Geosynthetic clay liners (GCLs) are materials used to line landfills that incorporate a layer of bentonite clay between two layers of geosynthetic fabric. The low permeability of the bentonite clay slows the rate of liquid seepage out of the landfill. GCLs are fast and easy to install, have very low hydraulic conductivity, and can self-repair tears due to the swelling properties of bentonite. They are increasingly used as barriers in mining and industrial facilities due to their ability to form a hydraulic barrier with low permeability. GCLs consist of bentonite clay bonded between one or more layers of geosynthetic material such as geotextiles or geomembranes. The

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ABSTRACT
A geosynthetic clay liner (GCL) is a woven fabric-like material, primarily used for the lining
of landfills. It is a kind of geomembrane and geosynthetic, which incorporates a bentonite or
other clay, which has a very low hydraulic conductivity. The resulting lower permeability
slows the rate of seepage out of the landfill. Due to environmental laws, any seepage from
landfills must be collected and properly disposed of, otherwise contamination of the
surrounding ground water could cause major environmental and/or ecological problems. The
lower the hydraulic conductivity the more effective the GCL will be at retaining seepage
inside of the landfill. Bentonite composed predominantly (>70%) of montmorillonite or other
expansive clays, are preferred and most commonly used in GCLs. A general GCL
construction would consist of two layers of geosynthetics stitched together enclosing a layer
of processed sodium bentonite. Typically, woven and/or non-woven textile geosynthetics are
used, however polyethylene or geomembrane layers or geogrid geotextiles materials have
also been incorporated into the design or in place of a textile layer to increase strength.

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1. INTRODUCTION
Geosynthetic clay liners (GCLs) represent a relatively new technology that is currently
gaining acceptance as a barrier system in municipal solid waste landfill applications. GCL
technology offers some unique advantages over conventional bottom liners and covers. For
eg.GCLs are very fast and easy to install, have low hydraulic conductivity and have the
ability to self repair any rips or holes caused by the swelling properties of the bentonite from
which they are made. GCLs are low permeable materials increasingly considered for
deployment as hydraulic barriers in mining facilities and other industrial facilities. GCLs are
manufactured hydraulic barriers consisting of bentonite clay bonded to a layer, or layers, of
geosynthetic material. Bentonite is a high swelling clay that has a very low hydraulic
conductivity when hydrated with water. The primary purpose of the carrier geosynthetics is
to hold and support the bentonite such that it can be installed in a uniformly thin layer
without the loss of bentonite or changes in thickness. Unrienforced GCLs are held together
by chemical adhesives, whereas reinforced GCLs are needle-punched or stitch-bonded to
increase the shear strength of the product.
2. GEOSYNTHETIC CLAY LINERS
Geosynthetic clay liners commonly known as GCLs are woven fabric like material, primarily
used for lining of landfills. It consist of two layers of woven or non woven geosynthetics
with an intermediate layer of bentonite composite, which has very low hydraulic
conductivity.These two layers are known as carrier and cover geotextile.The bentonite can be
in the form of granular or powder. Commonly the thickness of GCL varies from 5 mm to 10
mm. They stick together together to form a composite by adhesives, needle punching, stitch
bonding or combination of them.
Geosynthetic clay liners are covered with soil after installation to protect them from stress
concentrations due to construction activities and permanent structural loads. Geosynthetic
materials can increase the characteristics of clay. The bentonite clay can be of sodium
bentonite and calcium bentonite. GCL products are produced by several large companies in

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North America, Europe, Asia. Bentonite has thick double layers and high swelling
capacity.Its lower permeability slows the seepage of covering systems.
Fig.1 Geosynthetic Clay Liners
2.1 FORMS OF GCL
 Geotextile encased is the sandwich of geotextile-clay-geotextile
 Adhesive bonded :- mixture of clay and adhesive to hold sandwich together
Eg :- Claymax 200R,Claymax 600CL
 Stitch-bonded :- held together with parallel rows of stitches
Eg :- Claymax 500SP
 Needle-punch :- held together with fibres punched through,sometimes bonded
to geotextile
Eg :- Bentomat,Bentofix
 Geomembrane-supported is the sandwich of clay and geomembrane
 Held together by adhesive mixed into clay
Eg :- Gundseal
 Bentonite swelling seals GCLs
 Self-seal at overlaps and for some other types extra bentonite is applied to overlap

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 GCLs need to be covered quickly to prevent rapid hydration,uneven swelling and
self-sealing
Fig.2 Bentofix and Bentomat
Fig.3 Claymax 200R

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Fig.4 Claymax 500SP
Fig.5 Gundseal
2.2 OTHER NAMES OF GCLs
 Clay blanket
 Bentonite blanket
 Bentonite mats
 Prefabricated Bentonite clay blanket
 Clay Geosynthetic Barriers

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3. NEEDLE-PUNCHED GCL
Needle punching is a nonwoven process by which the fibres are mechanically entangled to
produce a nonwoven fabric by repeated penetration of barbed needles through a performed
dry fibrous web. The needle board is mounted on a beam which is given an up and down
reciprocating motion by means of an eccentric crank mechanism. As a result, the fibres are
mechanically interlocked, thereby providing the mechanical strength.
Needle-punched GCLs are the commonly used type. The performance of needle-punched
GCL depends upon the durability and security of the outer layers. In this the clay core acts as
barrier component.
Fig.6 Needle-punched GCL

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4. INSTALLATION OF GCL
Operators can install GCL products much faster and easily than CCLs. Manufactureres
usually specify individual GCL installation procedures.
4.1 SURFACE AND SUBGRADE PREPARATION
The subgrade or fill material should be free of any angular or sharp rocks larger than 2 inches
(5 cm) in diameter as well as any organics or other deleterious materials. Compaction of the
subgrade should be in accordance with the design specifications, or, at a minimum, to the
extent that no rutting is caused by installation equipment or vehicles.
Prior to deployment of the BENTOMAT geosynthetic clay liner, the subgrade should be final
graded to fill all major voids or cracks and proof rolled to provide a smooth surface for the
installation of the liner. The surfaces to be lined should be smooth and free of debris, roots
and angular or sharp rocks larger than 1 inch (2.5 cm) in diameter.Minor variations in the
subgrade surface are tolerable; however, no sharp irregularities should exist. Installation over
other geosynthetic materials requires no additional surface preparation.
4.2 BENTOMAT HANDLING AND PLACEMENT
Depending on the type of subgrade at the site, the typical equipment used for deployment
may range from an extendible boom forklift to a front end loader or backhoe. Suspending the
BENTOMAT roll using a spreader bar and a core pipe through the core will facilitate
deployment and will prevent damage to the panel edges caused by the suspending chains or
straps.
Methods of deployment will vary based on site-specific conditions such as slope angle, berm
widths, the type of project, the type of subgrade surface, and the subgrade preparation. As a
general guideline, all seams should run parallel to the direction of the slope. Flat areas
require no particular orientation; however, attention should be paid to the overlap orientation
to prevent seam displacement during cover placement.

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Fig.7 extendable boom forklift
Deployment should proceed from the highest elevation to the lowest to facilitate drainage in
the event of precipitation. BENTOMAT may be deployed by pulling the material from a
suspended roll, or by weighing down one end of the roll end and then allowing it to unroll as
the installation equipment slowly moves backwards along the intended path of deployment.
4.3 SEAMING PROCEDURE
BENTOMAT seams are formed with a Volclay sodium bentonite enhanced overlap.
BENTOMAT has been engineered so that when properly installed and hydrated, a small
amount of internal sodium bentonite will extrude through the edges where overlaps exist;
however, secondary seaming measures are also recommended to insure that a continuous seal
is achieved between panels. A minimum of a 6-inch to 9-inch overlap should exist at all seam
locations. A lap line as well as a match line has been printed on the BENTOMAT panel
edges at 6 and 9 inches respectively, to ensure the proper overlap is achieved. The
BENTOMAT panels should be adjusted to smooth out any wrinkles or creases between
adjacent panels, leaving a proper seam where the overlapping panel covers the lapline of the
underlying panel but leaves the matchline exposed.

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Fig.8 GCL Overlap
4.4 ANCHORING PROCEDURE
Anchor trenches may be excavated in a number of ways, depending upon the size of the
project and the maneuvering area available at the top of the slope. The preferred methods are
to use a ditch trencher (set to the specified depth) or a small backhoe equipped with a bucket
of appropriate width. Bentomat should be placed in the trench such that the end of the panel
covers the entire trench floor but does not extend up the rear wall.The size of the anchor
trench depends on site-specific criteria such as the soil type and general condition, the angle
and length of the slope, as well as the thickness and type of proposed cover materials. In any
case, anchor trench backfill should be well compacted to prevent water intrusion or pending
and to prevent liner pullout. When using BENTOMAT in conjunction with other
geosynthetic materials, the BENTOMAT may be put in a separate trench or placed as
otherwise specified by the engineer.
4.5 PENETRATION SEALING
For sealing around penetrations, a small notch should be made around the circumference of
the pipe, into the subgrade. Volclay bentonite should then be packed around the pipe in the
notch and on adjacent areas so that the pipe is encased by a pure bentonite seal. The
BENTOMAT panel should then be placed over the penetration and slit into a "pie"

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configuration where the pipe is to protrude. This procedure will create a snug fit between the
BENTOMAT and the pipe once the laps are trimmed.
More sodium bentonite should then be spread around the cut edges of the BENTOMAT
against the pipe and over adjacent areas.
To complete the detail, a collar of BENTOMAT should be cut in a manner similar to that
made on the main panel and fit around the pipe, with additional Volclay sodium bentonite
applied into any gaps that may remain.
When Bentomat is used above or in conjunction with other geosynthetic materials, notching
below the liner may not be possible. In these cases, sprayable bituminous coatings may be
applied around the penetrations and any other critical areas. All other penetration sealing
steps should be followed to ensure a watertight seal is produced.
4.6 STRUCTURE SEALING
Another critical area in an installation is the attachment or sealing of BENTOMAT to
foundation walls, drainage outlets or concrete structures. Sealing panel edges against a wall
or foundation is accomplished with the use of pure Volclay bentonite.
To start, a small notch should be made against the edge of the object to be sealed. The notch
should be packed full of Volclay bentonite. The BENTOMAT panel is then brought up to the
structure and trimmed to fit against the wall of the structure as shown. Care must taken to
ensure that the Bentomat is kept directly against the structure as the cover material is applied.
Once hydrated, the Volclay bentonite seal will allow for settlement or other stresses that may
tend to pull the BENTOMAT from the edge.
4.7 PROTECTIVE COVER
The protective cover should be composed of well graded soils, sands or crushed gravel free
of sharp edged stones larger than 1 inch (2.5 cm) in diameter. Cover should be spread by low
ground pressure equipment.

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A minimum cover thickness of 12 inches should be kept between heavy equipment and the
liner at all times. No vehicles should drive on the BENTOMAT until proper cover has been
placed to the specified depth.Once proper depth of cover soils have been applied, compaction
equipment may be used.Care should be taken to push materials upslope wherever possible
and to avoid pinching or shifting the liner by making sharp turns or sudden stops.
4.8 ACTIVATION
For fresh water applications, the water to be contained will activate the BENTOMAT. If
highly contaminated or non-aqueous liquids are to be contained, however, the BENTOMAT
must be prehydrated with fresh water for 48 hours prior to use. Approximately one-quarter
gallon of fresh water per square foot is necessary for prehydration. Prehydration may be
accomplished by flooding the impoundment, using a sprinkler system, or by natural rainfall.
In landfill applications, the leachate is typically sufficient to hydrate the BENTOMAT.
Fig.9 GCL Role
Fig.10 GCL role fixed on spreader bar

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Fig.11 spreading of GCL
4.9 MAINTENANCE
Rips or tears may be repaired by completely exposing the affected area, removing all foreign
objects or soil, and by then placing a patch over the damage, with a minimum overlap of 12
inches on all edges.
Accessory bentonite should be placed between the patch and the repaired material at a rate of
a quarter pound per lineal foot of edge spread in a six-inch width.
If damage occurs on a slope, the same basic procedure should be used; however, the edges of
the patch should be fastened to the repaired liner with contact cement, epoxy, or some other
construction adhesive, in addition to the bentonite-enhanced seam.
Fig.12 Placing of GCL

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5. PERFORMANCE FACTORS
The key performance factors of GCLs are:
5.1 HYDRAULIC CONDUCTIVITY
Hydraulic conductivity is one of the most important criteria for soil to be used as a liner.With
the addition of GCL in the mixture the hydraulic conductivity is found to be reduced
significantly.
5.2 BEARING CAPACITY
An adequate layer of cover soil (according to the product manufacturers’ recommendations),
placed on GCLs during installation, prevents a decrease in liner thickness with the
application of a load. Without a sufficient soil layer, GCLs become compressed, raising their
hydraulic conductivity (i.e., making them more permeable) and reducing their effectiveness
as a barrier. Needle-punched GCLs are less susceptible to lateral bentonite displacement
under concentrated loads than adhesive bonded and stitch bonded.
5.3 LONG TERM RELIABILITY
The geotextile or geomembrane in GCL products remains durable for long periods of time.
5.4 SHEAR STRENGTH
Depending on the particular configuration of the barrier system, GCL technology can provide
considerable shear strength (i.e., the maximum stress a material can withstand without losing
structural integrity). In particular, a geotextile-backed GCL, with bentonite affixed via stitch
bonding, provides additional internal resistance to shear in the clay layer.
Needle-punching yields an even stronger, more rigid barrier. In addition, needle-punching
requires the use of a nonwoven geotextile on at least one side. These GCL configurations
provide enhanced interface friction resistance to the adjoining layer, an important
consideration for landfill slopes.

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5.5 SLOPE STABILITY
Comparison of the forces needed to maintain stability (eg.friction ) with the forces driving
instability (eg:soil weight) uses a Factor of Safety (FS), which is defined as the ratio of
available strength to shear stress at equilibrium.
FS > 1 means, the slaope is stable.
FS < 1 means that it is potentially unstable, and a sliding failure is possible.
5.6 FREEZE AND THAW CYCLES
Freeze and thaw cycles do not affect GCLs used in landfill bottom liner applications because
these systems are installed below the frost line. hydraulic conductivity of GCLs is not
affected by freeze and thaw cycles.
5.7 GAS PERMEABILITY AND DIFFUSION
Gas permeability and the gas diffusion coefficient decreased with increasing GCL
gravimetric water content and apparent degree of saturation. Gas permeability remains
constant and high up to 100% gravimetric water content (45% apparent degree of saturation)
and gas diffusion coefficient remains constant up to 50% gravimetric water content (20%
apparent degree of saturation) respectively.
6. ADVANTAGES AND DISADVANTAGES
6.1 ADVANTAGES
 Prevention of Root Penetration
 Increasing Resistance against Desiccation
 Lower Permeability
 Barrier against Ion Exchange
 Rapid installation/less skilled labour/low cost
 Very low hydraulic conductivity to water if properly installed

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 It can withstand large differential settlement
 Excellent self healing characteristics
 Not dependent on availability of local soils
 Field hydraulic conductivity test not required
 Easy to repair
 Reduce overburden stress on compressible substratum
6.2 DISADVANTAGES
 Loss of bentonite during placement especially for powder bentonite.
 Thin layer of GCL cause possibility to be punctured during or after installation.
 Slightly increase in hydraulic conductivity before self repair can result in escaping
leachate from the barrier.
7. RESEARCH AND RESULTS
The American Society for Testing and Materials (ASTM) has developed standardized
laboratory tests.
7.1 STANDARD TEST METHOD FOR THE MEASUREMENT OF HYDRAULIC
CONDUCTIVITY
This test method covers laboratory measurement of hydraulic conductivity (also referred to
as coefficient of permeability) of GCL with a flexible wall permeameter. Test values for
hydraulic conductivity depend on the degree of effective overburden stress around the GCL
during testing. In laboratory hydraulic conductivities of geotextile-supported GCLs vary
approximately between 10 -12 and 10-10 m/s. Hydraulic conductivity decreases as confining
stress increases.

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Fig.12
7.2 STANDARD TEST METHOD FOR MEASURING MASS PER UNIT OF GCLs
The mass per unit area is determined by weighing (oven-dried) specimens of known initial
size after drying it in an oven over a sufficient time period to remove the moisture from the
GCL.
The mass per unit area of the clay component of the GCL can be estimated by subtracting the
manufacturers reported nominal mass per unit area of the synthetic component(s) from the
total GCL mass per unit area. Test result of mass per unit area of GCL is 3.66 kg/m2 .
7.3 STANDARD TEST METHOD FOR MEASURING SELF HEALING CAPACITY
Self healing capacity of both GM-GCLs and GT-GCLs has been investigated by laboratory
leakage rate tests.
The factores affecting test results are,

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7.3.1 Overburden stress
Hydrated bentonite is squeezed into a damage hole to increase the self healing capacity. For
stress upto 200kPa, the self healing capacity increase with an increase in the value of stress.
7.3.2 Size of damage hole
A damage hole up to 30 mm diameter can be self healed.
7.4 STANDARD TEST METHOD FOR DETERMINATION OF WATER
(MOISTURE) CONTENT OF SOIL BY THE MICROWAVE OVEN METHOD
At first a moist GCL specimen is placed in a suitable container and its mass is determined.
Then it is placed in a microwave oven and subjected to an interval of drying. After that it is
taken out from the oven and its new mass is determined. This procedure is repeated until the
mass becomes nearly constant. ASTM gives the test result as 12%.
8. APPLICATIONS OF GCL
Geosynthetic clay liners are used for numerous applications around the world.
8.1 WASTE
GCLs are ideal for lining waste containment areas, such as landfills, that need the strongest
protection possible to avoid leakage and groundwater contamination.
8.1.1 Solid Waste Landfill
GCLs landfill lining system provide significantly lower permeability, improved ease of
installation and increased amount of usable space

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Fig.13 Solid Waste Landfill
8.1.2 Hazardous Waste Landfills
If hazardous waste is not properly contained, it could result in lives being endangered. GCLs
offer low permeability, chemical resistance and U.V. protection for highly reliable
containment.
Fig.14 Hazardous Waste Landfill
8.2 WATER
Water conservation is more important than ever. From canals to manmade reservoirs like
those on golf courses, GCLs provide affordable, effective protection against leakage and
damage
.
Fig.15 Application on water tailing pond
8.3 MINING
During mining process GCLs prevent the leakage of toxic gases and also provide high
durability.

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Fig.16 GCLs in mining
8.4 ENERGY
In response to increased demand for energy due to population growth and settlement of urban
areas, many companies are looking for ways to boost production at existing power plants and
explore new energy resource. GCLs provide solutions to many applications for energy
customers such as shale gas and brine, evaporation, and cooling ponds.
Fig.17 GCL in energy management
8.5 CIVIL
Geosynthetics play a pivotal role in civil engineering projects such as transportation and
retention walls. GCLs help to built roadways, control storm water, waterproof green roofs
and acts as vapour barriers.

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Fig.18 Civil works
8.6 AGRICULTURE AND AQUACULTURE
GCLs are trusted by aquaculture facilities to contain water and control its quality and by
animal farms to decrease contamination.
Fig.19 GCL in agriculture
8.7 INDUSTRIAL
GCL geomembranes, concrete protection and drainage products deliver sound control of on-
site water storage, treatment reservoirs and secondary containment.

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Fig.20 Industrial lining
9. COSTS OF GCL
Cost of installation mainly ranges from $0.05 to $0.10 per meter square.
Factors of affecting the cost of GCLs are:
 Shipping distance : as shipping distance increases cost also increases
 Size of job : incase of risky jobs cost of installation also increases
 Market demand : as all products if market demand increases, cost of installation also
increases

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10. CONCLUSION
There is no doubt that geosynthetic clay liners have gained widespread popularity over the
past decade as a substitute for compacted clay liners in cover systems. As an augmentation to
compacted clay liners in bottom liners of landfills, environmental protection barriers in
transportation facilities or storage tanks, and as single liners for canals, ponds or surface
impoundments. The lower the hydraulic conductivity the more effective the GCL will be at
retaining seepage inside of the landfill. Due to the flexibility of production and rapid
innovation, the performance of different types of GCLs may vary significantly.
GCL which has lower hydraulic conductivity, if installed properly can withstand large
differential settlement and also it has excellent self healing capacity. It does not depend on
the availability of local soils. They are easy to repair and also it reduce overburden stress on
compressible substratum. Field hydraulic conductivity test is not required for GCLs. Its
installations are also safer and long lasting. They can achieve ever-better ecological,
economical and performance-related benefits for engineers.

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REFERENCES
[1] Rouhollah Soltani Goharrizi, Fazlollah Soltani and Bahador Abolpour, 2013, “Study of
Geosynthetic Clay Liner Layers Effect on Decreasing Soil Pollution in the Bed of Sanitary
Land Fills,” published in International Journal of Water Resources and Environmental
Engineering, DOI: 10.5897/IJWREE2013.0421, Vol 5(8), August
[2] Mochamad Arief Budihardjo, Amin Chegenizadeh and Hamid Nikraz, 2012,
“Geosynthetic Clay Liner as Landfill’s Leachate Barrier,”published in International
Conference on Civil and Architectural applications (ICCAA), December
[3] Jian Yu1, Jigang Shi1 and Han Liu2, 2012, “Case Study on Application of Geosynthetic
Clay Liner in Canal Lining in Hetao Irrigation Area,” Inner Mongolia, ICID 21st
International Congress on Irrigation and Drainage,15-23 October
[4] P. Phillips and M. Eberle , The use of Geosynthetic Clay Liners (GCL's) in containment
applications, International journal Geofabrics Australasia Pty Ltd, Australia.
[5] Y.Liua,1 , A. Bouazzab,* , W.P.Gatesb,2 , R.K. Rowec,3 , 2015, “Hydraulic Perfomance of
Geosynthetic Clay Liners,” Geotextile and Geomembranes
[6] Bouazza, A. and Bowders, J. (2009). “GCLs in Waste Containment Applications,” Taylor
Francis, U.K. (in press).
[7] Rouf, M.A , Bouazza, A, Singh, R.M , Gates, W.P , Rowe, R.K, 2015, “Gas Diffusion
Coefficient and Gas Permeability of an Unsaturated Geosynthetic Clay Liner,” published in
Geosynthetics Conference 2015, February

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