Geosynthetic clay liners
Encyclopedia
Geosynthetic clay liners (or GCLs) are factory manufactured hydraulic barriers consisting of a thin layer of bentonite
(or other very low permeability material) supported by geotextile
s and/or geomembranes, being mechanically held together by needling, stitching, or chemical adhesive
s. Sodium
bentonite is the usual type, but calcium
bentonite can be modified to give a similar product.
appears to have been in the United States
in 1988 in solid waste containment as a backup to a geomembrane. The product was Claymax which is bentonite mixed with an adhesive so as to bond the clay between two geotextiles; one below (the carrier textile) and the other above (the cover textile) the bentonite in the center. About the same time a different product in Germany
, Bentofix, was manufactured by placing bentonite powder between two geotextiles and then needle punching the three-component system together.
(ISO).
or other liquids and sometimes gases. As such, they are used as replacements for either compacted clay liners or geomembranes, or they are used in a composite manner to augment the more traditional liner materials. The ultimate in liner security is probably a three component composite geomembrane/geosynthetic clay liner/compacted clay liner which has seen use as a landfill liner
on many occasions.
Bentonite
Bentonite is an absorbent aluminium phyllosilicate, essentially impure clay consisting mostly of montmorillonite. There are different types of bentonite, each named after the respective dominant element, such as potassium , sodium , calcium , and aluminum . Experts debate a number of nomenclatorial...
(or other very low permeability material) supported by geotextile
Geotextile
Geotextiles are permeable fabrics which, when used in association with soil, have the ability to separate, filter, reinforce, protect, or drain...
s and/or geomembranes, being mechanically held together by needling, stitching, or chemical adhesive
Adhesive
An adhesive, or glue, is a mixture in a liquid or semi-liquid state that adheres or bonds items together. Adhesives may come from either natural or synthetic sources. The types of materials that can be bonded are vast but they are especially useful for bonding thin materials...
s. Sodium
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...
bentonite is the usual type, but calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
bentonite can be modified to give a similar product.
History
The use of GCLs as a separate category of geosyntheticsGeosynthetics
Geosynthetics is the term used to describe a range of generally polymeric products used to solve civil engineering problems. The term is generally regarded to encompass eight main product categories: geotextiles, geogrids, geonets, geomembranes, geosynthetic clay liners, geofoam, geocells and...
appears to have been in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
in 1988 in solid waste containment as a backup to a geomembrane. The product was Claymax which is bentonite mixed with an adhesive so as to bond the clay between two geotextiles; one below (the carrier textile) and the other above (the cover textile) the bentonite in the center. About the same time a different product in Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
, Bentofix, was manufactured by placing bentonite powder between two geotextiles and then needle punching the three-component system together.
Other names
Other names used for GCLs since their initiation are “clay blankets”, “bentonite blankets”, “bentonite mats”, “prefabricated bentonite clay blankets” and “clay geosynthetic barriers”, the latter currently favored by the International Organization for StandardizationInternational Organization for Standardization
The International Organization for Standardization , widely known as ISO, is an international standard-setting body composed of representatives from various national standards organizations. Founded on February 23, 1947, the organization promulgates worldwide proprietary, industrial and commercial...
(ISO).
Function
The engineering function of a GCL is containment as a hydraulic barrier to water, leachateLeachate
Leachate is any liquid that, in passing through matter, extracts solutes, suspended solids or any other component of the material through which it has passed....
or other liquids and sometimes gases. As such, they are used as replacements for either compacted clay liners or geomembranes, or they are used in a composite manner to augment the more traditional liner materials. The ultimate in liner security is probably a three component composite geomembrane/geosynthetic clay liner/compacted clay liner which has seen use as a landfill liner
Landfill liner
A landfill liner, or composite landfill liner, is intended to be a low permeable barrier, which is laid down under engineered landfill sites...
on many occasions.