This document provides information on field compaction techniques and procedures. It discusses the commonly used ground improvement technique of soil compaction through external effort to reduce air volume. It describes field compaction methods using rollers, tampers, vibratory probes and blasting. Case studies are presented on using vibro-stone columns to improve bearing capacity of ash pond for construction of a power plant. Procedures for relating field and laboratory compaction test results are also summarized.

1. Jagadanand Jha
Guru Nanak Dev Engineering College, Ludhiana
141006, India
&
Sanjay Kumar Shukla
Edith Cowan University, Perth, WA 6027, Australia

2. Compaction
Laboratory Test
Field Compaction
Case Study
Derivation for Field Compaction

3. The most commonly used ground improvement technique,
where the soil is densified through external compactive
effort/mechanical means by reducing volume of air.
Compactive
Effort
+ water =

4. •To refill an excavation, or a void adjacent to a structure
(such as behind a retaining wall.)
•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 earth dam,
including reinforced earth
Improvement Effect on mass fill
Higher shear strength Greater stability
Lower compressibility Less settlement under state load
Higher CBR value Less deformation under repeated
Lower permeability Less tendency to absorb water
Lower frost susceptibility Less likelihood of frost heave

5. Zero Air
Compaction Curve Void Curve
Sr =100%
ρ d, max
Load
optimum water content
Air Air
water Water
Soil Compressed Soil
Matrix
Solid Solid
Vol. = VT2
Vol. = VT1
γsoil (2) > γsoil (1)

6. Soil Compaction in the
Lab:
1- Standard Proctor Test
2- Modified Proctor Test
3- Gyratory Compaction
Standard Proctor Test
Modified Proctor Test

8. Gs γw
Soil Compaction in the Lab: γZAV =
Gs γ w 1+ Wc Gs
1- Standard Proctor Test γ dry = Sr
1+ e Dry Density
Zero Air Void Curve
Sr =100%
5.5 pound hammer
γ d max
3
H = 12 in
4
2
5
1
25 blows
per layer
Compaction
wc1 wc2 wc3 wc4 wc5 Dry to Wet to
Optimum Optimum
Curve
γd1 γd2 γd3 γd4 γd5 (OWC) Water
Content
Optimum
Increasing Water Content Water
Content
γwet
4 inch diameter compaction mold. γdry =
1+ Wc%
(V = 1/30 of a cubic foot)
100

10. Soil Compaction in the Lab:
Zero Air Void Curve
Sr = 60%
Dry Density
1- Standard Proctor Test Zero Air Void Curve
Sr =100%
ASTM D-698 or AASHTO T-99
γ d max
Energy = 12,375 foot-pounds per cubic foot
Zero Air Void Curve
γ d max
Sr < 100%
Compaction
Curve for
2- Modified Proctor Test Modified
ASTM D-1557 or AASHTO T-180 Proctor
Energy = 56,520 foot-pounds per cubic foot
Compaction
Curve for Standard
Proctor
(OMC) Moisture
(OMC)
Content
Number of blows per layer x Number of layers x Weight of hammer x Height of drop hammer
Energy =
Volume of mold

11. •Type of soil
•Compactive effort
•Effect of soil Structure / water Content
•Organic content

12. Type of clay
Effect of clay content
on density (Das 2006)
Proctor compaction test on
Sand

13. Effect of Energy on Soil Compactio (Compactive Effort)
Increasing compaction energy Lower OWC and higher dry density
Higher
Dry Density
Energy
In the field
increasing compaction energy
ZA
= increasing number of passes
V
or reducing lift depth
In the lab
increasing compaction energy
= increasing number of blows
Water Content

15.  Dry side of
optimum-
Flocculated
structure and wet
side of optimum-
Dispersed structure
 Higher compactive
effort or water
content give more
dispersed fabric

16.  Cohesive Soil:
 Attractive force -Van der waals
force acts between two soil
particles; Remains same in
magnitude
 Repulsive force – Due to the
double layer of adsorbed water
tending to come into contact
with each other; directly related
to the size of double layers
 If net force is attractive –
Structure is Flocculated
 If net force is repulsive –
Structure is Dispersed

17.  Low Water Content:
 Repulsive force is
small because double
layer is not fully
developed; net force is
attractive.
 Makes difficult for
particle to move when
compactive effort is
applied: Result low
dry unit weight

18.  High Water Content:
 Interparticle repulsive
force increases since
double layer expands
 Particle easily slide
over one another and
get packed more
easily : Result high
dry unit weight

19.  Double layer expansion
is complete at Optimum
Moisture Content
(OMC): Result
maximum dry unit
weight at this stage
 Beyond OMC; water
does not add to
expansion but replaces
the soil grains by water:
Result a decrease in dry
unit weight

20.  First Decrease in dry
unit weight with
increase in water
content
 Reason:Capillary
tension in pore water
prevents soil particle
coming close together
(Phenomenon- Bulking
of Sand- maximum
bulkking occurs at 4-5%
water content)
 Further increase in
water content : Menisci
are broken and particles
move and adopt to a
closer packing

21. Permeabilty higher
when compacted dry
of optimum than when
compacted wet of
optimum

22. At relatively low stress level
clays compacted wet of
optimum are more
compressible
At relatively high stress level
clays compacted dry of
optimum are more
compressible

23. Organic content
Effect of drying history and
Maximum dry unit weight Vs. organic content on optimum
Organic content for all compaction moisture
test content (Das 2006)
(Das 2006)

24. Shallow Compaction: Compaction depends on
following factors
Thickness of lift
Area over which the pressure is applied
Intensity of pressure applied to the soil
Type of roller
Number of roller passes
Effect of number of passes on
compaction of lean clay

25. 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)]

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

27. Effective for compacting clayey soil and silty soils

28. Effective for granular
soil

29. Compacted unit weight for 8ft (2.44m)
lift height for 2,5,15 and 45 vibratory
roller passes

30. Provides deeper compaction (2-3 m) eg. Air fields

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

32. Pounder (Tamper)
Mass = 5-30 tonne
Drop = 10-30 m

34. 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)

41. vibrator makes a hole backfilled ..and compacted Densely
hole in the weak compacted
ground stone column

42. For densifying granular soils
Aftermath of blasting
Fireworks

43. Site: Anpara Thermal Power Plant, Uttar Pradesh
Expansion of existing thermal power plant:Unit D of 2x 500
MW Capacity
Site allocated for Expansion: An abandoned Ash Pond of
area app. 5400 acres.
Depth of Site: 3m to 13m
State of Denseness: Loose to Medium dense in condition
Existing bearing capacity of the flyash deposit: < 10 t/m2
Site falls under Zone III – IS 1893 (Part1) 1982-
Susceptible to liquefaction
Method adopted for improvement of the Ash Pond:
Vibro Stone Column (Dry bottom feed method)

44. Soil Strata:
Ash deposit 3-13m
Clayey silt/Silty clay upto 23m
Dense sandy silt or Hard clayey silt with
occasionally weathered rock (Granitic gnesis)
 Density within Ash deposit:
Considerable variation
SPT value of Ash deposit –
Range of N 2 to 30, but on an average 3 to 8
SPT value of Hard Clayey Silt :
N ranges between 9 and 30

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

47. 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
10t/m2

48. Vibro stone column enhanced the density
of Fly ash deposits, which inturn improved
Lateral load carrying capacity.
After Improvement, Result Reported:
Design lateral load capacity = 7 t
Ultimate Load = 20 t

50. Typical detail of stone column installed surrounding the piles

51.  The selection of right depth, right diameter and
proper compaction is essential.
 Computerised monitoring of penetration depth
of vibrator.
 Sensor within the depth vibrator indicates the
compaction effort of depth vibrator.

52.  General Procedure in Compaction Tests
 Depending on the size of the compaction mould, a
fraction of the soil sample having particle size
larger than a specific value, say d0, is discarded
 For example, in the standard Proctor compaction test,
the soil particles coarser than 19 mm are discarded
before compacting soil in the standard 101.6 mm-
diameter laboratory mould; IS270 (Parts 7 and 8)
recommends 100-mm diameter mould (BIS, 1980,
1983); AS1289.5.1.1 (Standards Australia, 2003)
recommends 105-mm diameter mould

53.  If the fraction removed is significant, the
laboratory optimum moisture content and the
maximum dry unit weight determined for the
remaining soil are not directly comparable with
the field values.
 To make laboratory values more representative,
the following approaches can be used:

54.  In the laboratory soil sample for conducting the
test, the coarse fraction larger than d0, say 19
mm, is replaced by an equal amount of
material between 19 mm and the next smaller
sieve size, say 4.75 mm;
 The water/moisture content and dry unit
weight of the discarded coarse fraction (larger
than d0) are estimated and the field values are
computed as weighted averages of those of the
discarded coarse fraction and of the remaining
soil.

55.  The field optimum moisture
content is calculated using
water content of coarse Zero Air
fraction (larger than d0) as Void Curve
described above in second Sr =100%
approach, and then the
maximum dry unit weight is
calculated assuming that the ρ d, max
saturation of the soil in field
is equal to that achieved in
the laboratory test. This
treatment is equivalent to
shifting the compaction
curve upward along a
saturation line. It requires optimum water content
knowledge of the specific
gravity of the soil particles.

56. First step:
To calculate the saturation
from the laboratory values of Zero Air Void
maximum dry unit weight, Curve
optimum moisture content Sr =100%
and specific gravity of soil
particles.
ρ d, max
Second step:
The equivalent field unit
weight is then computed
from the laboratory degree
of saturation, field optimum
moisture content and specific optimum water content
gravity of soil particles.

58. Field Compacted Sample Laboratory Compacted Sample
When the coarser fraction, larger than size d0 (e.g. 19 mm), is removed, it
also takes away some water associated with its water content.
In addition, there is also possibility of some change in the air void volume
when the soil is compacted without this coarse fraction.

59.  1/γdF=(1-p)(1+β)/γdL+p/Gcγw+(pWc-(1-p)βWL)/γw-(1-p)β/(Gfγw)
 WF = (1-p)WL+pWc
 Gf = specific gravity of the fine soil particles (smaller than d0) in the field/laboratory soil
sample
 Va = volume of the air in voids of the field soil sample
 VF = total volume of field soil sample
 VL = total volume of the laboratory soil sample
 wc = water content of the coarse soil particles in the field soil sample
 Ws = weight of the soil particles in the field sample
 Wwc = weight of the water with coarse soil particles in the field soil sample
 Wwf = weight of the water with fine soil particles in the field/laboratory soil sample
 α = ratio of volume of the air in voids of the laboratory sample to that in the field soil
sample
 Gcγw = unit weight of the coarser fraction of soil particles in the field soil sample
 Gfγw = unit weight of the finer fraction of soil particles in the field/laboratory soil sample .

60.  The authors wish to acknowledge all the sources
(journals/books/photographs) used for the preparation of this
presentation.
Thank you.