SOIL CLASSIFICATION -Ms Ikmalzatul

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

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.

Plastic state Semi-solid state VOLUME MOISTURE CONTENT SOLID STATE WA T ER CONT ENT DECREAS ING Liquid limit Plastic limit Shrinkage limit Solid SOLID STATE MOISTURE CONTENT SOLID STATE SEMI PLASTIC LIQUID 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 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

Atterberg Limits Consistency of fine-grained soil varies in proportion to the water content Shrinkage limit Plastic limit Liquid limit solid semi-solid plastic liquid Plasticity Index (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 coarse-grained fine-grained Particle/Grain Size Distribution Particle Shape Soil Plasticity

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

Casagrande Apparatus

Casagrande Apparatus

Liquid Limit Determination

Plastic Limit (PL, wP) 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)

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

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