Soil improvement for construction of any structure

We depend upon infrastructure like roads, skyscraper, railways and dams etc completely. We tries to improve the infrastructure But if our structure is on poor soil that ultimately affect the structure and result into cracks and may even collapse-loss of wealth and many precises lives. Then there is need of ground improvement before construction of any structure to increase its durability and strength.
There are some major reason for poor quality of ground for construction:

• Swelling and shrinkage of soil

• Collapsible soil

• Soft soil

• Organic soil and peaty soil

• Foundation on landfill or dump area

• Liquefaction of soil

There are various techniques used for soil improvement. Few of them are
1.Compaction: The process in which density of soil increases by an external factor.The purpose is to increase shear strength and reduces liquefaction affect, permeability and compressibility. It is further divided into  two type:

a. Shallow compaction:

• Smooth-wheel roller
• Sheepsfoot roller
• Impact roller
• Vibrating plates

b. Deep compaction:

• Dynamic Compaction
• Vibro-Compaction
• Compaction Grouting
• Pre-fabricated Vertical Drains
•  Blast densification

2. Dewatering: It is process in which water in soil and any solid substance is removed. Pumps,wells point and deep well with pumps are some examples of dewatering.

3. Heating and Freezing method:
 In heating method,the water inside the soil evaporated due to exposure in the heat produced by external source. It is not used everywhere as it requires a lot of energy. The various method for heating are

• Ground surface heating
• Heating through boreholes
• Use of thermally stabilized building blocksThermal pile.

In freezing method,the gound is freezed to form a temporary water bearing strata and to increase compressive strength of soil.

These strata act as resistive layer which stop entering water in excavation. After constructing the structure, the freezing process is stopped. The effectiveness of freezing is depend upon presence of water and cementing particle.
We can do freezing in following ways:

• By injected coolant like liquid nitrogen into ground.
• By circulation of coolant into ground through tubes inserted into  ground.

4. Soil retaining wall: The wall is generally 

 made up of  concrete precasted blocks.It act as barriers to soil. It is used due to less cost, easy handling and higher strength and stability.

5. Reinforced ground with soil nailing: In soil nailing process the long steel bars are inserted in the soil to support the external face and prevent collapse. The process proceed from top to bottom. Shortcrete also applied after insertes the nails in the soil. Thus the nail provide support to external reinforced wall.The only condition is that the nailing should be above the water table.

6. Grouting: It is process in which pores and cavities are filled with liquid cementous material. The purpose is to increase shear strength and decrease permeability of soil. It is further divided into following types depending upon the  type of material used:

• Cementous material(gravely material)
• Suspension material (For sand)
• Emulsion like chemical grouting
• Liquid material

It is of 4 types :

• Penetration grouting
•  Displacement grouting
• Compaction grouting
• Grouting of Voids
• Jet grouting

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