Atterberg Limits of Soil
The term Atterberg limits is named as per the Swedish agriculturist Albert Atterberg. When water is added into a soil mass, it changes its state from solid to liquid. He divided the entire range from solid to liquid into four stages:
- The solid state
- The semi-solid state
- The plastic state
- The liquid state
He set arbitrary limits, known as Atterberg limits or consistency limits, for these division in terms of water content. Thus the Atterberg limits are the water content at which the soil mass passes from one state to the next state. These limits are presented as percentage of moisture present inside the soil. The Atterberg limits which are commonly used for engineering purposes are:
- Liquid limit
- Plastic limit
- Shrinkage limit
What is Liquid Limit of Soil?
Liquid limit is the water content corresponding to the arbitrary limit between liquid and plastic state of consistency of a soil. It is defined as the minimum water content at which the soil is still in the liquid state, but has a small shearing strength against flowing.
What is Plastic Limit of Soil?
Plastic limit is the water content corresponding to an arbitrary limit between the plastic and semi-solid states of consistency of a soil. It is defined as the minimum water content at which a soil will just begin to crumble when rolled into a thread approximately 3 mm in diameter.
What is Shrinkage Limit of Soil?
Shrinkage limit is defined as the maximum water content at which a reduction in water content will not cause a decrease in the volume of a soil mass. It is lowest water content at which a soil can still be completely saturated