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SEMINAR ON
Overview of The
Presentation Scope of geo-synthetics
What are geo-synthetics
Types of geo-synthetics
Geo-synthetic Advantages
Functions
Sub-grade conditions in which geosynthetics are useful
Potential geo-synthetic benefits
Conclusions
2 Geo-synthetic Reinforced Pavements
SCOPE OF GEO-
SYNTHETICS
Limited financial resources
Requirement of high- quality materials
Unavailability or short in supply
3 Geo-synthetic Reinforced Pavements
WHAT ARE GEO-
SYNTHETICS..?
A range of generally synthetic products
used to solve geotechnical problems.
The synthetic nature make them suitable
for use in the ground where high levels
of durability are required
Geo-synthetic Reinforced Pavements 4
WHAT ARE GEO-
SYNTHETICS..?
ASTM (1997) has defined a geo-
synthetic as a planar product
manufactured from a polymeric material
used with soil, rock, earth, or other
geotechnical-related material as an
integral part of a civil engineering
project, structure, or system.
5 Geo-synthetic Reinforced Pavements
TYPES OF GEO-SYNTHETICS
The term is generally regarded to
encompass four main products,
Geo-textiles
Geo-nets/geo-grids
Geo-membranes
Geo-composites
Geo-synthetic Reinforced Pavements 6
Geo-textiles
Manufactured from mainly polymeric yarns
and fibers, consisting primarily of
polypropylene, polyester, polyethylene and
polyamide
Woven - interlacing of yarns
Non-woven - by various methods other than
weaving, mainly heat bonded, needle
punched and chemically bonded
Geo-synthetic Reinforced Pavements 7
Geo-synthetic Reinforced Pavements 8
Geo-nets/geo-grids
Stiffer than geo-textiles and have relatively
large voids within the material
Production include bonding or interlacing.
Produced from nearly all polymeric
materials.
Geo-synthetic Reinforced Pavements 9
Geo-nets/geo-grids
Geogrids are meshes of a regular pattern
of tensile elements usually made of a
fairly rigid type of plastic
They provide increased shear strength
between soil strata interfaces
Geo-synthetic Reinforced Pavements 10
Geo-synthetic Reinforced Pavements 11
Geo-membranes
Impermeable sheets produced from
polymeric materials
Manufactured several ways, excluding
woven methods
Manufactured using fiberglass and
bitumen
Geo-synthetic Reinforced Pavements 12
Used widely as cut-offs and liners
Applied largely is the containment of
hazardous and municipal wastes and their
leachates
Acts as an escape route for gases and
leachates generated in wastes
Geo-synthetic Reinforced Pavements 13
Made of various materials including low
density polyethylene, high density
polyethylene, polyvinyl chloride and
polypropylene
PVC geo-membranes are very flexible and
can conform to uneven surfaces without
being punctured
Geo-synthetic Reinforced Pavements 14
Geo-synthetic Reinforced Pavements 15
Geo-composites
Geosynthetics which are
a combination of any of the above three
A geo-net sandwiched between two non-woven geo-textile layers can be used to provide a drainage layer with high transmissivity
Geo-synthetic Reinforced Pavements 16
Geo-synthetic Reinforced Pavements 17
GEO-SYNTHETIC
ADVANTAGES Space Savings
Material Quality Control
Construction Quality Control
Cost Savings
Technical Superiority
Construction Timing
Material Availability
Environmental Sensitivity
Geo-synthetic Reinforced Pavements 18
FUNCTIONS 1. Separation
2. Filtration, drainage
3. Reinforcement
4. Fluid Barrier
5. Protection
Geo-synthetic Reinforced Pavements 19
Bearing capacity
increase
Membrane tension
support
Lateral restraint
Separation
Geo-synthetic Reinforced Pavements 20
Geo-synthetics is placed at the interface
between the aggregate base course and
the sub-grade.
Functions as a separator to prevent two
dissimilar materials (sub-grade soil and
aggregates) from intermixing.
Separation
Geo-synthetic Reinforced Pavements 21
Filtration, Drainage
Geo-textile act as a filter to prevent fines
from migrating up in to the aggregate
due to high pore water pressures
Acts as a drain, allowing the excess
pore water pressures to dissipate
through the geo-textiles
Geo-synthetic Reinforced Pavements 22
Reinforcement
Improves the performance of pavements by three possible mechanisms
1. Lateral restraint
2. Bearing capacity increase
3. Membrane tension support
Geo-synthetic Reinforced Pavements 23
Lateral Restraint
Lateral restraint of the base and sub-grade
through friction and interlock between the
aggregate, soil and the geo-synthetic
Geo-synthetic Reinforced Pavements 24
Lateral Restraint
Geo-synthetic Reinforced Pavements 25
Bearing Capacity Increase
Increase in the system BP by forcing the
potential BP failure surface to develop along
alternate, higher shear strength surfaces.
Geo-synthetic Reinforced Pavements 26
Bearing Capacity Increase
Geo-synthetic Reinforced Pavements 27
Membrane Tension
Support
A third possible geo-synthetic reinforcement
function is membrane-type support of wheel
loads
Geo-synthetic Reinforced Pavements 28
Membrane Tension Support
Geo-synthetic Reinforced Pavements 29
Fluid Barrier
Geo-membranes, thin-film geo-textile
composites, are used as fluid barriers to
impede the flow of a liquid or gas one
location to another.
Geo-synthetic Reinforced Pavements 30
Protection
The geo-synthetic acts as a stress relief
layer.
Geo-synthetic blankets and geo-synthetic
mats reduce erosion caused by rainfall
impact.
Nonwoven geo-textiles is often used to
prevent puncture of geo-membranes (by
reducing point stresses)
Geo-synthetic Reinforced Pavements 31
FUNCTIONS
Geo-synthetic Reinforced Pavements 32
FUNCTIONS
Geo-synthetic Reinforced Pavements 33
SUBGRADE CONDITIONS IN
WHICH GEO-SYNTHETICS
ARE
USEFUL
Poor soils
(SC, CL, CH, ML, MH, OL, OH, and PT)
Low un-drained shear strength
Cu < 90 kPa
CBR < 3
Geo-synthetic Reinforced Pavements 34
SUBGRADE CONDITIONS IN
WHICH GEO-SYNTHETICS
ARE
USEFUL
High water table
High sensitivity
Under these conditions, geosynthetics function primarily as separators and filters to stabilize the sub-grade.
Geo-synthetic Reinforced Pavements 35
FUNCTIONS
Un drained Shear
Strength (kPa)
Sub-grade CBR
Functions
60 – 90
2 - 3
Filtration and possibly
separation
30 - 60
1 - 2
Filtration, separation,
and
possibly reinforcement
< 30
< 1
All functions, including
reinforcement
Geo-synthetic Reinforced Pavements 36
POTENTIAL GEO-
SYNTHETIC BENEFITS
Reduces the intensity of stress on the sub-
grade and prevents the base aggregate from
penetrating in to the sub-grade. (Function:
separation).
Prevents sub-grade fines from pumping or
otherwise migrating up in to the base.
(Function: separation and filtration).
Geo-synthetic Reinforced Pavements 37
Prevents contamination of the base materials.
(Function: filtration).
Reduces the thickness of aggregate required to
stabilize the sub-grade. (Function: separation
and reinforcement).
Reduces disturbance of the sub-grade during
construction. (Function: separation and
reinforcement).
Geo-synthetic Reinforced Pavements 38
Allows an increase in sub-grade strength
over time. (Function: filtration).
Reduces the differential settlement of the
roadway, this helps in maintain pavement
integrity and uniformity. (Function:
reinforcement).
Geo-synthetic Reinforced Pavements 39
Reduces the depth of excavation required
for the removal of unsuitable sub-grade
materials (Function: separation and
reinforcement).
Reduces maintenance and extends the life
of the pavement. (Functions: all).
Geo-synthetic Reinforced Pavements 40
CONCLUSIONS
Geo-synthetic reinforcement in pavement
design and construction should be
widespread.
Geo-synthetic reinforcements are
incorporated into permanent, paved roads
either as base (or sub-base) reinforcement
As sub-grade restraint for construction of
flexible or rigid roadways over weak sub-
grade conditions
Geo-synthetic Reinforced Pavements 41
REFERANCES
1. Engineering properties of sand fiber mixtures
for road construction by Rosa L. et al, Journal
of geotechnical and geo-environmental engg.
March 2001
2. Performance of geo-synthetic reinforced
asphalt pavements by Hoe I Ling et al, Journal
of geotechnical and geo-environmental engg.
February 2001
Geo-synthetic Reinforced Pavements 42
3. Geo-synthetic reinforcement of aggregate
base/sub-base courses of pavement
structures GMA White paper II June 27, 2000
4. Experimental analysis of geo-textiles & geo-
fibers composites, by Dr A. K. Haghi
Geo-synthetic Reinforced Pavements 43
Geo-synthetic Reinforced Pavements 44