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Seminar Report 2018-19 Geosynthetic
Dept. of Civil Engg. 1 GPTC Mananthavady
INTRODUCTION
Geosynthetic product manufactured from polymeric material used with
soil, rock, earth or other geotechnical related material as an integral part of civil
engineering project. Geosynthetics can be defined as planar products
manufactured from polymeric material, which are used with soil, rock, or other
geotechnical engineering-related material as an integral part of a man-made
project, structure, or system. Geosynthetics are widely used in many geotechnical
and environmental applications related to groundwater quality and control. This is
the case, for example, of base and cover liner systems for modern landfills, which
are designed making extensive use of geosynthetics. The main purpose of
geosynthetic liner systems is to minimize potential groundwater contamination.
Moreover, the use of geosynthetics is rapidly increasing in applications related
directly to groundwater control. This is the case of high-density polyethylene
(HDPE) vertical barrier systems, which are used instead of traditional soil-
bentonite cutoff walls in projects involving groundwater remediation and control.
The geosynthetics market is strong and rapidly increasing because of the
continued use of geosynthetics in well-established applications and, particularly,
because of the increasing number of new applications which make use of these
products. Geosynthetics were used in roadway construction in the days of the
Pharaohsto stabilise roadways and their edges. These early geosynthetics were
made of natural fibres, fabrics or vegetation mixed with soil to improve road
quality, particularly when roads were made on unstable soil. Only recently have
geosynthetics been used and evaluated for modern road construction.
geosynthetics today are highly developed products that must comply with
numerous standards.

IMPORTANT CHARACTERISTICS OF GEOSYNTHETICS
The characteristics of geosynthetics are broadly classified as:
1. Physical properties
a) Specific gravity
b) Weight
c) Thickness
2. Mechanical properties
a) Tenacity
b) Tensile strength
c) Bursting strength
d) Drapability
e) Compatibility
3. Hydraulic properties
a) Porosity
b) Permeability
c) Permittivity
d) Transitivity
4. Degradation properties
a) Biodegradation
b) Hydrolytic degradation
c) Photo degradation
d) Chemical degradation
5. Endurance properties
a) Elongation
b) Abrasion resistance

DIFFERENT TYPES OF GEOSYNTHETICS
Geosynthetics are manufactured in a factory-controlled environment. They
are packaged in sheets, placed in a roll or carton, and finally transported to the
site. At the project site the geosynthetic sheets are unrolled on the prepared
subgrade surface, overlapped to each other to form a continuous geosynthetic
blanket, and often physically joined to each other.
The geosynthetic types are as follows:
 Geotextiles
 Geogrids
 Geonent
 Geomembrane
 Geosynthetic clay liners (GCLs)
 Geoform
 Geocells
 Geocomposites
 GEOTEXTILE
Geotextiles were one of the first textile products in human history.
Excavations of ancient Egyptian sites show the use of mats made of grass and
linen. Geotextiles were used in roadway construction in the days of the
Pharaohsto stabilise roadways and their edges. These early geotextiles were made
of natural fibres, fabrics or vegetation mixed with soil to improve road quality,
particularly when roads were made on unstable soil. Only recently have
geotextiles been used and evaluated form Modern road construction. Geotextiles

today are highly developed products that must comply with numerous standards.
To produce tailor-made industrial fabrics, appropriate machinery is needed.
 SELECTION OF FIBER FOR GEOTEXTILES
Different fibres from both natural as well as synthetic category can be used
as geotextiles for various applications. Natural fibres: Natural fibers in the form of
paper strips, jute nets, wood shavings or wool mulch are being used as geotextiles.
In certain soil reinforcement applications, geotextiles have to serve for more than
100 years. But bio-degradable natural geotextiles are deliberately manufactured to
have relatively short period of life. They are generally used for prevention of soil
erosion until vegetation can become properly established on the ground surface.
The commonly used natural fibres are –
Ramie: These are subtropical bast fibres, which are obtained from their plants 5
to 6 times a year. The fibres have silky luster and have white appear uneven in the
unbleached condition. They constitute of pure cellulose and possess highest
tenacity among allplant fibres.
Polyamides (PA): There are two most important types of polyamides, namely
Nylon 6 and Nylon 6,6 butthey are used very little in geotextiles. The first one an
aliphatic polyamide obtained by the polymerization of petroleum derivative ε-
caprolactam. The second type is also an aliphatic polyamide obtained by the
polymerization of a salt of adipic acid and hexamethylene diamine. These are
manufactured in the form of threads which are cut into granules. They have more
strength but less moduli than poly propylene and polyester They are also readily
prone to hydrolysis.
Polyesters (PET): Polyester is synthesised by polymerizing ethylene glycol with
dimethyleterephthalate or with terephthalic acid. The fibre has high strength
modulus, creep resistance and general chemical inertness due too which it is more
suitable for geotextiles. It is attacked by polar solvent like benzyl alcohol, phenol,
and meta-cresol. At pH range of 7 to 10, its life span is about 50 years. It

possesses high resistance to ultraviolet radiations. However, the installation
should be undertaken with care to avoid unnecessary exposure to light.
Polyvinyl chloride (PVC): Polyvinyl chloride is mainly used in geo membranes
and as a thermo plastic coating materials. The basic raw materials utilized for
production of PVC is vinyl chloride. PVC is available in free- flowing powder
form.
Chlorinated Polyethylene (CPE): Sealing membranes based on chlorinated poly
ethylene are generally manufactured from CPE mixed with PVC or sometimes
PE. The properties of CPE depend on quality of PE and degree of chlorination.
Types of Geotextiles
Geotextiles are a permeable synthetic material made of textile materials.
They are usually made from polymers such as polyester or polypropylene. The
geotextiles are further prepared in three different categories – woven fabrics, non-
woven fabrics.
Woven fabrics: Large numbers of geosynthetics are of woven type, which
can be sub-divided into several categories based upon their method of
manufacture. These were the first to be developed from the synthetic fibers. As
their name implies, they are manufactured by adopting techniques which are
similar to weaving usual clothing textiles. This type has the characteristic
appearance of two sets of parallel threads or yarns .the yarn running along the
length is called warp and the one perpendicular is called weft. The majority of low
to medium strength woven geosynthetics are manufactured from polypropylene
which can be in the form of extruded tape, silt film, monofilament or
multifilament. Often a combination of yarn types is used in the warp and weft
directions to optimize the performance/cost. Higher permeability is obtained with
monofilament and multifilament than with flat construction only.Woven
Geotextile.

Non-woven: Non woven geo-synthetics can be manufactured from either
short staple fibre or continuous filament yarn. The fibers can be bonded together
by adopting thermal, chemical or mechanical techniques or a combination of
techniques. The typeof fibre (staple or continuous) used has very little effect on
the properties of the non – woven geosynthetics. Non-woven geotextiles are
manufactured through a process of mechanical interlocking or chemical or
thermal bonding of fibres/filaments. Thermally bonded non-wovens contain wide
range of opening sizes and a typical thickness of about 0.5-1mm while chemically
bonded non-wovens are comparatively thick usually in the order of 3 mm. On the
other hand mechanically bonded non-woven shave a typical thickness in the range
of 2-5 mm and also tend to be comparatively heavy because a large quantity of
polymer filament is required to provide sufficient number of entangled filament
cross wires for adequate bonding.
 GEONETS
Geonets, and the related geospacers by some, constitute another specialized
segment within the geosynthetics area. They are formed by a continuous extrusion
of parallel sets of polymeric ribs at acute angles to one another. When the ribs are
opened, relatively large apertures are formed into a netlike configuration. Two
types are most common, either biplanar or triplanar. Alternatively many very
different types of drainage cores are available. They consist of nubbed, dimpled or
cuspated polymer sheets, three-dimensional networks of stiff polymer fibers in
different configurations and small drainage pipes or spacers within geotextiles.

Their design function is completely within the drainage area where they are used
to convey liquids or gases of all types.
 GEOGRIDS
Geogrids represent a rapidly growing segment within geosynthetics. Rather
than being a woven, nonwoven or knitted textile fabric, geogrids are polymers
formed into a very open, gridlike configuration, i.e., they have large apertures
between individual ribs in the transverse and longitudinal directions. Geogrids are
(a) either stretched in one, two or three directions for improved physical
properties, (b) made on weaving or knitting machinery by standard textile
manufacturing methods, or (c) by laser or ultrasonically bonding rods or straps
together. There are many specific application areas; however, geogrids function
almost exclusively as reinforcement materials.

 GEOMEMBRANES
Geomembranes represent the other largest group of geosynthetics, and in
dollar volume their sales are greater than that of geotextiles. Their growth in the
United States and Germany was stimulated by governmental regulations
originally enacted in the early 1980s for the lining of solid-waste landfills. The
materials themselves are relatively thin, impervious sheets of polymeric material
used primarily for linings and covers of liquids- or solid-storage facilities. This
includes all types of landfills, surface impoundments, canals, and other
containment facilities. Thus the primary function is always containment as a
liquid or vapor barrier or both. The range of applications, however, is great, and in
addition to the environmental area, applications are rapidly growing in
geotechnical, transportation, hydraulic, and private development engineering
(such as aquaculture, agriculture, heap leach mining, etc.).
GEOSYNTHETIC CLAY LINERS
Geosynthetic clay liners, or GCLs, are an interesting juxtaposition of
polymeric materials and natural soils. They are rolls of factory fabricated thin
layers of bentonite clay sandwiched between two geotextiles or bonded to a
geomembrane. Structural integrity of the subsequent composite is obtained by
needle-punching, stitching or adhesive bonding. GCLs are used as a composite
component beneath a geomembrane or by themselves in geo environmental and
containment applications as well as in transportation, geotechnical, hydraulic, and
many private development applications.

 GEOFOAM
Geofoam is a product created by a polymeric expansion process of polystyrene
resulting in a “foam” consisting of many closed, but gas-filled, cells. The skeletal
nature of the cell walls is the unexpanded polymeric material. The resulting
product is generally in the form of large, but extremely light, blocks which are
stacked side-by-side providing lightweight fill in numerous applications.
 GEOCELLS
Geocells (also known as Cellular Confinement Systems) are three-dimensional
honeycombed cellular structures that form a confinement system when in filled
with compacted soil. Extruded from polymeric materials into strips welded
together ultrasonically in series, the strips are expanded to form the stiff (and
typically textured and perforated) walls of a flexible 3D cellular mattress. In filled
with soil, a new composite entity is created from the cell-soil interactions. The
cellular confinement reduces the lateral movement of soil particles, thereby

maintaining compaction and forms a stiffened mattress that distributes loads over
a wider area. Traditionally used in slope protection and earth retention
applications, geocells made from advanced polymers are being increasingly
adopted for long-term road and rail load support. Much larger geocells are also
made from stiff geotextiles sewn into similar, but larger, unit cells that are used
for protection bunkers and walls.
 GEOCOMPOSITES
A geocomposite consists of a combination of geotextiles, geogrids, geonets
and/or geomembranes in a factory fabricated unit. Also, any one of these four
materials can be combined with another synthetic material (e.g., deformed plastic
sheets or steel cables) or even with soil. As examples, a geonet or geospacer with
geotextiles on both surfaces and a GCL consisting of a
geotextile/bentonite/geotextile sandwich are both geocomposites. This specific
category brings out the best creative efforts of the engineer and manufacturer. The
application areas are numerous and constantly growing. The major functions
encompass the entire range of functions listed for geosynthetics discussed
previously: separation, reinforcement, filtration, drainage, and containment.

FUNCTIONS OF GEOSYNTHETICS
Geosynthetics have numerous material properties. Many of the reported
properties are important in the manufacture and quality control of geosynthetics;
however, many others are also important in design. The material properties related
to the manufacture and quality control of geosynthetics are generally referred to as
index properties and those related to the design as design or performance
properties. Considering their different properties, the several geosynthetic
products can perform different functions and, consequently, they should be
designed to satisfy minimum criteria to adequately perform these functions.
The geosynthetic functions are as follows:
• Separation
• Reinforcement
• Filtration
• Drainage
 Containment
Separation is the placement of a flexible geosynthetic material, like a porous
geotextile, between dissimilar materials so that the integrity and functioning of
both materials can remain intact or even be improved. Paved roads, unpaved
roads, and railroad bases are common applications. Also, the use of thick
nonwoven geotextiles for cushioning and protection of geomembranes is in this
category. In addition, for most applications of geofoam and geocells, separation is
the major function.
Reinforcement is the synergistic improvement of a total system’s strength created
by the introduction of a geotextile, geogrid or geocell (all of which are good in

tension) into a soil (that is good in compression, but poor in tension) or other
disjointed and separated material. Applications of this function are in
mechanically stabilized and retained earth walls and steep soil slopes; they can be
combined with masonry facings to create vertical retaining walls. Also involved is
the application of basal reinforcement over soft soils and over deep foundations
for embankments and heavy surface loadings. Stiff polymer geogrids and geocells
do not have to be held in tension to provide soil reinforcement, unlike geotextiles.
Stiff 2D geogrid and 3D geocells interlock with the aggregate particles and the
reinforcement mechanism is one of confinement of the aggregate. The resulting
mechanically stabilized aggregate layer exhibits improved loadbearing
performance. Stiff polymer geogrids, with very open apertures, in addition to
three-dimensional geocells made from various polymers are also increasingly
specified in unpaved and paved roadways, load platforms and railway ballast,
where the improved loadbearing characteristics significantly reduce the
requirements for high quality, imported aggregate fills, thus reducing the carbon
footprint of the construction.
Filtration is the equilibrium soil-to-geotextile interaction that allows for adequate
liquid flow without soil loss, across the plane of the geotextile over a service
lifetime compatible with the application under consideration. Filtration
applications are highway underdrain systems, retaining wall drainage, landfill
leachate collection systems, as silt fences and curtains, and as flexible forms for
bags, tubes and containers.
Drainage is the equilibrium soil-to-geosynthetic system that allows for adequate
liquid flow without soil loss, within the plane of the geosynthetic over a service
lifetime compatible with the application under consideration. Geopipe highlights
this function, and also geonets, geocomposites and very thick geotextiles.
Drainage applications for these different geosynthetics are retaining walls, sport
fields, dams, canals, reservoirs, and capillary breaks. Also to be noted is that
sheet, edge and wick drains are geocomposites used for various soil and rock
drainage situations.

Containment involves geomembranes, geosynthetic clay liners, or some
geocomposites which function as liquid or gas barriers. Landfill liners and covers
make critical use of these geosynthetics. All hydraulic applications (tunnels,
dams, canals, surface impoundments, and floating covers) use these geosynthetics
as well.

ADVANTAGES
 The manufactured quality control of geosynthetics in a controlled factory
environment is a great advantage over outdoor soil and rock construction.
Most factories are ISO 9000 certified and have their own in-house quality
programs as well.
 The low thickness of geosynthetics, as compared to their natural soil
counterparts, is an advantage insofar as light weight on the subgrade, less
airspace used, and avoidance of quarried sand, gravel, and clay soil
materials.
 The ease of geosynthetic installation is significant in comparison to thick
soil layers (sands, gravels, or clays) requiring large earthmoving
equipment.
 Published standards (test methods, guides, and specifications) are well
advanced in standards-setting organizations like ISO, ASTM, and GSI.
 Design methods are currently available from many publication sources as
well as universities which teach stand-alone courses in geosynthetics or
have integrated geosynthetics in traditional geotechnical,
geoenvironmental, and hydraulic engineering courses.
 When comparing geosynthetic designs to alternative natural soil designs
there are usually cost advantages and invariably sustainability (lower CO2
footprint) advantages

DISADVANTAGES
 Long-term performance of the particular formulated resin being used to
make the geosynthetic must be assured by using proper additives including
antioxidants, ultraviolet screeners, and fillers.
 The exposed lifetime of geosynthetics, being polymeric, is less than
unexposed as when they are soil backfilled.
 Clogging or bioclogging of geotextiles, geonets, geopipe and/or
geocomposites is a challenging design for certain soil types or unusual
situations. For example, loess soils, fine cohesionless silts, highly turbid
liquids, and microorganism laden liquids (farm runoff) are troublesome and
generally require specialized testing evaluations.
 Handling, storage, and installation must be assured by careful quality
control and quality assurance.

CONCLUSION
Geosynthetics are not only clothing the human body but also our mother
land in order to protect her. Extensive awareness should be created among the
people about the application of geosynthetics. Geosynthetics are effective tools in
the hands of the civil engineer that have proved to solve a myriad of geotechnical
problems. To explore the potential of geosynthetics more researches are needed in
this field.

REFERENCES
1. ASTM (1994), Annual Books of ASTM Standards, American Society
Testing and
1. Materials, Philadelphia, Pennsylvania. Volume 4.08 (1), Soil and Rock,
Volume 4. No. (8), Soil and Rock, Geosynthetics, Volume 7, No.
1,Textiles.
2. Abdullah, A. B. M., A Hand book of geosynthetics Particularly natural
geosynthetics from jute and other vegetable fibers, FAO-2000
3. Gregory, R. N., Barry, C. R., Geosynthetics in Transportation Applications,
Featured Short Course, 1998.
4. Rankilor, P. R., Membranes in Ground Engineering, John Wiley and Sons,
New York,1981.
5. Koerner, R. M., Designing with Geosynthetics, Third edition, Prentice
Hall, 1993.

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