This Presentation deals with latest Ground improvement Techniques for various civil engineering projects like highway construction etc. and river side protection techniques.
2. INTRODUCTION :-
Ground improvement is the most imaginative
field of the geotechnical engineering. It is the field
in which the engineer forces the ground to adopt
the project requirements by altering its natural
state , instead of alter in design.
The result usually include saving in construction
cost and reduction of implementation time
3. NEED TO IMPROVE GROUND..
To reduce settlement of structure
Improve shear strength of soil and thus
increasing bearing capacity of soil
Increase the factor of safety against possible
failure of embankment.
Reduce the shrinkage and swelling of soils
Increase the liquefaction resistance
4. SIMPLE METHOD TO DESCRIBE
GROUND IMPROVEMENT
Drop a handful of sand from certain height. You
will get a heap of sand. Keep your foot over it,
sand will disperse in all directions. Measure this
dispersion as ‘x’
Drop again handful of sand on the leap of sand .
Keep your handkerchief on the top and then keep
your foot . Dispersion of sand will again be there ,
but less than previous one.
Reason :- Friction developed between
handkerchief and soil due to which adhesion took
place between cloth and soil particles, thus soil
did not flow away
5. Research in the use of
Geosynthetic product
Geosynthetics like geotextiles, geogrid,
geomembrane can lead to less deformation and
high strength to road and can reduce thickness of
the pavement
Functions Geotextile Geogrids Geomembrane Geocompos
its
separation √ - - -
filtration √ - - √
reinforcement √ √ - -
Drainage √ - - √
Erosion control √ - - -
Slope
protection
√ - √ -
6. Geogrids
Geogrid are integrally polymer meshes. The
meshes are made of high tensile polymer
(HDPE/PP) and are totally on biodegradable and
anticorrosive. They have fused or thermally
welded joints having high dimensional stability
and strength. These grids are immune from
naturally occurring soil alkalies,acids and mineral
salts
12. Vegetation Structure- Fascines
Bundles of cuttings tied together, placed in
shallow trenches parallel to the bank
Partially buried and staked in place
Creates log-like structure that will quickly root,
grow and provide plant cover
Holds soil in place to protect stream bank from
erosion
15. Sacks
Filled with soil or sand-cement mixture
Primarily used for emergency work during floods
Protects stream banks when proper riprap isn’t
available
Advantages compared to stone riprap
Allow placement on steep slopes
Use locally available materials
Creates smooth boundary
Cobblestone effect may be more aesthetic
16. Sacks and Blocks
Blocks
Sacks
-Manufactured with local materials or obtained
commercially Cast with openings to provide for
drainage
-Openings also allow vegetation to grow so
that the root structure can strengthen the bank
-Can be used with a filter if erosion is a
concern
Advantages
-Durable, less susceptible to freeze/thaw
-Easy pedestrian access to river
-Low channel boundary roughness
18. About Gabions
Rectangular wire boxes (baskets) filled with
small-sized stones
Used where flow velocities are too high for riprap
of small stones
Made of heavy galvanized steel with PVC coating
for corrosive environments
Stacked on relatively steep slopes to resist river
flows and unstable banks
Need to be periodically inspected and maintained
from damage
19. Mattress Gabions
Shaped into shallow, broad baskets tied together
side by side to form continuous blanket of
protection
Placed on a smoothly graded riverbank slope
May still allow some natural vegetation growth
20. Comparison between geogrid
reinforced section & unreinforced
section
Unreinforced
Reinforced
40 mm — Bituminous concrete — 40
mm
75 mm — Dense bituminous concrete — 55
mm
250 mm — Granular base(WBM) — 200
mm
250 mm — Granular sub base —
235 mm
21. PROPERTIES COMMON TO
GEOTEXTILES
Good resistance to chemicals
Resistance to biological degradation
Thermal stability 0 to 120˚c
Material – 100% polypropylene
Specific gravity- 0.91
Weight/sq m-206-303gm/m
Thickness-0.58-0.78
Tear strength- wrap way-21-69kg
-weft way-18-71kg
Breaking strength- wrap way-245-500kg
- weft way-181-333kg