Explain various factors affecting compaction.

Some of the factors which affect compaction are as follows:

1. Water Content 
2. Amount of compaction 
3. Type of soil
4. Method of compaction 
5. Admixtures 

At low water content, the soil is stiff and offers more resistance to compaction. The dry density of the soil increases with an increase in the water content till the optimum water content is reached. At that stage, the air voids attains approximately a constant volume. With further increase in water content, the air voids do not decrease but the total voids (air plus water ) increase and the dry density decreases. Thus, the higher dry density is achieved up to the optimum water content due to forcing air out if the soil voids.

The amount of compaction greatly affect the maximum dry density and optimum water content of a given soil. The effect of increasing the compaction result in an increase in the maximum dry density and dec....

Some of the factors which affect compaction are as follows:

1. Water Content 
2. Amount of compaction 
3. Type of soil
4. Method of compaction 
5. Admixtures 

Water content:

At low water content, the soil is stiff and offers more resistance to compaction. The dry density of the soil increases with an increase in the water content till the optimum water content is reached. At that stage, the air voids attains approximately a constant volume. With further increase in water content, the air voids do not decrease but the total voids (air plus water ) increase and the dry density decreases. Thus, the higher dry density is achieved up to the optimum water content due to forcing air out if the soil voids.

Amount of compaction:

The amount of compaction greatly affect the maximum dry density and optimum water content of a given soil. The effect of increasing the compaction result in an increase in the maximum dry density and decreases in the optimum water content as shown in figure.

Type of soils:

The maximum dry density depend upon the type of the soil. Coarse grained soil can be compacted to higher dry density than fine grained soils. With the addition of even a small quantity of fines to a coarse grained soil, the soil attains a much higher dry density for the same compactive effort . However, if the quantity of fines is increased to a value more than that required to fill the voids of the course grained soils, the maximum dry density decreases. A well graded sand attains a much higher dry density than a poorly graded soil.

Method of compaction:

The density of obtained during compaction, for a given soil, greatly depends upon the type of compaction or the manner in which the compactive effort is applied. The various variables in this respect are:

• weight of the compacting equipment,
• the manner of operation such as dynamic or impact, static, kneading or rolling and ,
• the time and area of contact between the compacting element and the soil.

Admixtures:

The compaction characteristic of the soil can be improved by adding other materials, known as admixtures. The most commonly used admixtures are lime, cement and bitumen. The dry density achieved depends upon the type and amount of admixtures.