GEO-SYNTHETICS MEANS GEO-EARTH AND SYNTHETICS-MAN MADE. AKASH V. MODI MERCHANT ENGINEERING COLLEGE, BASNA CIVIL DEPARTMENT

1. Prepared by:
AKASH V. MODI
Asst. Prof.
Civil Engg. Dept.
Merchant Engineering College, Basna

2.  The word GEO refers to an end use associated
with improving the performance of civil
engineering works involving earth/ground/soil.
 The word SYNTHETICS refers to fact that the
materials are almost Manmade.
 The materials used in the manufacture of
Geosynthetics are primarily synthetic polymers
generally derived from crude petroleum oils,
rubber, fibre glass and other materials are also
sometimes used.

3. Geosynthetics are fabric like material made
from polymers such as polypropylene,
polyethylene, polyester, polyvinyl chloride
(PVC), nylon etc.
The term Geosynthetics include following:
1. Geotextiles
2. Geogrids
3. Geomembranes
4. Geonets
5. Geocomposites

4. Each type of Geosynthetics perform one or
more of following major functions:
1. Reinforcement
2. Separation
3. Filtration
4. Drainage
5. Fluid barrier
6. Protection

5. Geotextiles
Woven
Monofilament Multifilament
Tape
threaded
Non-woven
Mechanical
bonded (Needle
punched)
Chemical bonded
(Resins)
Thermal
bonded
(Heat
treated)

7. Geotextiles are planer, permeable, polymeric
textile products in the form of flexible sheets.
Main functions of geotextiles are:
1. Reinforcement
2. Separation
3. Filtration
4. Drainage
5. Erosion control
6. Fluid barrier
7. Protection

8. 1. REINFORCEMENT:
 A Geosynthetic performs the reinforcement function by
improving mechanical properties of a soil mass as a result
of its inclusion.
 When soil and geosynthetic reinforcement are combined, a
composite material, reinforced earth is produced that
possesses high compressive and tensile strength.
 The geosynthetic acts as a tensioned member coupled to
the soil material by friction, adhesion, interlocking or
confinement and thus maintains stability of soil mass.
 It can be divided into two categories.
1. A tension member which supports a planar load
2. A tension member which supports a planar load as well as
normal load.

9. 1. REINFORCEMENT:

10. 2. SEPARATION:
 A geotextile acts as a separator when placed
between a fine soil and a coarse material such
as gravel or stone ballast.
 It prevents fine soil and coarse material from
inter-mixing under action of repeated applied
loads.

11. 2. SEPARATION:

12. 3. FILTRATION:
 A geosynthetic acts as a filter when it allows liquid to
pass normal to its own plane while preventing most
soil particles from being carried away by liquid
current.
 A geosynthetic allowing passage of water from a soil
mass while preventing migration of soil particles.
 Two cases may be considered:
1. A geotextile placed across a flow of liquid carrying
fine soil particles, stops most of particles.
2. A geotextile placed in contact with a soil, allows water
seeping from soil to pass through, while preventing
any movement of soil particles.

13. 3. FILTRATION:

14. 4. DRAINAGE:
 If geotextile provides fluid transmission
within its own plane towards an outlet, it is
said to perform the function of drainage.
 Drainage is related to role of filtration and is a
function of permeability of a geotextile and
its pore opening size or porometry.

15. 4. DRAINAGE:

16. 5. FLUID BARRIER:
 A geosynthetic also perform fluid barrier
function, if it acts like an almost impermeable
membrane to prevent passage of liquids or
gases.
 A layer installed at base of a pond, prevents
the infiltration of liquid waste in to the natural
soil.

17. 5. FLUID BARRIER:

18. 6. PROTECTION:
 A geosynthetic placed between two materials
performs protection function when it alleviates or
distributes stresses and strains transmitted to
material to be protected against any damage.

19.  These are planar, polymeric products consisting of mesh
or net like regular open network of intersecting tensile
resisting elements, called ribs, integrally connected at
junctions.
 The ribs can be linked by extrusion, bonding or
interlacing : resulting geogrids are extruded geogrid,
bonded geogrid and woven geogrids.
 Extruded geogrids are classified as
1. Unaxial geogrid
2. Biaxial geogrid
 The main function of geogrids is an reinforcement.

21.  These are planar, impermeable, synthetic sheets
manufactured from materials of low permeability to
control fluid migration in a project as a barrier or liner.
 These include HDPE, PVC, PP liners etc. and are
basically impervious.
 Many scrim-reinforced geomembranes manufactured in
single piles have thickness that range from 0.25 to about
0.4 mm.
 The main function of geomembranes is liquid barrier or
liner.
 The most important aspect of construction with
geomembranes is preparation of seams (joints).

22.  Following tests should be conducted on geomembranes
when they are to be used as landfill liners:
1. Density
2. Mass per unit area
3. Water vapour transmission capacity
4. Tensile behaviour
5. Tear resistance
6. Impact resistance
7. Puncture resistance
8. Chemical resistance
9. UV resistance
10. Stress cracking

24.  These are planar, polymeric products consisting of
regular dense network of integrally connected parallel
sets of ribs overlying similar sets at various angles.
 These include HDPE and LDPE nets and have
functions similar to geogrids.
 The geonets are mainly used as reinforcements.

25.  These are made by bonding together geomembranes and
geotextiles with some other materials for specific applications
in drainage, erosion control, bank protection etc.
 Two or more materials may be combined of which atleast one
is a geosynthetic of some types.
 Various geotextile related products are:
1. Geocell
2. Geofoam
3. Geomat
4. Geomesh
5. Geopipe
6. Geospacer

27. 1. GEOCELL:
 A three dimensional, permeable, polymeric honeycomb or
web structure, assembled from geogrids and special bodkin
couplings in triangular or square cells.
2. GEOFOAM:
 A polymeric material manufactured by application of
polymer in semi-liquid form through use of a foaming agent
to have a light weight material in slab or block form with
high void content for as lightweight fills, thermal insulators
and drainage channels.
3. GEOMAT:
 A three dimensional polymeric structure and permeable made
of coarse and rigid filaments bonded at their junctions used to
reinforce roots of vegetation and to extend erosion control.

28. 4. GEOMESH:
 A geosynthetic with a planar woven structure
having large pore sizes, which vary from several
mm to several cm for use in mainly erosion
control works.
5. GEOPIPE:
 A plastic pipe placed beneath the ground surface
and subsequently backfilled.
6. GEOSPACER:
 A three dimensional polymeric moulded
structure consisting of cuspidated or corrugated
plates with large voids.

29.  Geosynthetics are widely used in the field of civil
engineering. The major application areas are:
1. Retaining walls
2. Embankments
3. Shallow foundation
4. Railway tracks
5. Roads
6. Slopes
7. Filters and drains
8. Tunnels
9. Earthen dams

30. 1. RETAINING WALLS:
 Geosynthetic reinforced retaining walls consist
of Geosynthetic layers as reinforcing elements in
backfill to help resist lateral earth pressure.
 A Geosynthetic reinforced retaining wall has
basic three components:
1. Backfill – usually specified to be granular soil.
2. Reinforcement layers – geotextile or geogrids.
3. Facing element – generally used to maintain
appearance and to avoid soil erosion.
 Geotextile is also used in retaining walls to
perform drainage function.

31. 1. RETAINING WALLS:

32. 2. EMBANKMENTS:
 The geosynthetic as the basal layer in the
embankment over soft foundation soil can
serve one of the following basic function or
combination of these.
1. Reinforcement
2. Drainage
3. Seperation/filtration

33. 2. EMBANKMENTS:

34. 3. SHALLOW FOUNDATION:
 it may be provided below shallow footings to
improve bearing capacity of soils.
 Also it can be provided to support footing of
many structures including warehouses, oil
drilling platform, parking areas, etc.

35. 4. ROADS:
 Geotextiles in subgrade – subbase interface of
a road can effectively deal with same.
 Provision of geotextiles in road works may
serve three functions:
1. Separation
2. Drainage
3. reinforcement

36. 4. ROADS:

37. 5. RAILWAY TRACKS:
 Geosynthetics is used for track stabilization in
USA, Canada, Europe.
 Geotextiles are used in high performance
locations such as turnouts, rail crossings,
switches and highway crossings.
 Main functions of geotextile when used in
track structure:
1. Separation
2. Filtration
3. Lateral drainage

38. 6. FILTERS AND DRAINS:
 In filters, geotextile is in conjunction with
granular materials or pipes.
 In drainage applications, it prevents upstream
soils from entering adjacent granular layers of
subsurface drains.

39. 6. FILTERS AND DRAINS:

40. 7. SLOPES:
 Geotextile on a bare slope decreases water
runoff velocity until seed germination can
occur and control erosion of soil.
 Geotextile can be used to prevent erosion of
slopes of earthen dams, river banks and
canals.

41. 7. SLOPES:

42. 8. EARTHEN DAMS:
 Geotextiles can be effectively used as filter
media in erosion control of earthen dam
slopes.
 Functions of geotextiles are:
1. Erosion control or slope protection
2. Filtration and drainage material for seepage
control
3. Filtration and separation function
4. Filter wraps around PVC perforated pipes.

43. 9. TUNNELS:
 Geotextiles and geomembranes are
commonly used in modern day tunnel
technology to construct waterproof tunnels.
 The non-woven geotextile acts as a drainage
layer and as protection for waterproofing
geomembrane.

44. 9. TUNNELS: