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Unified Soil ClassificationSystem (USCS)
<br /> � )
<br /> t MAJOR DIVISIONS SYMBOL TYPICAL DESCRIPTION
<br /> +I'II OW
<br /> Clean Gravels j i Well-graded gravels,gravels,gravel-sand mixtures,little or no fines
<br /> Gravels (less than 5% GP
<br /> (more than 5o% fines) Poorly graded gravels,gravel-sand mixtures,little or no fines
<br /> of coarse fraction "S'
<br /> GM
<br /> retained on No.4 Gravels With •, Silty gravels,gravel-sand-silt mixtures
<br /> COARSE sieve) Fines ; I
<br /> GRAINED (more than 12% , GC
<br /> SOILS fines) Clayey gravels,gravel-sand-clay mixtures
<br /> (more than 5o% sw
<br /> retained on Clean Sands Well-graded sands,gravelly sands,little or no fines
<br /> No.20o sieve) Sands (less than 5% •
<br /> (5o%or more fines) sP Poorly graded sand,gravelly sands,little or no fines
<br /> of coarse fraction
<br /> passes the No.4 sM
<br /> sieve) Sands with l Silty sands,sand-silt mixtures
<br /> Fines
<br /> (more than.12% SC
<br /> fines) Clayey sands,sand-clay mixtures
<br /> ML Inorganic silts of low to medium plasticity,sandy silts,gravelly silts,
<br /> or clayey silts with slight plasticity
<br /> Silts and Clays • Inorganic • cL Inorganic clays of low to medium plasticity,gravelly clays,sandy clays
<br /> (liquid limit less silty clays,lean clays
<br /> FINE GRAINED than 5o)
<br /> CI.SOILS
<br /> Organic Organic silts and organic silty clays of low plasticity
<br /> (5o%or more
<br /> passes the 'MY Inorganic silts,micaceous or diatomaceous fine sands or silty soils,
<br /> No.200 sieve) elastic silt
<br /> Silts and Clays Inorganic H
<br /> (liquid limit 50 or Inorganic clays of medium to high plasticity,sandy fat clay,
<br /> more) 0 or gravelly fat clay
<br /> {
<br /> Organic Organic clays of medium to high plasticity,organic silts
<br /> .4
<br /> HIGHLY ORGANIC 'Primarily organic matter,dark in color, PT
<br /> SOILS Peat,humus,swamp soils with high organic content(ASTM D4427)
<br /> and organic odor
<br /> Classification of Soil Constituents Grain Size Definitions
<br /> Description Sieve Number and/or Size
<br /> MLAJOR constituents compose more than 5o percent, • • Fines <#200(0.08 mm)
<br /> by weight,of the soil. Major constituents are capitalized• Sand
<br /> (i.e.,SAND).
<br /> -Fine #20o to#40(0.08 to 0.4 mm)
<br /> Minor constituents compose 12 to 5o percent of the soil -Medium #40 to#10(0.4 to 2 mm)
<br /> -Coarse #10 to#4(2 to 5 mm)
<br /> and precede the major constituents(i.e.,silty SAND).
<br /> Minor constituents preceded by"slightly"compose
<br /> 5 to 12 percent of the soil(i.e.,slightly silty SAND). Gravel
<br /> -Fine #4 to 3/4 inch(5 to 19 mm)
<br /> Trace constituents compose o to 5 percent of the soil -Coarse 3/4 to 3 inches(19 to 76 mm)
<br /> (i.e.,slightly silty SAND,trace gravel). Cobbles 3 to 12 inches(75 to 305 mm)
<br /> Boulders >12 inches(305 mm)
<br /> Relative Density Consistency
<br /> (Coarse Grained Soils) (Fine Grained Soils)
<br /> N,SPT, Relative N,SPT, Relative Moisture Content Definitions
<br /> Blows/FT Density Blows/FT Consistency
<br /> 0-4 Very loose Under 2 Very soft
<br /> 4-10 Loose 2-4 Soft Dry Absence of moisture,dusty,dry to the touch
<br /> 10-3o Medium dense 4-8 Medium stiff
<br /> 3o-5o Dense 8-15 Stiff Moist' Damp but no visible water
<br /> Over 5o Very dense 15-3o Very stiff
<br /> Over 3o Hard Wet Visible free water,from below water table
<br /> Cobalt Geosciences,LLC
<br /> P.O.Box 82243
<br /> , Kenmore,WA 98028 Soil Classification Chart Figure Ci
<br /> (200 331-1097
<br /> COBALT wwss'•cohaltgeo.com
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