compaction 1

7/27/2019 Compaction 1

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Soil Compaction

Compaction

Compaction is a process by which the soil particles are

artificially rearranged and packed together into a

closer state of contact by mechanical means in order

to decrease the porosity (or voids ratio) of the soil and

thus increase its dry density.



Applications of Compaction

1. Compaction of foundation soil for house construction.

2. Compaction of soil/gravel/crushed rock/asphalt in road &

pavement construction.

3. Compaction of soil in earth embankments.

4. Compaction of soil behind retaining walls.

5. Compaction of soil backfill in trenches.

6. Dam construction

7. Construction of clay liners for waste storage areas

8. Ground improvement



STANDARD PROCTOR’S TEST



Fig. Moisture content versus dry density at a particular compactive effort



Factors affecting Compaction

•

Water content (moisture content)

• Amount of compaction

• Type of soil

• Method of compaction

•

Admixtures



1. Water content (moisture content)

Fig. Moisture content versus dry density at a particular compactive effort



2. Amount of compaction

Fig. Effect of compactive effort on compaction characteristics



3. Type Of Soil



1- Rammers

2- Vibratory Plates

3- Smooth Rollers

4- Rubber-Tire

5- Sheep foot Roller

6- Dynamic Compaction

4. Method of compaction



5. Admixtures

1. Stabilizing agents are the admixtures added to soil.

2. The effect of adding these admixtures is to stabilize the soil.

3. In many cases they accelerate the process of densification.

• Lime

• Sodium hydroxide

• Sodium Carbonate

• Calcium Chloride

• Flyash



Effect of Compaction on Soil Properties

• Soil Structure

• Permeability

• Shrinkage

•

Swelling• Pore Pressure

• Compressibility

• Shear Strength

• Stress Strain Characteristics



Soil Structure

Fine grained soil

1. On dry side of optimum, the structure is flocculated. The particles

repel and density is less.

2. Addition of water increases lubrication and transforms the structurein to dispersed structure

Coarse grained soil,

single grained structure is maintained

Composite soil,

behaviour depends on composition.



Permeability1. Increased dry density, permeability.

2. At same density, soil compacted dry of optimum is more

permeable.3. At same void ratio, soil with bigger particle size is more

permeable.

4. Increased compactive effort reduces permeability.

ShrinkageSoil sample compacted dry of optimum shrink appreciably

less than the sample compacted wet of optimum.

SwellingClayey Soil sample compacted dry of optimum exert greater

swelling pressure and swell to higher water content



Pore Pressure1. Clayey soil compacted dry of optimum develops less pore

water pressure than that compacted wet of optimum at

the same density at low strains.2. However, at higher strains the effect is the same in both the

cases.

CompressibilityAt low pressure, soil compacted wet of optimum shows more

compressibility than that on dry side. But at higher pressure,

behaviour is similar.

compaction 1

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