Sensitivity

1. The breakfast bond between solid molecules of soil
2. Permanent loss : Suppose, $q_u=100$, $q_v=20$
   $S_t=\frac{100}{20}=5$
   Loss of compress strength recorded = $100-20=80%$
3. Due to the re-orientation of water molecules present in the absorbed layer of soil.
4. Temporary loss
5. Completely recover with time. Thixotropy:
   Over a period of time soil regains a part of pt's lossed strength on the account of rehababilation of water molecules in adsorbe layer of soil solid. But, the strength loss on the account of permanent distinction of soil is not regained by soil.
   High Sensitive soils are always reflects high thix value.

Activity of Soil ($A_t$)

(Scientics :- Skemptom)
Activity of soil is the ratio of plasticity index and percentage of clay friction
$A_T=\frac{I_p}{f}$
$I_p$ Plasticity Index
$f$ class friction $A_t=\frac{W_l-W_P}{C %}$ **Conclusion** $A_T\propto=(W_L-W_P) Plasticity$ $\propto W_L (its compressibility)$ So, If Activity of soil is more than this soil will be more compressible or highly compressible Represented --\gt Shrinkage & Swelling property of soil 1. The clay friction F is % finer than 2 $\mu$ size. 2. The amount of water in a soil mass depends upon the type of clay mineral present 3. Activity is a measure of the water holding capacity of clay soil. The changes in the volume of classes soil during swelling or shrinkage depends upon activity. The soil containing the clay mineral:-
- Kaolinite - Iilite - Montmorillonite

• The soil containing the clay mineral montmorillonite have high main activity (A>4)
• The soil containing the mineral Kaolinite are least active (A<1)
• Whereas soil containing the mineral illite are moderately active (A= 1 to 2)
• Depending upon the activity, the soil are classified into three types.
• Activity gives information about the type add effect of clay mineral in a soil. The following two points are worth noting
  * For a soil of specific origin, the activity is constant. The plastic index (P.I) increases as the amount of clay friction increases.
  * Montomonilionite, can produce a large increase in the plasticity index even when present in small quantity.