

Sodium ions located between these platelets allow water to hydrate the bentonite in an absorption reaction that results in the bentonites swelling characteristics. Swells when contacted with water approximately 900% by volume or 700% by weight. When hydrated under confinement, the bentonite swells to form a low permeability clay layer with the equivalent hydraulic protection of several feet of compacted clay.

This swelling allows the bentonite to seal around penetrations, giving the GCL self-sealing characteristics. During hydration, a confined layer of dry bentonite changes into a dense monolithic mass with no observable individual particles. A fully hydrated sodium bentonite layer can have a hydraulic conductivity of approximately one hundred times lower than a typical compacted clay liner (CCL).

Because of their low hydraulic conductivity, GCLs are used mainly as a replacement for thick, difficult to build, compacted clay liners to provide a barrier to liquids and gases.

Permathene supply and install a range of GCL's from light to heavy grades. These are high performance environmental liner comprised of geosynthetic carrier components integrated with a layer of low permeability sodium bentonite. The rolls are supplied in wide widths, minimizing seams. Installation is fast.

Usage

Mainly used in environment engineering of landfill emissions, water reservoirs, underground infrastructure construction projects, sealing solution, segregation, anti-leakage, good effect, anti-destructive.

BENTAMAT (GCL)
EXPLAINATION OF CONSTRUCTION

A) BASIC REQUEST

1. Basement soil should be massively compacted (density≥85%), in case its disadvantages for permanent use, during the application process.
   
2. Preventing GCL from being damaged to make sure its waterproof effect, the basement soil should be even and should not have these sharp pointed things such as stone with diameter more than 50mm.If this is impossible, we suggest that the level layer should be made of medium sand with thickness of 300mm or cement mortar instead whose thickness ranges from 30mm to 50mm.
   
3. The GCL can be constructed under the damp environment, but should not be dipped in water.
   
4. If basement soil bottom elevation is lower than the groundwater level, effective measures should be taken to drain up the water.

B) GCL’S LAYING

1. Connect in accordance with the water follow direction, that is, GCL in upstream connect with that of the downstream.
   
2. The lap joint should be even and the lap over should be more than 300mm.
   
3. Bentamat powder about 0.2kg or 0.3kg /m should be scattered evenly in the lap joint.
   
4. Considering the basement soil may sink or deform, if possible fold GCL at the bottom one or two, whose length is 100mm.
   
5. The non-woven geotextile layer should be laid upper and the angle between bottom and slope should less than 30°.These GCL on the slope should be fixed with nails.
   
6. During laying, GCL’s edge should be laid 100mm higher than the designed water level.
   
7. If it is essential that the wire or pile tip should penetrate through GCL, a piece of complete GCL should be first laid according to the pipe with extra diameter of 300mm.Some paste mixture that made of GCL powder and water should be daubed around the pipe.
   
8. If GCL is damaged or the joint is too complex to connect, upon it we can use one piece of complete GCL, with extra 300mm diameter than its area to cover. Between the overlaps some GCL powder should be scattered.

C) Fixation of GCL

1. If the slope is revetment naturally and there are anchored ditch around the river or lake, which is 300mm in depth and 500mm in width or more than that .Put the GCL edge into anchored ditch then fill it with soil.
   
2. When GCL is perpendicular to anchored ditch, fix it with steel nail together with other GCL around.