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Glossary of GCL


Input Date::[2008/4/20 21:30:28]    From:Geosyntech Co.,Ltd.



activated sodium bentonite
bentonite generated from calcium bentonite through activation, with hydraulic conductivities of approx. 5 x 10-11 m/s. The water absorption capacity (after 24 hours) is approx. 600 %.


Federal Institute for Material Research and Testing, Berlin

A fine-grained swellable clay with montmorillonite as the predominant material with very low hydraulic conductivities (approx. 1 x 10-9 up to 5 x 10-12 m/s). Through the relatively large negatively charged surface (approx. up to 800 m_/g), e. g.
natural sodium bentonite has a high cation exchange capacity (approx. 80 up to 120 mval/100 g) and hence a high contaminant adsorption capacity. In geosynthetic clay liners nearly exclusively natural sodium bentonite is used, occasionally activated sodium bentonite.

bentonite mat
geosynthetic clay liner

Method to connect fibres of a
fleece to form a nonwoven. Common methods are mechanical (needle-punching ), thermal or chemical bonding .


chemically bonded nonwoven
nonwoven soaked in a fluid adhesive and dried hereafter with the fibre crossing points bonded together, creating a stiff nonwoven with low elongation and therefore susceptible to damage during installation. Chemically bonded nonwovens are rarely found in geosynthetic applications.

clay liner
geosynthetic clay liner

cohesive bonding
thermally bonded nonwoven

construction elongation
Initial elongation in the construction status without special force absorption, especially with
wovens, caused by tensile elements crossing each other and bonded without junction stiffness.

continuous fibre


A weight-per-unit-length measure (
fineness) of a yarn, filament, fibre, or other textile strand for expressing the mass in grams of 9,000 m.

German Institute for Construction Technology, Berlin

drainage layer
Three-dimensional product from
synthetic raw materials which can collect and discharge liquids and gases in the plane (see drainage).

drainage mat
geosynthetic drainage system

A weight-per-unit-length measure (
fineness) of a yarn, filament, fibre, or other textile strand for expressing the mass in grams of 10,000 m.


entangled mesh

Three-dimensional, convoluted, irregular structure of an
erosion control or drainage layer from monofilaments which are arranged directionally independent.

extruded geogrid
homogeneos geomembrane which is stretched in one or more directions to cause an orientation of the polymer molecules. This creates homogeneous tensile strengths at low strains for reinforcement applications. The stiff junctions and the force transfer to the soil is achieved by an interlocking mechanism. Due to the large cross-sectional shape of the bars, stretched geogrids achieve a higher robustness against installation loads than woven fabrics.


See geosynthetic clay liner

Multi-layered material with at least one
geotextile or geotextile-related product which takes over several functions (filtration, drainage, separation, reinforcement, packing, erosion control, protection and sealing), e. g. geosynthetic drainage system (separation, filtration, drainage; on a geomembrane additionally protection).

A planar synthetic structure consisting of a regular open network of integrally connected tensile elements, which may be linked by extrusion, bonding or interlacing (e.g.
knitted), used in contact with soil/rock and/or other geotechnical material in reinforcement applications. It is i.e. differentiated between junction stiff (welded bars) and flexible (e.g. PVC coated) geogrids.

A very low permeable material in the form of a manufactured sheet, used in geotechnical and civil engineering applications with the purpose of reducing or preventing the flow of fluid and/or vapour through the construction (see
sealing). It is differentiated between homogeneous and heterogeneous geomembranes (geomembranes are &Mac179; 1.0 mm; less than 1.0 mm are foils).

A planar synthetic material used in contact with soil/rock and/or other geotechnical material in
filtration, drainage, separation, reinforcement, protection, packing, erosion control and sealing applications.

geosynthetic clay liner
A factory assembled product of
geosynthetic materials and low hydraulic conductivity clay materials (e.g. bentonite) in the form of a sheet for sealing applications, in which the clay layer is encapsulated between geosynthetics (cover and carrier geotextile), or connected with a geosynthetic. Shear force transmitting geosynthetic clay liners are needle-punched (directional independent) or stitch-bonded (directional dependent).

geosynthetic drainage system
Three-dimensional prefabricated product manufactured from
synthetic raw materials, consisting of a drainage layer (core) which is in most cases covered with at least one geotextile filter, for liquid and/or vapour transportation.

A planar, permeable, synthetic textile material, which may be
nonwoven, knitted or woven, used in contact with soil and/or other materials in geotechnical and civil engineering applications. Geotextiles can fulfil one or more functions (filtration, separation, drainage, reinforcement, protection, packing, erosion control). Wovens, geogrids (geotextile-related product) and knitted products are usually used for reinforcement, nonwovens for filtration, separation, drainage, protection, packing, erosion control applications.

geotextile-related product
A planar, permeable, synthetic material, which does not comply with the definition of a
geotextile, used in contact with soil and/or other materials in geotechnical and civil engineering applications, e.g. geogrid.


heterogeneous geomembrane
Industrially low permeable product (liner), mostly manufactured with
synthetic raw materials, where at least one layer has to be designated as homogeneous geomembrane. One such product is e. g. a heterogeneous geomembrane with a copper sheet which additionally prevents the diffusion of chlorinated hydrocarbons.

high density polyethylene (HDPE)
Thermoplastic currently showing the best chemical resistance and excellent welding performance. HDPE has a density of approx. 0.94 – 0.96 g/cm_ and is mostly used for products in landfill engineering applications.

homogeneous geomembrane
Industrially low permeable product (liner) manufactured with
synthetic raw materials for sealing applications, such as a foil (thickness < 1.0 mm) or thermoplastic geomembrane (thickness &Mac179; 1.0 mm). The most common raw materials are polyethylene (PE), polypropylene (PP) or polyvinyl chloride (PVC).

junction stiffness
Description of the junction strength of tensile elements (e.g.
geogrid) for reinforcement in which the junctions are formed such that no displacement takes place and the tensile force transfer is optimal


knitted geotextile
A structure produced by interlooping one or more
yarns, fibres, filaments or comparable elements, mainly used for reinforcement applications.


laid geogrid

Crosswise laid tensile elements which have a flexible junction connection (e.g. with a
PVC coating) or stiff junctions in order to fulfill reinforcement tasks.

low density polyethylene (LDPE)
Thermoplastic with a lower chemical resistance and lower strength than high density polyethylene (HDPE). LDPE has a density of approx. 0.92 g/cm_ and is mainly used in agriculture applications.


mechanically bonded nonwoven
An arrangement of barbed needles creates by punching through loose
staple fibres or filaments a three-dimensionally compact nonwoven. Mechanically bonded nonwovens have a higher elongation, are less susceptible against penetration of a stone, more resistant against puncture force and have better filter properties than e.g. thermally bonded nonwovens. Due to the three-dimensional surface structure a higher interface friction can be achieved against adjacent soils.

One single
filament manufactured of the same synthetic raw material. Monofilaments with a diameter larger than 0.1 mm are usually called rod.

yarn consisting of several filaments or strands.


natural fibre

A rottable natural material such as flax, jute or cotton, which is only used for textile products if a degradation of the product is required.

natural sodium bentonite
Naturally occurring
bentonite with a high portion of sodium ions. The hydraulic conductivity of the natural sodium bentonite is in the range of < 5 x 10-11 m/s and is best suited for geosynthetic clay liners. The water absorption capacity (after 24 hours) is approx. 800 %.

needle-punched geosynthetic clay liner
An arrangement of barbed needles creates by punching through the encapsulating cover and carrier
geotextiles and the bentonite core an over the entire area direction independent shear strength transmitting geosynthetic clay liner in order to increase the low internal friction angle of the bentonite and also to encapsulate the bentonite erosion safely.

needle-punched nonwoven
mechanically bonded nonwoven

A geotextile in the form of a manufactured sheet of directionally or randomly orientated
fibres or filaments mechanically and/or thermally or chemically bonded. Nonwovens are used for filtration,drainage, separation, packing, protection and/or erosion control applications.


polyamide (PA)
Thermoplastic with a density of approx. 1.14 g/cm_. Loses by means of water absorption approx. 10 % of its strength. Polyamide is hardly used due to high raw material costs.

polyester (PET)
Thermoplastic with good chemical resistance, except in alkaline surroundings (pH > 9). Due to the high density of 1.38 g/cm_, PET is used among others for nonwoven fabrics in hydraulic engineering. Due to high strength properties and low creep behaviour, PET is also used for reinforcement applications.

polyethylene (PE)
Thermoplastic with excellent chemical resistance. In the field of geosynthetics, mostly high density polyethylene (HDPE) and low density polyethylene (LDPE) are used.

synthetic raw material

polypropylene (PP)
Thermoplastic with very good chemical resistance and a density of approx. 0.91 g/cm_. Geosynthetics from PP are used in nearly all fields of application.

polyvinyl chloride (PVC)
Thermoplastic made flexible by the use of softening agents and having a density of approx. 1.38 g/cm_. Mostly used as geomembrane where flexible liners are required. Because of the washing out of softening agents, the long-term resistance has to be examined with regard to the project specifications.

profiled surface
Surface of a
geomembrane which is formed out of the geomembrane sheet during the manufacturing process by means of profiled calender drums. Hence the profiled structure and the geomembrane are homogeneous and consist of the same raw material.





sand rough surface
Surface of a
geomembrane which is textured and where the texturing is sprayed on the surface fibrelike while the bond between the structure and the geomembrane is significantly lower than the strength of the geomembrane. Sometimes the raw materials of the structure and the geomembrane differ due to manufacture.

slit film
Cut stripes of
foil which are used in wovens as tensile element.

smooth surface
Surface of a
geomembrane which is smooth and does not have any texturing (sand rough or textured) or profile.

sodium bentonite
natural sodium bentonite

staple fibre
fibres obtained by cutting filaments which are additionally crimped. In mechanically bonded nonwovens, this three-dimensional crimping can improve among others the abrasion resistance and the friction behaviour.

stitch-bonded geosynthetic clay liner
Yarns) threads are passed through the cover geotextile, bentonite layer and carrier geotextile securing a composite product by creating a directional orientation. Therefore, the direction of shear transfer is predetermined.

An orderly assemblage of .

synthetic raw material
Chemically produced material for the production of
geosynthetics. Polypropylene (PP), polyethylene (PE), polyester (PET), polyvinyl chloride (PVC) and/or polyamide (PA) are mainly used for geosynthetics.


A weight-per-unit-length measure (
fineness) of a yarn, filament, fibre, or other textile strand for expressing the mass in grams of 1,000 m.

textured surface
Surface of a
geomembrane which is textured and in which the texturing is caused by means of bursting gas bubbles in a thinner outer skin.

thermally bonded nonwoven
By adding melting
fibres, by melting the fibre surface or by means of heat calenders (drums), fibre crossing points are thermally bonded with each other. The most usual type of production is hot-calendering. This causes relatively thin, hardly robust and rarely filter stable nonwovens. The thermal melting of the fibre crossing points makes thermally bonded nonwoven fabrics rigid (low elongation) and thus more susceptible to installation damage.

A term used to describe a plastic material that is permanently fusible. Well-known thermoplastics are
polypropylene, polyethylene, polyester, polyvinyl chloride and polyamide.

thermoplastic geomembrane
Homogeneous geomembrane manufactured with synthetics, with a minimum thickness of 1.0 mm. In German landfill engineering, nearly exclusively BAM certified HDPE geomembranes (thickness > 2.5 mm) are used for sealing applications due to their high chemical resistance. In groundwater protection, usually DIBt certified products are used in Germany. The surface may be smooth, profiled, structured or sand rough and is important for the friction behaviour.

strand, cord or bundle, designed for sewing or needlework by plying and twisting yarns.



The set of
yarns running lengthwise (machine direction) in a woven fabric

A wide film of non-bonded
fibres delivered from a cord. Several layers of a web are called fleece.

The yarn running crosswise in a

A product for reinforcement applications, manufactured by weaving
slit films, yarns or other tensile elements, usually at right angles (warp and weft direction) in a predetermined pattern to each other. Wovens have a strength which is direction dependent, and can be easier damaged during covering with coarse soil material, than relatively thicker extruded tensile elements (e.g. bars). Woven products have a product elongation which has to be overcome before tensile forces can be activated.


A generic term to describe the form of appearance and not the kind of yarn (e.g.
multifilament yarn, monofilament yarn)

yarn fineness


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