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Unified Soil Classification System (USCS)
<br /> MAJOR DIVISIONS SYMBOL TYPICAL DESCRIPTION
<br /> r0 GW
<br /> Clean Gravels .6' Well-graded gravels,gravels,gravel-sand mixtures,little or no fines
<br /> Gravels (less than 5% ,.a GP
<br /> (more than 5o%
<br /> fines) 3 Poorly graded gravels,gravel-sand mixtures,little or no fines
<br /> •
<br /> of coarse fraction s GM
<br /> retained on No.4 Gravels with ? Silty gravels,gravel-sand-silt mixtures
<br /> COARSE sieve) Fines
<br /> GRAINED (more than 12% it 49 GC 1 gravels,gravel-sand-claymixtures
<br /> SOILS fines) Ji Clayey
<br /> (more than 5o% sw
<br /> retained on Clean Sands Well-graded sands,gravelly sands,little or no fines
<br /> No.zoo sieve) Sands (less than 5%
<br /> sP
<br /> (5o%or more fines) Poorly graded sand,gravelly sands,little or no fines
<br /> of coarse fraction
<br /> passes the No.4 sM
<br /> Sands with Silty sands,sand-silt mixtures
<br /> sieve) rr 7:
<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 fs silty clays,lean clays
<br /> FINE GRAINED than 5o) ,._..
<br /> OL
<br /> SOILS Organic Organic silts and organic silty clays of low plasticity
<br /> (50%or more
<br /> passes the MH Inorganic silts,micaceous or diatomaceous fine sands or silty soils,
<br /> No.200 sieve) elastic silt
<br /> Silts and Clays Inorganic .s CH
<br /> (liquid limit 50 or °� Inorganic clays of medium to high plasticity,sandy fat clay,
<br /> more) or gravelly fat clay
<br /> OH
<br /> Organic Organic clays of medium to high plasticity,organic silts
<br /> HIGHLY ORGANIC Primarily organic matter,dark in color, PT Peat,humus,swamp soils with high organic content(ASTM D4427)
<br /> SOILS and organic odor
<br /> Classification of Soil Constituents Grain Size Definitions
<br /> Description Sieve Number and/or Size
<br /> MAJOR 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 #200 to#40(0.08 to 0.4 mm)
<br /> Minor constituents compose 12 to 5o percent of the soil -Medium #40 to#io(0.4 to 2 mm)
<br /> and precede the major constituents(i.e.,silty SAND). Coarse #io to#4(2 to 5 mm)
<br /> Minor constituents preceded by"slightly"compose Gravel
<br /> 5 to 12 percent of the soil(i.e.,slightly silty SAND). -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 /> o-4 Very loose Under 2 Very soft Dry Absence of moisture,dusty,dry to the touch
<br /> 4-io Loose 2-4 Soft
<br /> to-3o . Medium dense 4-.8 Medium stiff 3o-5o Dense 8-15 Stiff Moist Damp but no visible water
<br /> Over 5o Very dense 15 30 Very stiff Wet Visible free water,from below water table
<br /> Over 3o Hard
<br /> Cobalt Geosciences,LLC
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<br /> (zo6)331-1097 Soil Classification Chart Figure Ci
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