Activity Of Clay | Activity Of Soil | Classification Of Soil Based On Activity
Activity Of Clay
The activity of clay or soil is defined as the ratio of the plasticity index and the percentage of clay friction. Thus mathematically we can express the activity of clay or soil as A= Ip / F, here Ip is the plasticity index and F is the clay friction.
We can also define the activity as the measuring tool of the water-holding capacity of the clayey soils.
A number of samples of particular soil is taken and a plot is drawn between the plastic index and clay friction. You can see in the below figure all the points for a particular soil lie on a straight line.
The slope of the line gives the activity of the soil. If the slope is steeper, the activity is greater.
The soil which has clay mineral montmorillonite has very high activity (greater than 4), the soil which has clay mineral kaolinite has very low activity (less than 1), and the soil which has clay mineral illite has moderately active (activity between 1 to 2).
More Read- Sensitivity of Soil or Clay | Classification Of Soil Based On Sensitivity
The activity plays an important role in the characteristics of the clayey soil for example changes in the value of the volume of clayey soil depending on the activity.
The activity gives information about clay minerals in the soil. The activity is constant for specific origin soil but the plasticity index increases as the amount of clay friction increases.
A small amount of highly active minerals can produce a large increase in the plasticity index.
More Read- Thixotropy Of Clay
Activity Of Clay Formula
The activity of the clay formula is A= Ip / F, here Ip is the plasticity index and F is the clay friction.
Activity Classification Of Clay
The activity of clay is classified into 3 parts which are given below.
| Classifications | Activities |
| Inactive | <0.75 |
| Normal | 0.75 to 1.25 |
| Active | > 1.25 |
Classification Of Soil Based On Activity
Soil is classified into 3 parts based on activity which is given below.
1- Inactive soil: The soil that possesses activity values less than 0.75 is known as inactive soil.
2- Normal Soil: Soil that has activity values between 0.75 to 1.25.
3- Active Soil: Active soil is those soil that has an activity value greater than 1.
More Read- Plasticity Of Soil | Why is Plasticity Of Soil Important?
Numerical On How To Find Activity Of Clay?
The activity of soil is defined as the ratio of the plasticity index to the percentage of clay friction, so mathematically we can write the Activity (A) =Ip / F.
Question– Soil has a Plastic Limit=19%, Liquid Limit= 44%, Clay Content is 24.2%, and moisture content is 29%, then find out the activity of the soil.
Solution- First we have to find out the plasticity index of soil-
The plasticity index= Liquid Limit – Plastic Limit
here liquid limit and the plastic limit are given in the question that is liquid limit= 44% and the plastic limit= 19%
So, plasticity index= 44-19=25
Now, Activity of Soil (A) =Ip / F.
The activity of soil (A)= 25/24.2= 1.033.
More Read- Consistency Limit | Atterberg’s Limit | Liquid Limit, Plastic Limit, And Shrinkage Limit
Frequently Asked Questions (FAQ)
What does the activity of clay depend on?
The activity of clay mostly depends on the surface area.
