Answer:
PLASTICITY CHARACTERISTICS OF SOILS
The plasticity of a soil is its ability to undergo deformation without cracking. It is an
important index property of fine grained soil, especially for clayey soils. The adsorbed
water in clayey soils is leads to the plasticity of soil. Adsorbed water in the clay
particles allow the particles to slip over one another. The particles do not return to its
original position following the deformation of soil. The soil becomes plastic only when it
has clay minerals.
ATTERBERG LIMITS
1n 1911, A Swedish agriculture engineer Atterberg mentioned that a fine grained soil
can exist in four states, namely, liquid, plastic, semi-solid or solid. The water content at
which the soil changes from one state to other are known as Atterberg limits or
Consistency limits.
It is very important properties of fine grained soils.
There are three atterberg limits:
Liquid limit: The water content at which the soil changes from the liquid state to
plastic state is known as liquid limit. In other words, the liquid limit is the water
content at which the soil ceases to be liquid.
Plastic Limit: The water content at which the soil becomes semi-solid is known as
plastic limit.
Shrinkage Limit: The water content at which the soil changes from semi-solid to solid
state is known as the shrinkage limit.
DETERMINATION OF SHRINKAGE LIMIT
Shrinkage limit is the smallest water content at which the soil is saturated. It is also
define as the maximum water content at which a reduction of water content will not
cause a decrease in the volume of the soil mass
Weight of water in stage (I), = −
Loss of weight of water from stage (I) to stage (II), = 1 − 2
Weight of water in stage (II), = 1 − − 1 − 2
From definition, shrinkage limit = water content in stage (II),
= 1 − − 1 − 2
= 1 − 1 − 2
Where, 1 is the water content in stage