SOIL CLASSIFICATION - Ms Ikmalzatul. CE 1203 : Geotechnical Properties and Construction Methods TWO KINDS of Soil... Two kinds of soil in this world…

SOIL CLASSIFICATION

-Ms Ikmalzatul

CE 1203 : Geotechnical Properties and Construction Methods

TWO KINDS of Soil...

Two kinds of soil in this world… COARSE FINE


Fine-Grained vs. Coarse-Grained Soils

U.S. Standard Sieve - No. 200 0.0029 inches 0.074 mm


Sieve Analysis (Mechanical Analysis)

This procedure is suitable for coarse grained soils

e.g. No.10 sieve …. has 10 apertures per linear inch


Hydrometer Analysis

Also called Sedimentation Analysis

Stoke’s Law

18

)(2Lsw GGD

v


Grain Size Distribution Curves


Soil Plasticity

Plasticity is a property that enables a soil to undergo deformation without breaking.

Clays for instance are moulded into earthen pots when its plastic state.

This property is characteristic on fined grained soils only, in the presence of water.

When water is replaced by some other liquid , say kerosene, the clay will behave as a granular mass.


Plasticity is due to clay minerals in the soils and is exhibited only over a specific range of moisture content.

Excessive water turns the soil into a suspension (liquid state).

With gradual decrease in the water content, the soil passes into a plastic state, then into a semi-solid (or semi-plastic) state and finally into a solid state.


WAT

ER

CONTENT

DECREASING

Liquid limit

Plastic limit

Shrinkage limit

Solid

SOLID STATE

MOISTURE CONTENT

SOLID STATE

SEMISOLID STATE

PLASTICSTATE

LIQUIDSTATE

VOLUME

Plastic state

Semi-solid state


The water content at which these changes of state occur called limits or indices.

Albert Atterberg, Swedish Soil Scientist (1846-1916)…..series of tests for evaluating soil plasticity. He defined these limits as follows: the liquid limit (LL) is the water content at which a soil passes from liquid to plastic state; the plastic limit (PL) is the water content at which a soil passes from plastic to semi-solid state; and the shrinkage limit (SL) is the water content at which a soil passes from semi solid state.


Further classification within fine-grained soils (i.e. soil that passes #200 sieve) is done based on soil plasticity.

Arthur Casagrande adopted these tests for geotechnical engineering purposes


Consistency of fine-grained soil varies in proportion to the water content

Atterberg Limits

Shrinkage limit

Plastic limit

Liquid limit

solid

semi-solid

plastic

liquid

PlasticityIndex

(cheese)

(pea soup)

(pea nut butter)

(hard candy)


Liquid Limit (LL or wL)

Empirical Definition

The moisture content at which a 2 mm-wide groove in a soil pat will close for a distance of 0.5 in when dropped 25 times in a standard brass cup falling 1 cm each time at a rate of 2 drops/sec in a standard liquid limit device


Engineering Characterization of Soils

Soil Properties that Control its Engineering Behavior

Particle Size

Particle/Grain Size DistributionParticle Shape

Soil Plasticity

fine-grained

coarse-grained


Clay Morphology

Scanning Electron Microscope (SEM)

Shows that clay particles consist of stacks of plate-like layers


Soil Consistency Limits Albert Atterberg (1846-

1916) Swedish Soil Scientist ….. Developed series of tests for evaluating consistency limits of soil (1911)

Arthur Casagrande (1902-1981)

……Adopted these tests for geotechnical engineering purposes


Arthur Casagrande (1902-1981)

Joined Karl Terzaghi at MIT in 1926 as his graduate student

Research project funded by Bureau of Public Roads

After completion of Ph.D at MIT Casagrande initiated Geotechnical Engineering Program at Harvard

Soil Plasticity and Soil Classification (1932)


Casagrande Apparatus






Liquid Limit Determination


The moisture content at which a thread of soil just begins to crack and crumble when rolled to a diameter of 1/8 inches

Plastic Limit (PL, wP)


Plastic Limit (PL, wP)


Plasticity Index ( PI, IP )

PI = LL – PL

or IP=wL-wP

Note: These are water contents, but the percentage sign is not typically shown.


Plasticity Chart


USCS Classification Chart


USCS Classification Chart


Plasticity Chart

THE END

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SOIL CLASSIFICATION - Ms Ikmalzatul. CE 1203 : Geotechnical Properties and Construction Methods TWO KINDS of Soil... Two kinds of soil in this world…