Presentation prepared for the course 'Soil Mechanics' in Civil Engineering

1. Soil Compaction: A case
study of Anpara Thermal
Power Plant, Uttar Pradesh
By: JATIN DAYMA (2013UCE1448)
NITIN KUMAR GUPTA (2013UCE1458)
NITIN KUMAR (2013UCE1333)
MANISH Kumar (2013UCE1299)
RAMESH Kr. BAGARIYA (2013UCE1273)

2. What is compaction?
Compactive
Effort
+ water =

3. Objectives of Compaction
• To provide man-made ground to support a structure
• As a sub-base for a road, railway or airfield runway.
• As a structure in itself, such as an embankment or
• To refill an excavation, or a void adjacent to a
structure
(such as behind a retaining wall.)
earth dam, including reinforced earth

4. Soil
Matrix
Three phases of soil under
compaction

5. Compaction Curve

6. What happens to the relative quantities of three
phases with addition of water?

7. Factors Influencing Compaction
Characteristics of Soils
•Type of soil
•Compactive effort
•Effect of soil Structure / water Content
•Organic content

8. Water Content
Dry Density
Effect of Energy on Soil Compaction
Higher
Energy
ZAV
Increasing compaction energy Lower OMC and higher dry density
In the field
increasing compaction energy =
increasing number of passes or
reducing lift depth
In the lab
increasing compaction energy
= increasing number of blows

9. Different methods of
Field Compaction

10. Smooth Wheel Roller
Provide a smooth finished grade
Used for paving
Effective only upto 20-30 cm,
[Therefore place the soil in shallow layers (Lifts)]

11. Sheepsfoot roller :
Greater compaction pressure,Provides kneading action,
“walk out” after compaction
Effective for compacting fine-grained soil / Clays

12. Pneumatic roller
Effective for compacting clayey soil and silty soils

13. Vibratory roller/Plate
 Effective for granular soil

14. Impact Roller
Provides deeper compaction (2-3 m) eg. Air fields

15. Deep Compaction-Dynamic
compaction
Pounder (Tamper)
Crater created by the impact
(to be backfilled)
Suitable for granular soils, land fills
and karst terrain with sink holes.
(Solution cavities in lime stone)

16. Dynamic compaction
Pounder (Tamper)
Mass = 5-30 ton
Drop = 10-30 m

17. Dynamic compaction

18. Vibroflotation
Suitable for granular soils
Practiced in several forms:
 vibro–compaction
 stone columns
 vibro-replacement
Vibroflot (vibrating unit)
Length = 2 – 3 m
Diameter = 0.3 – 0.5 m
Mass = 2 tonnes
(lowered into the ground and vibrated)

19. Case Study
Ground Improvement of an Existing Ash Pond
Site: Anpara Thermal Power Plant, Uttar
Pradesh
Objective: Expansion of existing thermal
power plant
Site allocated for Expansion: An abandoned
Ash Pond of
area app. 5400
acres.
(Unit D of 2x500) MW Capacity

20. Anpara Thermal Power Plant

21. SATELLITE VIEW OF SITE-

23. There are three types of ash produced by thermal
power plants-
Fly ash- Fly ash is collected by mechanical or electrostatic precipitators
from the flue gases of power plant.
Bottom ash- Bottom ash is collected from the bottom of the boilers.
Pond ash- When Fly ash and Bottom ash are mixed together,
are transported in the form of slurry and stored in the lagoons, the deposit
is called pond ash.
In this case, we are concerned with the pond ash
only.

24. Initial Soil Condition of Site-
Soil Strata:
Ash deposit 3-13m
Clayey silt/Silty clay up to 23m
Dense sandy silt or Hard clayey silt with occasionally
weathered rock (Granitic gneiss)
State of Denseness: Loose to Medium dense in
condition
Existing bearing capacity of the fly ash deposit: < 10
t/m2

25. Fly ash
Clay

26.  SPT value of Ash deposit- Range of N 2 to 30, but
on an average 3 to 8 (penetration value)
 Site falls under Zone III – IS 1893 (Part1) 1982-
Susceptible liquefaction
 Method adopted for improvement of the Ash
Pond: Vibro Stone Column (Dry bottom feed
method)

27. Vibro Stone Columns (VSCs) offer a highly
economical and sustainable alternative to piling and deep foundation
solutions; removing the need to by-pass problem ground by densifying and
strengthening weak or poorly compacted soils in-situ.
Bottom Feed Method- Where a high water table or weak
soils are present the collapse of the bore hole is much more likely when
the vibroflot is withdrawn. In these conditions the purpose built Bottom
Feed system is used to ensure integrity of the stone column from top to
bottom. The vibro rig is fitted with a hopper which feeds stone into a tremie
pipe running down the length of the vibroflot.

28. Ground Improvement Technique
Vibro Stone Column (Bottom feed method):
Rig used: Vibrocat, opeMethod does not require water for
penetration thus avoiding
the disposal of large quantities of muck and also making
environmental friendly
rational advantage is it is able to exert
a pull down force improving penetration speed

29. videoplayback.mp4

30. Method-
 Vibrocat feeds the Coarse granular material to the
tip of vibrator with the aid of pressurized air
 Installation method consists of alternate step of
penetration and retraction
 During retraction gravel runs into the annular space
created and then compacted using vibrator thrusts and
compressed air

31. Vibroflotation
Suitable for granular soils
Practiced in several forms:
 vibro–compaction
 stone columns
 vibro-replacement
Vibroflot (vibrating unit)
Length = 2 – 3 m
Diameter = 0.3 – 0.5 m
Mass = 2 tonnes
(lowered into the ground and vibrated)

32. Stone Column
vibrator makes a
hole in the weak
ground
hole backfilled ..and compacted Densely
compacted
stone column

33. Why vibro stone columns
method?
 Improve Bearing Capacity of Open
Foundations (10 T/m2
)
 Enhance Lateral Capacity of Piles (7 T)
 Mitigate Liquefaction Potential

34. Improving Bearing Capacity of
open foundation
Vibro stone column of dia 0.9m at 2m
centre to centre spacing in a
triangular grid pattern resulted the
bearing capacity value 10 T/m2

35. Result of plate load test

36. Improving lateral load
capacity of piles
Vibro stone columns are installed
at specified pattern surrounding
the BCIS piles to enhance the
density of fly ash deposits which
in turn can improve the lateral
load carrying capacity.

37. Vibro stone columns installed at
specified pattern surrounding the bored
cast-in-situ piles

38. Result of lateral load test

39. After Improvement, Result Reported
After Improvement, Result Reported:
Design lateral load capacity = 7 T
Ultimate Load = 20 T

40. EXECUTION OF MAIN
WORK

41. 34,000 m of vibro stone columns
0.9m dia are installed for open
foundations of various structures like
pump house, cable gallery,
drive house etc at coal
handling plant.

42. Open Foundation of Pump
House structure

43. Similarly, to enhance the lateral load
carrying capacity of BCIS piles of
structures like conveyor, crusher
house etc of coal handling plant,
45,000 m of 0.5m diameter vibro
stone columns are installed.

44. Typical detail of stone column installed
surrounding the piles

45. Conclusion
• The unit built on the fly ash pond - the
first of its kind in the country
• No fresh land acquisition
• Utilisation of dumping site