Soil improvement in its broadest sense is the alteration of any property of a soil to improve its engineering performance such as strength, reduced compressibility, reduced permeability, or improved ground water condition. This may be either a temporary process to permit the construction of a facility or may be a permanent measure to improve the performance of the completed facility. We will discuss about the details of soil improvement.
Techniques of Soil ImprovementThere are various techniques used for the improvement of the soil based on the construction activity and type of soil. The soil improvement techniques are,
- Surface Compaction
- Drainage Methods
- Vibration Methods
- Precompression and consolidation
- Grouting and Injection
- Chemical Stabilisation
- Soil Reinforcement
- Geo textiles and Geo membranes
- Other Methods
1. Surface CompactionOne of the oldest methods of soil densification is surface compaction. Construction of a new road, a runway, an embankment or any soft or loose site needs a compacted base for laying the structure. If the depth to be densified is less, the surface compaction alone can solve the problem. The usual surface compaction devices are rollers, tampers and rammers. All conventional rollers like smooth wheel, rubber-tyred, sheep foot, vibratory and grid rollers can be used.
2. Drainage MethodsGround water is one of the most difficult problems in excavation work. The presence of water increases the pore water pressure and decreases the shear strength. Further heavy inflow of water to the excavations is liable to cause erosion or collapse of the sides of open excavations. Certain methods are available to control the ground water and ensure a safe and economical construction scheme. Common drainage methods are Well-point Systems, Deep- well Drainage, Vacuum Dewatering system, Dewatering by Electro-osmosis etc
3. Vibration MethodsVibration methods can be effectively used for rapid densification of saturated non-cohesive soils. Vibrations and shock waves in loose deposits of such materials cause liquefaction followed by densification accompanying the dissipation of excess pore water pressures. Some of the mostly adopted vibration methods are blasting, Vibrating probe, Vibratory rollers, Vibro-displacement Compaction Piles, Vibrofloatation, Heavy Tamping etc.
4. Pre-Compression and ConsolidationThis method aims to consolidate the soil before construction. Various techniques adopted are Preloading and Surcharge Fills, Vertical Drains, Dynamic Consolidation, Electro osmotic Consolidation etc.
5. Grouting and InjectionGrouting is a process whereby stabilizers, either in the form of suspension or solution are injected into subsurface soil or rock for one or more of the following applications:
- Control of ground water during construction
- Void filling to prevent excessive settlement
- Strengthening adjacent foundation soils to protect them against damage during excavation, Pile driving, etc.
- Soil Strengthening to reduce lateral support requirements
- Stabilization of loose sands against Liquefaction
- Foundation Underpinning
- Reduction of machine foundation vibrations