Geotextiles are increasingly being used for soil stabilization in construction projects like roads and railways. They help reduce the need for aggregate and separation of different soil layers, allowing water drainage while preventing mixing. A seminar report discusses the functions, types, and applications of geotextiles. Laboratory tests on soil samples show geotextiles increase the California Bearing Ratio, a measure of soil strength. Reinforced soils had higher strength and would reduce pavement thicknesses needed. Geotextiles thus enhance subgrade performance and increase the ultimate lifespan of construction projects.

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1. INRODUCTION
Soil stabilization is an integral part to any roadway, railway, or load bearing
construction project, as poor drainage and co-mingling of materials can lead to rapid
structural disintegration and subsequent project failure. With the cost of aggregate
continuing to rise, engineers and contractors are looking for a solution that will allow
them to continue to provide the structurally sound results customers rely on, without
having to raise their prices. Geotextiles are rapidly becoming the key component to this
dilemma, as their use allows roads and other load bearing projects to be designed and
installed in much the same manner as before, with the exception being that far less
aggregate is required in order to accomplish the desired results. Geotextiles work by
separating two layers of material that need to have sustained separation in order to co-
exist in a structurally effective manner. Examples include aggregate over soil and good
soil over poor soil, both of which are common occurrences in roadway and railway
construction. They can help in a multitude of soil stabilization situations, as they perform
many different tasks, including, but not limited to:
1. Non-permanent roadways, as geotextile fabrics can be perfect for
applications such as haul roads that only need to be used for a season or
two.
2. Maintaining soil integrity in long term projects such as road building,
where it is crucial that the aggregate laid on top of the soil have a
breathable and porous layer that will allow drainage yet not allow the rock
to co-mingle with the soil. This, obviously, reduces the lifetime of the road
and can lead to premature cracking.
3. Reinforcing the soil below the geotextile fabric so as to enable it to be able
to carry high tensile loads without collapsing or spreading. This is one of
the key factors in how geotextiles can extend roadway and railway
lifespan.
4. Increasing the longevity of retaining walls by allowing the passing and
transmission of liquids and gasses through the geotextile fabric itself.

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2. GEOTEXTILES
They are permeable fabrics which, when used in association with soil, have the
ability to separate, filter, reinforce, protect, or drain.
Typically made from polypropylene or polyester, geotextile fabrics come in
three basic forms: woven (resembling mail bag sacking), needle punched
(resembling felt), or heat bonded (resembling ironed felt).
Geotextile composites have been introduced and products such as geogrids and
meshes have been developed. Geotextiles are able to withstand many things, are durable,
and are able to soften a fall if someone falls down. Overall, these materials are referred to
as geosynthetics and each configuration—geonets, geosynthetic clay liners, geogrids,
geotextile tubes, and others—can yield benefits in geotechnical and environmental
engineering design.
Fig 1: Uses of Geotextile in various places.
(Source: https://theconstructor.org)

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2.1 Types of Geotextile
Geotextiles are made up of polymers such as polyester or polypropylene. They are
divided into 3 categories on the basis of the way they are prepared;
2.1.1 Woven Fabric Geotextile
Commonly found geotextiles are of the woven type and are manufactured by
adopting the 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.
Fig 2: Woven Geotextile.
(Source: https://theconstructor.org)
2.1.2 Non-Woven Geotextile
Non-woven geotextiles are manufactured from either continuous filament yarn or
short staple fiber. The bonding of fibers is done using thermal, chemical or mechanical
techniques or a combination of techniques.

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Fig 3: Non-Woven Geotextile.
(Source: https://theconstructor.org)
Geo-fibers obtained from mechanical interlocking or chemical or thermal bonding
have a thickness of 0.5-1 mm while chemically bonded non-woven’s are comparatively
thick usually in the order of 3 mm.
2.1.3 Knitted Geotextile
Knitted geotextiles are manufactured by the process of interlocking a series of
loops of yarn together. All of the knitted geosynthetics are formed by using the knitting
technique in conjunction with some other method of geosynthetics manufacture, such as
weaving as weaving.
Fig 4: Knitted Geotextile
(Source: https://theconstructor.org)

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Apart from these three geotextiles, other geosynthetics used are geonets, geogrids,
geo-cells, geomembranes, geocomposites, etc. each having their own distinct features and
uses for special applications.
2.2 Functions of Geotextiles
The mode of operation of a geotextile in any application is defined by six
discrete functions:
Fig: 5 Geogrid functions
(Source: https://theconstructor.org)
2.2.1 Separation
The separation function of geotextile is majorly used in the construction of roads.
Geotextile prevents the intermixing of two adjacent soils. For example, by separating fine
sub grade soil from the aggregates of the base course, the geotextile preserves the
drainage and the strength characteristics of the aggregate material. Some of the applicable
areas are:
 Between sub grade and stone base in unpaved and paved roads and airfields.
 Between sub grade in railroads.
 Between landfills and stone base courses.
 Between geo membranes and sand drainage layers.

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2.2.2. Filtration
The equilibrium of geotextile-to-soil system that allows for adequate liquid flow
with limited soil loss across the plane of the geotextile. Porosity and permeability are the
major properties of geotextiles which involve infiltration action.
2.2.3. Reinforcement
Introduction of geotextile in the soil increases the tensile strength of the soil the
same amount steel does in concrete. The strength gain in soil due to the introduction of
geotextile is by the following 3 mechanisms:
 Lateral restraint through interfacial friction between geotextile and
soil/aggregate.
 Forcing the potential bearing surface failure plane to develop an alternate
higher shear strength surface.
 Membrane type of support of the wheel loads.
2.2.4 Sealing
A layer of non-woven geotextile is impregnated in between existing and new
asphalt layers. The geotextile absorbs asphalt to become a waterproofing membrane
minimizing vertical flow of water into the pavement structure
2.3 Erosion Control Applications
 Separation between different materials in order to maintain the function and
integrity.
 Reinforcement over soft soils and steep slopes
 Filtration to allow adequate liquid flow without soil loss
 Drainage via canals, dams, reservoirs and retaining walls
 Containment as a liquid or gas barrier

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3. RESULTS AND DISCUSSION
The results of the analysis of geotechnical parameters of the soil samples are
presented and subsequently discussed and for ease of discussion, the results are presented
as graphical plots and tables.
3.1. Soil Classification and Sub-Grade Rating
Figure below shows the sample graph of particle size distribution for the virgin
soils and AASHTO sub grade rating for this type of soil is ‘poor’.
Fig6: Particle size distribution for the two soil samples
(Source: AJER, Utilization of Geotextile for Soil Stabilization)
3.2. Atterbergs Limit Test
The Atterberg limits are a basic measure of the critical water contents of a fine-
grained soil: its shrinkage limit, plastic limit, and liquid limit. Liquid limit and plastic
limit of the soil sample is tested to determine its engineering properties. They had noted
that liquid limit less than 35% indicates low plasticity, between 35% and 50% indicates
intermediate plasticity, between 50% and 70% high plasticity, between 70% and 90%
very high plasticity and greater than 90% extremely high plasticity.

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3.3. Moisture Content
In the various sectors, we most often define moisture content on a dry basis. This
means that the moisture content is defined as
𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑤𝑎𝑡𝑒𝑟
𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑠𝑎𝑚𝑝𝑙𝑒
∗ 100%
The weight of the sample does not include any water. It is the weight of the
sample after it is oven-dry and all water has been removed. The weight of the water is the
difference in the weight of the sample before and after drying .The implication of high
moisture content is that the soil might exhibit a reduced strength.
3.4. Specific Gravity
The values of specific gravity for lateritic soil is 2.50 – 2.75 and clay soil is (2.60
– 2.90).This is considered to be acceptably high because it is required that soils to be used
for construction should have specific gravity that is not less than 2.25 and the mineral
composition of the crystalline rock might have contributed to the relatively high specific
gravity values.
3.5 California Bearing Ratio Test (CBR)
The CBR is a semi empirical test that is often employed in the estimation of the
bearing capacity of sub grade soils for design of pavement. It measures the resistance a
soil mass offers to the penetration of a plunger under specified density and moisture
conditions. The more difficult it is to penetrate the soil, the higher the CBR rating.
Sample results of unsoaked CBR with and without the reinforcement are presented
below. There was a considerable increase in the CBR values after the inclusion of the
non-woven geotextiles than the CBR values before the inclusion of the non-woven
geotextiles. It can be clearly seen that due to the placement of non-woven geotextile, the
CBR values increases irrespective of the placement depth. It is also observed that though
the CBR values were increased in all cases, the percentage increase was found to be
much higher when non-woven geotextile was placed at depth H/4 in the top and base

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regions for sample B but performs best at depth H/4 from the base region. The reason for
this could be attributed to the fact that the depth through which the effective pressure
bulb passes is a function of the diameter of the plunger and if the non-woven geotextile is
inserted at depths lower than the depth of pressure bulb, significant improvement can be
witnessed. Table shows a comparison between the geotechnical properties of the soil
samples with and without non-woven geotextile with the Nigerian Government standard
specification of sub grade soils for roads and bridges. Federal ministry of works and
housing recommends that soil to be used in road construction must have at least 10%
CBR value which reveals that soil samples A and B when reinforced with non-woven
geotextile satisfied the strength set for sub grade soils.
Table 1: Summary of the CBR values (Unsoaked condition)
(Source: AJER, Utilization of Geotextile for Soil Stabilization)
Fig 7: CBR values for reinforced and unreinforced soil sample
(Source: AJER, Utilization of Geotextile for Soil Stabilization)

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Fig 8: Effect of unreinforced and reinforced soil samples at depths H/4 from
top and base surfaces in the CBR mould
(Source: AJER, Utilization of Geotextile for Soil Stabilization)
3.6 COMPACTION TEST
This test was performed to establish the relationship between the Optimum
Moisture Content (O.M.C) and Maximum Dry Density (M.D.D) of the soils for a
specified compactive effort and the maximum amount of water needed to enhance the
strength or load-carrying capacity of the soil. Dry density values – moisture content
relationship sample curves for the virgin soil is presented below.
Fig 9: Dry density – Moisture content relationship of the soil samples
(Source: AJER, Utilization of Geotextile for Soil Stabilization)

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4. CONCLUSION
The principle of building roadways as for other civil engineering structures is to
determine the stresses caused by a vehicle and compare them with the parameters limit
values of the various constituent materials of the structure. This level of stress is
evaluated by a mechanical model of the pavement. The latter that researchers are trying
to develop it to make it more representative of physical reality.
Geotextiles are very important part of pavement construction regarding its
strength, durability, and working performance. They are Very useful in case of silt and
clay. According to California Bearing Ratio (CBR) Test, it was observed that when the
two soil samples were reinforced with non-woven geotextile, there was an increase in
their CBR values in unsoaked condition than when compared with their CBR values
without reinforcement which indicate that the soil samples reinforced with non-woven
geotextile are suitable for sub grade as set by the Federal Ministry of Works General
Specification (1997) criteria for sub grade soils. Also, the application of non-woven
geotextile at different depths generally increases the strength of the sub grade soil as
measured by the California Bearing Ratio (CBR) regardless the level at which the non-
woven geotextile is placed within the thickness of the sub grade. However, the depth at
which the non-woven geotextile is placed dictates its effectiveness as reinforcement as it
performs best at depth H/4 from the base surface as this gives the best increase in strength
of the soil samples which will therefore aid in reducing the cost of the pavement
thicknesses. Geotextile reinforced soils present better performance than traditional soil
under dynamic loadings. It is non-biodegradable, durable and also increases the ultimate
service life of the pavement. It should, therefore be used to enhance the performance of a
sub grade material in a pavement system.

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REFERENCES
[1] Muller, W. W.; Saathoff, F. (2015). "Geosynthetics in geo environmental
engineering”. Science and Technology of Advanced Materials. 16 (3): 034605.
[2] Barrett, R.,J(1966)., "Use of Plastic Filters in Coastal Structures,"
Proceedings from the 16th International Conference Coastal Engineers, Tokyo,
September, page no:1048–1067
[3] Madison, WI (2007), “Dane County Department of Land and Water Resources
Dane County Erosion Control and Storm water Management Manual”.
[4] “Massachusetts Department of Environmental Protection”, Massachusetts
Erosion and Sediment Control Guidelines for Urban and Suburban
Areas .Boston, MA. Page no: 73–74.
[5] Morgan, Roy P.C.; Rickson, R.J. (2011). “Slope Stabilization and Erosion
Control: A Bioengineering Approach”. London.
[6] Renfrew, Colin and Paul Bahn, (2004). Archaeology. 4th Ed. New York:
Thames.
[7] WGBH Boston (December 1996). "Interview with Stacey Loizeaux". NOVA
Online. Public Broadcasting Service.
[8] Richards, Davi (2006). "Coir is sustainable alternative to peat moss in the
garden". Garden Hints. Corvallis, OR: Oregon State University Extension
Service.
[9] Barksdale, R. D. (2006). “Potential Benefits of Geosynthetics in Flexible
Pavement Systems”. National Cooperative Highway Research Program Report
315, Washington D.C
[10] Denton, M. J. and Daniels, P. N. (2007). “Textile terms and definitions”, 11th
edition. (The Textile Institute, Manchester, U.K).
[11] Olaniyan, O. S. and Akolade, A. S. (2014). “Reinforcement of Sub grade
soils with the use of Geogrids”. International journal of Science and Research,
Vol:3,page no: 2579 – 2584

13. Seminar report 2019-20 Geotextile For Soil Stabilization
13
[12] Federal Ministry of Works and Housing (1997). “General Specification for
Roads and Bridges”. Volume II, Federal Highway Department, FMWH: Lagos,
Nigeria, page no: 317
[13] Ajibade, L. T. (2006). “A Preliminary assessment of Comparative Study of
Indigenous and Scientific Methods of Land Evaluation in Asa” L.G.A, Kwara
State, and Geo-studies Forum Vol: 3, page no: 1 – 8.
[14] AASHTO (1993),“Guide for design of pavement structures”, American
Association of State Highway and Transportation Officials, Washington DC
[15] BS 1377 (2000). “Methods of Testing Soils for Civil Engineering Purposes”.
British Standards Institute, London
[16] Koerner, R.M. (2005). “Designing with geosynthetics”. 5th edition.
[17] Prasad, S. K. (2014). “Index properties of soil”. S. J College of Engineering,
Mysore
[18] Jegede, G.A (1999). “The effect of ground water and soil Properties on
Highway Pavement failure at Ayewa locality along the IkereAdo Ekiti”.
Highway South Western Nigeria. Journal of Techno science, Vol:3,page
no:41 – 43
[19] Ogundipe, O. M. (2013). “An investigation into the use of lime-stabilized clay
as sub grade Material”. International Journal of Scientific and Technology
Research, Vol;2,page no:82 – 86
[20] Simon, A.B., Giesecke, J. and Bidlo, G (1973). Use of lateritic soil for road
construction in North Dahomey, Engineering Geology, Amsterdam. Vol: 7,
page no: 197 – 218.
[21] Woods, W. R and Adcox J. W. (2006). “A general characterization of
pavement system failures with emphasis on a method for selecting repair
process” Construct. Transport, Vol: l4, page no: 26-34.