What is Soil Stabilization?
Definition : Soil stabilization is the method to improve geotechnical properties of poor soil before construction. In simple words, the geotechnical properties of soil are modified to get the more stable soil. The stabilized soil can form the stabilized subgrade of the road.
Necessity of Soil Stabilization
- To improve the properties of weak soil to suit the traffic requirements.
- Generally to improve shear strength of weak soil.
- It is done to reduce swelling due to wetting and shrinkage stress.
- It is also done to improve the bearing capacity of soil.
- To avoid cracks in soil mass due to reduction of water content.
Soil Stabilization Methods
The following methods are used to stabilze the soil.
- Mechanical Stabilization
- Bituminous Stabilization
- Lime Stabilization
- Cement Stabilization
- Chemical Stabilization
- Miscellaneous Methods of Soil Stabilization
Mechanical Stabilization
Mechanical soil stabilization is the most generally used, simple and economical method of soil stabilization. Following three cases will be considered for sandy, clayey and without sand-clay soil where mechanical soil stabilization is done.
Case 1 : Sandy Soil. For example, when sand is present and clay is not present
Case 2 : Clayey Soil. For example, when clay is present and sand is not present
Case 3 : Sand and clay both are not present to sufficient extent.
Case 1 : Sandy Soil :
When the soil subgrade is sandy, the existing surface is cleaned. Then, the top layer of sand around 50 to 100 mm depth is removed.
It has kept side support on both sides of the subgrade surface. Then, the layer of selected soil is spread upon the surface and it is again spread by the sand which was last removed.
The selected soil and sand are mixed under optimum moisture content (OMC) condition by use of blade graders.
Mixing of both materials is carried out till uniformly of moisture and texture are attained. Final compaction process is done by use of a sheep foot roller.
Case 2 : Clayey Soil :
When the soil subgrade is clayey, the existing surface is cleaned. Then, the top layer of clay around 50 to 100 mm depth is loosened or disturbed by use of a plough.
Then, selected sand is spread and well mixed with existing loose clay. Final compaction process is done by use of a sheep foot roller.
Case 3 : Neither Sand Nor Clay is Present
When the soil subgrade does not contain sand or clay particles to a considerable extent, materials such as clay and sand are brought to site and well mixed in necessary proportion.
The mixture of sand and clay is spread on the subgrade surface. Then the final compaction process is done by sheep foot roller first and then by medium roller.
In the above three cases, the final section of road surface has a camber of 1:24 to 1:36 to drain out the rain water.
Factors affecting the Mechanical Soil Stabilization
The factors affecting the mechanical soil stabilization are described below.
Gradation :
The gradation of soil particles in such a way that voids of coarser particles is filled by fine particles to achieve high density of soil.
Compaction :
The mechanical soil stabilization depends on the degree of compaction. Generally, the compaction is done near OMC (optimum moisture content).
Soil Properties :
Normally, the soil containing higher plasticity index and higher liquidity index are most suitable for use as soil binders for surfacing.
These kinds of soil normally possess high cohesion and good moisture retention capacity. They provide a better shut against the downward flow of surface water.
Mechanical Strength of Aggregates
If mechanical strength of aggregates is high then mixed soil attains higher stability of soil.
Mineral Composition
The mechanical stability is wholly dependent on mineral composition of mixed soil. So, minerals should be weather resistant.
Bituminous Stabilization
In this method of soil stabilization, bituminous materials like asphalt and tar are generally used. Bituminous stabilization normally gets the soil stability and decreases its water absorption quality. Because of these characteristics the soil does not get eroded easily and which keeps unbroken for a longer time.
In this method, the combination of soil, clay, sand etc are also utilized with bitumen for greater results.
Lime Soil Stabilization
Lime or slaked lime is also one of the best and economical options to be used for soil stabilization.
Normally, highly clayey soil is stabilized by using slaked lime. As a result the durability and the strength of soil improves.
Whenever there is excess water content in the soil, it is removed with the use of lime, as its one of the best moisture absorbing agents.
In case of dry soil compaction, slurry lime can be used where water may be required to get effective compaction.
Cement Soil Stabilization
Cement is one of the oldest binding materials used for soil stabilization. Unlike other materials, its inter reaction is not with the soil minerals. Cement directly reacts with water exist in every soil to make the stabilization process.
There are many types of cement in the market. The type of cement wholly depends on the type of soil nature.
Chemical Stabilization
In chemical stabilization, different chemicals are added into soil to improve properties of weak soil. Calcium chlorides (CaCl2) and Sodium chlorides (Nacl) are most commonly used chemicals for soil stabilization.
Miscellaneous Soil Stabilization
Despite from above described methods of soil stabilization, there are many other methods which are also used if the above mentioned methods does not get applied to the field.
The miscellaneous soil stabilization methods are given below.
- Mass Stabilization Method
- Grouting Method
- Electrical Method
- Deep Mixing Method
FAQs on Soil Stabilization
What are the principles of soil stabilization?
Soil stabilization is the method to improve geotechnical properties of poor soil before construction. In simple words, the geotechnical properties of soil are modified to get the more stable soil. The stabilized soil can form the stabilized subgrade of the road.
What are the factors of soil stabilization?
Factors affecting soil stabilization. 1. Soil structure 2. degree of compaction 3. curing period etc.
What is a chemical method of soil stabilization?
In chemical stabilization, different chemicals are added into soil to improve properties of weak soil. Calcium chlorides (CaCl2) and Sodium chlorides (Nacl) are most commonly used chemicals for soil stabilization.
What is soil stabilization types?
Types of Soil Stabilization 1. Mechanical Stabilization 2. Bituminous Stabilization 3. Lime Soil Stabilization 4. Cement Soil Stabilization and 5. Chemical Stabilization etc.
What is three phase system of soil?
Three phase system of soil consists of solid particles, liquid and gas.
Refference :
- Soil Mechanics And Foundation Engineering (geotechnical Engineering) : Book Author – K.R Arora
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