Geotextiles are permeable fabrics used in soil applications to separate, filter, reinforce, protect, or drain, and can be made from woven, needle punched, or heat bonded materials. Their key functions include filtration, drainage, separation, reinforcement, and sealing, applicable in various construction contexts like flexible paved roads and drainage systems. The selection of geotextiles depends on design properties like puncture strength, permeability, and tensile strength, making them an efficient solution for geotechnical challenges in road engineering.

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2. INTRODUCTION
 Geotextiles 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 (looks like mail bag sacking)
• needle punched (looks like felt)
• heat bonded (looks like ironed felt).

4. FUNCTIONS OF GEOTEXTILES
 Filtration
 Drainage
 Separation
 Reinforcement
 Sealing

6. FILTRATION
The equilibrium geotextile to soil
system that allows for adequate
liquid flow with limited soil loss
across the plane of geotextile over
a service lifetime.

7. DRAINAGE/TRANSMISSIVITY
Ability of thick nonwoven geotextile
whose 3-dimensional structure
provides an avenue for flow of water
through the plane of the geotextile.

8. SEPARATION
The introduction of a flexible porous textile placed between dissimilar
materials so that the integrity and functioning of both the materials can
remain intact or be improved.

9. REINFORCEMENT
Geotextile acts as a reinforcing element in
a soil mass or in combination with the soil
to produce a composite that has improved
strength and deformation properties.

10. SEALING
• The classic application of a geoxtile
as a liquid barrier is paved road
rehabilitation.
• It minimizes vertical flow of water
into the pavement structure.

11. TYPES OF GEOTEXTILES
Woven fabrics
Non-woven fabrics
Knitted fabrics

12. DESIGN PROPERTIES
 Puncture Strength
 Burst Strength
 Dynamic Puncture
 Permeability
 Apparent Opening Size (AOS)
 Grab Tensile Strength and Elongation

13. PUNCTURE STRENGTH
 To measure puncture resistance
 Stimulates puncture strength to static load of aggregates
 Resistance to puncture measured in Newton

14.  Stimulates strength of geotextile to a continuous hydraulic load
 Force causing rupture recorded in units of pounds per square inch or kilo
Pascal.
BURST STRENGTH

15. DYNAMIC PUNCTURE
 To measure the strength of geotextile to falling objects.
 Stimulates placement of aggregate over geotextile during installation
stage.
 Expressed in mm.

16. PERMEABILITY
 Measures the rate at which liquids can pass through the geotextile
 x=k/t
x- geotextile permittivity (sec-1)
k- geotextile permeability(cm/sec)
t- geotextile thickness (mm)
 Expressed in liters per square meters per second

17. APPARENT OPENING SIZE (AOS)
 Reflects approximate largest opening dimension available through which
the soil may pass.
 Expressed in mm.

18. GRAB TENSILE STRENGTH AND
ELONGATION
 Measures tensile strength and elongation along the plane of the
geotextile by loading it continually
 Value of breaking load expressed in Newton and elongation at break in
percent.

19. AREAS OF APPLICATION
• Flexible paved road construction
• Drainage applications
• Pavement overlays

20. FLEXIBLE PAVED ROAD CONSTRUCTION
Function of geotextiles:
• service life of roads
• load carrying capacity
• rutting

21. RESEARCHES ON GEOTEXTILE
For weak subgrades (CBR=2%)
 Service life by a factor of 2.5-3.0
 AASHTO structural number by 19%
For moderate strength (CBR=4.2-4.5%)
 Service life by a factor of 2.0-3.3
 AASHTO structural number by 13-22%

22. AASHTO DESIGN METHOD
Excellent drainage
 SNeff
 Drainage factor - 1.20
Poor drainage
 SNeff
 Drainage factor as 0.60

23. GEOTEXTILE REQUIREMENT
Selection of geotextile
 Depends on survivability
 Governed by anticipated construction stresses

25. PAVEMENT OVERLAYS
Benefits of using Fabric Interlayer
 Waterproofing of the lower layers
 Retarding reflection cracking in the overlay
 Increase in structural stability
 Absorption of stresses

27. CAPABILITIES OF PAVING FABRICS:-
 Reduces permeability of a pavement
 Reduces infiltration of moisture
 Maintains the strength of subgrade, sub base and base course
 Limiting damage due to saturated condition pore pressures

28. PROPERTIES OF PAVING FABRICS
 Nonwoven fabrics from grades ranging from 135gm/m² to
200gm/m²
 Lighter fabrics are moisture barriers
 Heavier fabrics provides cushioning or stress-relieving
membrane

29. INSTALLATION PROCEDURE
• The surface is cleaned
• Cracks are filled or repaired
• Tack coat ranging from 1-1.35 l/m² of residual asphalt is evenly
applied
• The paving fabric is laid with minimum wrinkles
• Finally hot mix overlay is placed

31. DRAINAGE
• Drainage system should fulfill 2 criteria:-
• Have maintained permeability
 by providing relatively unimpeded flow of water
• Filtration of base soil
 by preventing the migration of soil fines into the drain

33. CONCLUSION
 Geotextiles are an efficient effective and economic method of solving
most of the geotechnical problems in roads.
 The design engineer should be well aware of the possible problems
and should use this relatively new tool for solving them.
 For this he/she should understand properties and capabilities of the
geotextile material.

34. THANK YOU
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