1. Compaction Of Soil GANDHINAGAR INSTITUTE OF TECHNOLOGY Group Members
Enrollment No Name
Dave Prarthit
Deai Priyen
Dave Kaizer
Vyas Kishan
Internal Guide: Prof. Jay Parmar
Prof. Sandeep Kapadia
Gandhinagar Institute of Technology: Department of Civil Engineering

2. Outline of the presentation
Introduction
What is Compaction?
Factors affecting compaction
Effect of compaction on soil properties
Compaction of cohesive soil
Compaction of cohesive-less soil

3. Introduction
Compaction is a process by which soil particles are artificially rearranged and packed together into a closer state of contact by mechanical means in order to decrease the void ratio (porosity) of the soil and thus increase its dry density.
The compaction process may be accomplished by rolling ,tamping or vibration. Air during compaction is expelled from the void space in the soil mass,therefore the mass density is increased.

4. Principles of Compaction
Compaction of soils is achieved by reducing the volume of voids. It is assumed that the compaction process does not decrease the volume of the solids or soil grains·
uncompacted
uncompacted
compacted
compacted

5. What do you think about this live compaction machine
What is Compaction
What do you think about this live compaction machine
Heavy Weight
When loose soils are applied to a construction site, compressive mechanical  energy is applied to the soil using special equipment to densify the soil (or reduce the void ratio).
Typically applies to soils that are being applied or re-applied to a site.

6. Objectives of soil compaction
Increasing the bearing capacity of foundations.
Decreasing the undesirable settlement of structures.
Control undesirable volume changes.
Increasing the stability of slopes.

7. Mostly for laboratory test standard proctor test is performed and for the field rollers are used.
Methods of compaction

8. Factors affecting compaction
The following are the fa ctors which affect the compaction;
Compaction effort
Soil type
Moisture content
Dry unit weight
Factors affecting compaction

9. Effect of compaction effort
As the compaction effort increases,
the maximum dry unit weight of compaction increase
The optimum moisture content decreases to some extend
The preceding statements are true for all soils. Note, however, that the degree of compaction is not directly proportional to the compaction effort.
Effect of compaction effort

10. fine grain soil needs more water to reach optimum; and
Coarse grain soil needs less water to reach optimum.
Effect of soil type

11. Effect of moisture content
Below wopt (dry side of optimum):
As the water content increases, the particles develop larger and larger water films around them, which tend to “lubricate” the particles and make them easier to be moved about and reoriented into a denser configuration.
At wopt:
The density is at the maximum, and it does not increase any further.

12. Cont…. wopt (wet side of optimum):
Water starts to replace soil particles in the mold, and since ρw << ρs the dry density starts to decrease
Cont….

13. Effect of compaction on soil
When soil is compacted it affects many properties of soil such as;
1) Soil structure
2) Permeability
3) Swelling
4) Pore Water Pressure

14. Cont…. 5) Shrinkage 6) Compressibility 7) Stress-Strain Relationship
8) Shear Strength
a) Shear strength at moulded water content
b) Shear strength after saturation
Cont….

15. EFFECT ON SOIL STRUCTURE
The water content at which the soil is compacted plays an important role in soil structure.
Soils compacted at water content less than optimum water content have flocculated structure.
Soils compacted at water content more than optimum water content have dispersed structure.

16. EFFECT ON PERMEABILITY
Permeability of soil depends on void size.
As water content increases, there is an improved orientation of particles resulting in reduction of void size and permeability.
Above optimum water content ,the permeability slightly increases.
If compactive effort is increased, the permeability decreases due to increased dry density.

17. EFFECT ON SWELLING The effect of compaction is to reduce void space.
Hence swelling is enormously reduced.
Further soil compacted dry of optimum exhibits greater swell than compacted on wet side because of random orientation and deficiency of water.

18. EFFECT ON PORE WATER PRESSURE
It is defined as pressure of ground water held within a rock or soil, in gaps between particles (pores).
The pore water pressure for soil compacted dry of optimum is therefore less than that for the same soil compacted wet of optimum.

19. Soils compacted dry of optimum shrink less when compared to compacted wet of optimum.
The soils compacted wet of optimum shrink more because the soil particles in dispersed structure can pack more efficiently.
EFFECT ON SHRINKAGE

20. EFFECT ON SHEAR STRENGTH
In general, the soils compacted dry of optimum have a higher shear strength than wet of optimum at lower strains.
However at large strains the flocculated structure of soil is broken and ultimate strength will be equal for both dry and wet sides.
EFFECT ON SHEAR STRENGTH

21. EFFECT ON SHEAR STRENGTH

22. SUMMARY DRY SIDE WET SIDE STRUCTURE MORE RANDOM MORE ORIENTED
PERMEABILITY
MORE PERMEABLE
LESS PERMEABLE
COMPRESSIBILITY
MORE COMPRESSIBLE IN HIGH PRESSURE RANGE
MORE COMPRESSIBLE IN LOW PRESSURE RANGE
SWELLING
SWELL MORE
SHRINK MORE
STRENGTH
HIGHER
LESSER

23. Effect of compaction in cohesive soil
• Governed b y particle shape and mineralogy . • Interaction with water is very important. • Structure of the compacted clay is very important. • Dry of optimum - flocculated . • Wet of optimum – dispersed.
Effect of compaction in cohesive soil

24. Cohesive soil-CLAY

25. Effect of compaction on cohesionless soil

26. Typical Compaction Curve for Cohesionless Sands & Sandy Gravel
(increasing) Water content
(increasing) Density
Air dry
Complete saturation            
The low density that is obtained at
low water content is due to capillary
Forces resisting arrangements of
the sand grains.
bulking

27. Thank you 