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Soil improvement methods are adopted to increase the shear strength and the density of soil, preventing the occurrence of liquefaction and providing sufficient bearing capacity to the foundation.
The selection of soil improvement methods is governed by several factors like soil condition/type, effective treatment depth, material and equipment availability, and relative cost.
The tables below help in selecting the best suitable soil improvement methods out of the following method-
- In-Situ Deep Compaction of Cohesionless Soils
- Injection and Grouting
1. In-Situ Deep Compaction of Cohesionless Soils
It is a technique used for in-situ densification of cohesive soil deposits by heavy impact, vibration, and blasting. It involves the rearrangement of the cohesionless soil structure from a loose to a dense state.
2. Injection and Grouting
Injecting and grouting improve the strength and stiffness of the soil by high-pressure injection of a cementitious grout mix through a small-diameter casing at a pre-determined depth. This type of soil improvement method is used in the construction of dams, lock structures, and tunnels.
Pre-compression is a ground improvement method that compresses the ground under applied pressure before putting or finishing the structural load. Pre-compression is accomplished in two ways:
- Ground pre-compression is accomplished by pre-loading, which entails installing and removing earth, water, or some other dead load before construction that is equivalent in weight to the final load.
- Surcharging occurs when the stress intensity from the pre-loading is larger than the intensity from the final loading.
The modification of any one or more of the soil properties improves the strength of soil and decreases shrink-swell soil characteristics by using admixtures such as lime, cement, and cohesive-non-swelling (CNS) layer.
Thermal soil improvement is carried out in 2 methods-
Heating: The removal of heat from the soil, turning its pore water into ice, is a powerful technique that renders the ground impermeable and makes them more robust for unconsolidated materials.
Freezing: Applying heat to clays to drive out free pore water and, at higher temperatures, the water adsorbed on particle surfaces creates a tough, durable material, as when making brick or mud building blocks.
Reinforced soil reinforcement is a technique used to improve the stiffness and strength of soil using methods such as reinforced soil, soil nailing, root or micro-piles, slope dowels, and embankment piles.