1. COMPACTION OF SOIL Definition: Purpose:
It is the process of bringing the soil particles close together to a dense state by the application of energy.
Purpose:
To improve the density of soil
To improve the shear strength of soil
To improve the bearing capacity of soil
To reduce the permeability of soil
To reduce the compressibility of soil
To reduce the shrinkage of soil
To reduce the frost susceptibility of soil

2. Compaction of soil is usually required when used as a fill
The soil is commonly used as a fill material in the following cases.
To back fill an excavation e.g., for foundations.
To develop a made-up ground to support a structure.
As a sub-grade or sub-base for roads, railways or airfields
As an earth dam.
To raise the floor level to the required height in buildings.
As a back fill behind retaining walls.
To develop a site (residential, industrial, recreational etc.) in a difficult terrain (undulating topography) where substantial cutting and filling is involved.

3. Dry density ~ moisture content relationship
FACTORS AFFECTING COMPACTION OF SOIL
1. Moisture Content
Dry density ~ moisture content relationship

4. Dry density ~ moisture content curves for different compaction efforts
2. Compaction Effort or Energy
Dry density ~ moisture content curves for different compaction efforts

5. CE = (5 layers)(25 blows)(10 lb weight)(1.5 ft drop)
Compaction energy For standard AASHTO test
Compaction energy For Modified AASHTO test
CE = (5 layers)(25 blows)(10 lb weight)(1.5 ft drop)
(1/30 ft3)
= 56,250 ft-lb/ft3 ( kJ/m3)

6. Table: Specifications for Standard and Modified AASHTO Tests
No.
Item
Specifications
Standard AASHTO
Modified AASHTO 1
Volume of mold
0.944 × 10-3 m3
(1/30ft3)
(1/30 ft3) 2
Mass of hammer
2.495 kg
(5.5 lb)
4.536 kg
(10 lb) 3
Height of drop of the hammer
304.8 mm
(12 in.)
457 mm
(18 in.) 4
Number of hammer blows per layer of soil 25 5
Number of layers of compaction 6
Energy of compaction
593 kJ/m3
(12,375 ft-lb/ft3)
2698 kJ/m3
(56,250 ft-lb/ft3)

8. Dry density ~ moisture content curves for different soils
3. Soil Type
A-4, A-5
A-6, A-7-6
Water Content (%)
Dry density ~ moisture content curves for different soils

9. Material added to the soil to improve its properties
Method of Compaction
Kneading compaction
Static compaction
Dynamic compaction
Vibratory compaction
Admixture
Material added to the soil to improve its properties
Density will depend on the type and amount of admixture
Processing amount,
By thorough mixing of moisture in the soil higher dry density is achieved. Thorough mixing requires greater manipulation and curing time.
Energy distribution,
Uniform distribution of blows on each layer gives better compaction and higher dry density is obtained.

10. Standard AASHTO test equipment: (a) mould; (b) hammer

11. Where, W = weight of compacted sample in the mould
V(m) = volume of the mould = 1/30 ft3
Where,
m = moisture content
Moisture-Dry density Curve

12. Where,
γzav = Zero air-void dry density
γw = density of water
e = void ratio
Gs = specific gravity of soil solids
For 100% saturation, e = mGs
Where,
m = moisture content

13. Modified proctor test apparatus (a) mould (b) hammer

14. Standard AASHTO compaction Modified AASHTO compaction
COMPARISON OF AASHTO & MODIFIED AASHTO COMPACTION
Table Comparison of AASHTO & modified AASHTO compaction
Standard AASHTO compaction
Modified AASHTO compaction
1- Volume of the mould is 1/30ft3.
2- Weight of hammer is 5.5 lb.
3- Height of fall is 12 in.
4- Number of layers is three.
5- Number of blows is 25.
6- Maximum dry density is lower.
7- The optimum moisture content is higher.
8- The compaction curve is below and to the right of modified AASHTO curve.
9- Compaction energy applied is 12375ft-lb/ft3.
10- Compaction energy is times lower than that of the modified AASHTO test, but the maximum dry density obtained is only about 1.1 to 1.25 times lower than that of the modified AASHTO test.
11- The degree of saturation at optimum moisture content for the AASHTO & Modified AASHTO test is almost same.
2- Weight of hammer is 10 lb.
3- Height of fall is 18 in.
4- Number of layers is five.
6- Maximum dry density is higher.
7- The optimum moisture content is lower.
8- The compaction curve is above and to the left of standard AASHTO curve.
9- Compaction energy applied is 56250ft-lb/ft3.
10- Compaction energy is times higher than that of the standard AASHTO test, but the maximum dry density obtained is only about 1.1 to 1.25 times higher than that of the standard AASHTO test.

15. DETERMINATION OF FIELD DENSITY
1. Drive cylinder method
2. Sand cone method
3. Rubber balloon method
4. Nuclear density meter
DRIVE CYLINDER METHOD
Drive cylinder pushed into the soil and the surrounding soil excavated to take out the cylinder

16. The following features speed up testing.
Safest possible nuclear design as the source never leaves the meter. There is also automatic shielding when carried.
Faster testing time.
Larger samples tested: Using a new back scatter technology permits testing samples up to 20 times larger than direct transmission units.
The factory set density calibration to eliminate operator error.
The built-in brain and memory virtually eliminates need for special operator skills. The keyboard is used for all tests. The meter is factory calibrated for all materials.
The following features speed up testing.
Separate systems take moisture and density reading simultaneously to cut time to half.
Immediate display of wet and dry densities.
Lab. densities can be entered and stored in memory bank.
Immediate display of relative compaction as a % of laboratory dry density.
Storage and display of previous contact, air gap, or moisture counts for subsequent reuse if new data is not needed.
No charts or tables.
No elaborate soil preparation or hole punching.
No field calibration.

17. MERITS AND DEMERITS OF THE FIELD DENSITY METHODS
The Drive Cylinder method is easy and quick. The cutting edge is easily damaged and need re-sharpening. This method is best suited for soft and cohesive soil.
The Sand-Cone method is relatively slow, but it can be used for any type of soil.
The Water-Displacement method is a lengthy process and it can only be used on cohesive soil.
The Rubber-Balloon method is easy and quick, but the results are not very reproducible owing to the difficulty of controlling the air pressure and ensuring that the balloon conforms to the shape of the hole. The method is not applicable to very stony soils.
The Nuclear Method is considerably faster to perform than the sand-cone and rubber-balloon methods. It has the disadvantage, however, of potential hazards to individuals handling radioactive materials.

18. FIELD COMPACTION Commonly by use of rollers.
Type of roller depends on the type of soil and the degree of compaction required.
The roller may be self-propelled or towed.
The most common types of rollers are:
Smooth-wheel roller
Pneumatic rubber-tired roller
Sheep-foot roller
Vibratory roller
5. Grid roller

19. Advantages of the Improved Design of the SAKAI Rollers
The following features of the improved design of the SAKAI (JAPAN) road rollers give smooth steady rolling and excellent maneuverability for high-class compaction work.
These features ensure high performance capabilities. The rollers with these features provide better, economical and more effective compaction.
Equal drum diameter
2. Centre-pin steering
3. Independent steering for front and rear drums (axles)
4. All wheels driven

20. VIBRATORY ROLLERS Smooth drum-and-tire type vibratory roller
Pad-foot drum-and-tire type vibratory roller
Double-drum type vibratory roller
All-drum drive and vibration vibratory roller
Tractor towed vibratory roller
f Hand-guided vibratory roller

21. COMPACTING CAPABILITY OF ROLLER
The amount of material (weight or volume) compacted to the specified density by a given roller per unit time is known as the capability of roller. It depends on the following factors.
1. Working width (W)
2. Speed of roller (S)
3. Number of passes (N)
4. Thickness of layer (D)
Asphalt Compaction
Theoretical capability =
Soil Compaction
Theoretical capability =

22. Relation between dry density and number of roller passes
FACTORS AFFECTING FIELD COMPACTION
Following are the factors, which affect the field compaction.
1. Type of the compacting equipment
2. Field moisture content
3. Number of passes of the compacting equipment
4. Thickness of the lift (layer)
5. Speed of the compacting equipment
6. Soil type
Relation between dry density and number of roller passes

23. Table: General Guide to Selection of AASHTO Groups Based on Anticipated Embankment Performance
Visual Description
Maximum Dry Density lb/ft3 (kN/m3)
Optimum Moisture Content (%)
Anticipated Embankment Performance
A-1-a
Granular material
( )
7-15
Good to Excellent
A-2-4
Granular material with soil
( )
9-18
Fair to Excellent
A-3
Fine sand and sand
( )
9-15
Fair to good
A-4
Sandy silts and silts
95-130 )
10-20
Poor to good
A-5
Plastic silts and clays
85-100
( )
20-35
Unsatisfactory
A-6
Silt – clay
95-120
( )
10-30
A-7-5
Plastic silty clay
A-7-6
Clay
90-115
(14-18)
15-30
Poor to fair

24. Table: Compaction Characteristics and Ratings of the Unified Soil Classification (USC) Groups
Max. Dry Density Standard AASHTO lb/ft3 (kN/m3)
Compressibility and Expansion
Value as Embankment Material
Value as subgrade Material
Value as Base Course GW
Good: Rubber tired, smooth wheel, or vibratory roller
( )
Almost None
Very stable
Excellent
Good GP
( )
Reasonably stable
Excellent to good
Poor to fair GM
Good: Rubber tired or light sheep-foot roller
( )
Slight
Fair to poor GC
Good to fair: Rubber tired or sheep-foot roller
( )
Good to fair SW
Good: Rubber tired, or vibratory roller
( ) SP
( )
Reasonably stable when dense
Poor

25. Table: Compaction Characteristics and Ratings of the Unified Soil Classification (USC) GroupsSM
Good : Rubber tired or sheep-foot roller
( )
Slight
Reasonably stable when dense
Good to fair
Poor SC
Good to fair: Rubber tired or sheep-foot roller
( )
Slight to medium
Reasonably stable
Fair to poor ML
Good to poor: Rubber tired or sheep-foot roller
95-120
( )
Poor stability, high density required
Not suitable CL
Good to fair: Sheep-foot or rubber-tired roller.
Medium
Good stability OL
Fair to poor: Sheep-foot or rubber-tired roller
80-100
( )
Medium to high
Unstable, should not be used MH
70-95
( )
High
Poor stability, not be used CH
Fair to poor: Sheep-foot roller
80-105
( )
Very High
Fair stability, may soften on expansion
Poor to very poor OH
Fair to poor: Sheep-foot roller
65-100
( )
Very poor PT --
Very high
Should not be used

26. SPECIFICATIONS FOR FIELD COMPACTION
Where, R = relative compaction
For granular soil the term relative density as defined below is commonly used
Where, Dr = Relative density
Where Ro =

27. Fig: Most economical compaction condition
Dry density m1 m4 m3 m2
Moisture Content, m
Fig: Most economical compaction condition

28. Fig: Effect of compaction on structure of cohesive soil

29. Fig: Effect of compaction on compressibility of clayey soil
Compacted wet of optimum
Pressure (natural scale) Low-pressure consolidation
Void ratio, e
Fig: Effect of compaction on compressibility of clayey soil
Pressure (log scale) High-pressure consolidation
Compacted dry of optimum

30. Fig: Effect of compaction on the strength of clayey soils
Fig: Qualitative stress-strain curves for clay compacted on dry & wet sides of optimum
and tested at moulding moisture content as well as after soaking to produce saturation.