Question

Explain Compaction, Field compaction methods, Role of water content in compaction, Factors affecting compaction, the effect of compaction on the soil properties. Make sure we have some examples. Please, I want it as soon as possible, give me some good examples as well...

Answer 1

Ans) Compaction is the process in which soil particles are compressed togeather due to which water is squeezed out from voids reducing the void content in soil. Field compaction methods consist of viberations and kneading :

Vibration for coarse grained soil	Kneading for fine grained
Hand operated voberatory plates	Hand operated tampers
Motorized vibratory rollers	Sheepfoot rollers
Low frequency viberation by free falling weight	Rubber tyre rollers

Water content greately affects the compaction process. At low water content , soil is stiff and offers resistance to compaction. As the water content increases, it lubricates the soil , making compaction more easier and results in increase in density of soil.

Factors affecting compaction of soil :

1) Moisture content - As stated above, increase in water content make compactio more easier

2) Type of soil - Coarse grained soil can be compacted to higher dry density as compared to fine grained soil

3) Amount of compaction effort - The optimum water content required for compaction decreases with increase in compaction effort

4) Contact pressure - It is a pressure between the soil and wheel of equipment used for compaction. Higher contact pressure increases the dry density and lower the optimum moisture content

Now, effect of compaction on soil properties :

1) Permeability - Increase in compaction reduced the permeability

2) Compressiblity - For low pressure range, compressibilty is more for soil which is compacted to more than optimum moisture than soil compacted to less than optimum moisture. For high pressure range, compressibilty is more for soil which are compacted to less than optimum moisture than soil compacted to more than optimum moisture

3) Shear strength - Shear strength of soil is more for soil compacted to less than optimum moisture as compared to soil compacted to more than optimum moisture    

4) Soil structure - Soil compacted to less than optimum moisture have flocculated structure and soil compaced to more than optimum moisture have dispersed structure

5) Swelling and shrinkage - Higher the compaction, higher will be shrinkage and lower the swelling

6) Pore water pressure - Soil compacted to more than optimum moisture have moe pore water pressure

Examples :

Soils below pavements are compacted by moving traffic vechiles so it undergoes consolidation settlement

Soil at forest or plantations area undergoes compaction very easily because of their loose structure

Compaction increases the density of soil by about 25%

Dry density at field is achieved by compacting soil at optimum moisture content