A geotextile is defined as any permeable textile material that is used with foundation, soil, rock, earth, etc to increase stability and decrease wind and water erosion.
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).
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.
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%
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
26.
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
30.
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
32.
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.