soil plasticity and clay minerology

1. Plasticity Characteristics of soils
Geo-Technical Engineering-1
Aldel Education Trust
St John College of Engineering and Management, Palghar
Mr. Naveen H

2. Detailed Syllabus
● Plasticity of soil: Definition of plasticity of soil, reason of plasticity,
consistency of soil, explanation about idea set by Atterberg in defining the
three states of soil, definition & determination of liquid limit, plastic limit,
shrinkage limit
● Definitions of shrinkage parameters; plasticity index, shrinkage index,
liquidity index, consistency index, flow index, toughness index, activity,
sensitivity and thixotropy of soils. Use of consistency limits
● Explanation about clay minerals e.g. montmorillonite, illite, and kaolinite;
their formation and role in producing the plastic behavior in soil

3. Consistency of Soil
Consistency of Soil : Soil consistency is the strength with which soil materials
are held together or the resistance of soils to deformation and rupture.
Consistency denotes degree of firmness of the soil which may be termed as
Soft, Firm, Stiff or Hard
In 1911, a Swedish agriculture engineer Atterberg mentioned that fine grained
soil can exist in four states, namely
● Liquid state
● Plastic state
● Semi-solid state
● Solid state

4. Elasticity & Plasticity
Elasticity is the property of a body to recover its
original configuration (shape and size) when you
remove the deforming forces.
Plasticity is the property of a body to lose its
property of elasticity and acquire a permanent
deformation on the removal of deforming force.

5. Consistency of Soil
He set arbitrary limits, knows as consistency Limits or Atterberg limits.
● Liquid Limit
● Plastic Limit
● Shrinkage Limit.

6. Liquid Limit
Liquid Limit is the water content corresponding to the
arbitrary limit between liquid and plastic state of
consistency of the soil.
It is defined as the minimum water content at which
soil is still in the liquid state,but has a small shearing
strength against flowing. Which can be measured by
standard Liquid limit device.

8. Liquid Limit

9. Plastic Limit
Plastic Limit is the water content corresponding to the arbitrary limit
between Plastic and Semi-Solid state of consistency of the soil.
It is defined as the minimum water content at which soil will begin to
crumble when rolled into a tread approximately 3 mm in diameter..
Which can be measured by Plastic limit device.

10. Plastic Limit

11. Shrinkage Limit
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 at which a soil can still be
completely saturated.

12. Shrinkage Limit

13. Plasticity Index
The range of consistency within which a soil exhibits plastic properties is called Plastic range and is
indicated by Plasticity index.
The Plasticity index is defined as the numerical difference between the liquid limit and the plastic
limit of a soil.
Ip = LL-PL
Consistency Index
The consistency index or the relative consistency is defined as the ratio of the liquid limit minus the
natural water content to the plasticity index of a soil.
Ic = LL- w
Ip

14. Plasticity
Plasticity is defined as that property of a soil which allows it to be deformed rapidly, without
rupture, without elastic rebound, and without volume change.
Liquidity Index
The Liquidity index or water-plasticity ratio is the ratio, expressed as a percentage, of the
natural water content of a soil minus its plastic limit, to its plasticity index
IL = w - PL
Ip
The Liquidity index or water-plasticity ratio is the ratio, expressed as a percentage, of the
natural water content of a soil minus its plastic limit, to its plasticity index
IL = w - PL
Ip

15. Sensitivity of Clays
The Consistency of an undisturbed sample of clay is altered, even at the same water content,
if it is remoulded. It is because the original structure of clay is altered by remoulding or
reworking.
Sensitivity is defined as the ratio of itd unconfined compressive strength in the natural or
undisturbed state to that in the remoulded state, without change in the water content.
Thixotropy of Clay

16. Clay Mineral
● Silica tetrahedral unit
● Octahedral unit

17. Thank you