Tut 1 (b) - Soil Classification PDF

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SOIL CLASSIFICATION FLOW CHART FOR SOIL CLASSIFICATION

Cu ≥ 6

Cu ≥ 6

(Adapted from ASTM: D2487 - 06)

USCS SYMBOLS Symbols G S M C W P H L

GRADING PARAMETERS (Cu & Cc)

Noun Gravel Sand Silt Clay

Adjective Gravelly Sandy Silty Clayey Well-graded Poorly graded

High plasticity Low plasticity

If the fine portion < 12%, for Gravels, the shape of grading curves should satisfy: ❖ Coefficient of uniformity (Cu): Well-graded ❖ Coefficient of curvature (Cc): If one of the above conditions is not satisfactory → Poorly graded If the fine portion < 12%, for Sands, the shape of grading curves should satisfy:

SIEVE NUMBERS & SOIL PARTICLES

❖ Coefficient of uniformity (Cu): Well-graded

Sieve No# and Particle Size

❖ Coefficient of curvature (Cc):

1/ 2

3/ 4 1/ 4

Gravel

If one of the above conditions is not satisfactory → Poorly graded

PLASTICITY CHART Sand

Silt: 2μm – 75μm

Clay: less than 2μm

COEFFICIENT OF PERMEABILITY Coefficient of Permeability 10-10 10-9 10-8 10-7 10-6 10-5 10-4 10-3 10-2 10-1 100

Clays

Silts Sands Fines ← → Coarse

Gravels

Soils exhibit a wide range of permeabilities

ATTERBERG LIMITS

Liquid Limit (LL): the minimum moisture content (wLL) at which a soil will flow under its own weight. Plastic Limit (PL): the minimum moisture content (wPL) at which a soil still behaves plastically (i.e., a soil can be rolled into a thread 3mm in diameter without crushing or breaking). Shrinkage Limit (SL): the moisture content (wSL) where further loss of moisture will not result in soil volume reduction

GRADATION TYPES...