Activity of Soil :- ($A_t$)
Activity of soil os the ratio of plasticity index and percentage of clay friction (minus 2 cu size)
where, $C%=$% of soil passing 2 cu size =% of soil finear than 2 mu $\lt 2u \rightarrow clay$
$A_t \propto (W_l-W_p)-plasticity$
$\propto Wl$ (Its compressibility)
If activity of soil is more then this soil will be more compressible or highly compressible.
Represented $\rightarrow$ shrinkage & swelling property of soil
- The clay friction F is % finer than 2 u size
- The amount of water is a soil mass depend upon the type of clay mineral present.
- Activity is a measure of the water holding capacity of clay soil. The changes in the volume of a clay in soil during swelling or shrinkage depends upon activity.
The soil containing the clay mineral:
The soil containing the clay mineral montomorillionite have been main activity $(A\gt4)$
The soil contains the mineral Kaolinite are least active $(A\lt 1)$
Whareas soil containing the mineral Illite are moderately active $(A=1 to 2)$
Depending on the activity, the soils are classified into three types.
|Sr. No.||Activity||Soil Type|
|2||A=0.75 to 1.25||Normal|
- Activity gives information about the type of effect of class mineral in a soil. The following two points are worth nothing.
- For a soil of specific origin. the activity is constant. The plastic index (P.I.) increases as the amount of class friction increases.
- Montomorillonite can produce a large increase in the plasticity even when present in small quantity.