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<br /> Unified Soil Classification System (USCS)
<br /> MAJOR DIVISIONS SYMBOL TYPICAL DESCRIPTION
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<br /> Clean Gravels *11:4 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
<br /> �;
<br /> retained on No.4 Gravels with p alfi�; GM Silty gravels,gravel-sand-silt mixtures
<br /> COARSE sieve) Fines i_i
<br /> GRAINED (more than12% ,it,11„.4 GC
<br /> SOILS fines) y�} 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% sP
<br /> (5o%or more fines) Poorly graded sand,gravelly sands,little or no fines
<br /> of coarse fraction
<br /> passes the No.4 Sands with ItsM
<br /> sieve) Silty sands,sand-silt mixtures
<br /> Fines T
<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,
<br /> (liquid limit less P ty,gravelly clays,sandy clays
<br /> FINE GRAINED than 50) silty clays,lean clays
<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 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
<br /> 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
<br /> Sand
<br /> (i.e.,SAND). -Fine #20o to#40(0.08 to 0.4 min)
<br /> Minor constituents compose 12 to 5o percent of the soil -Medium #40 to#10(0.4 to 2 mm)
<br /> and precede the major constituents(i.e.,silty SAND). -Coarse #10 to#4(2 to 5 min)
<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 min)
<br /> (i.e.,slightly silty SAND,trace gravel).
<br /> 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 /> to-3o Medium dense 4-8 Medium stiff
<br /> 3o-5o Dense 8-15 Stiff Moist Damp but no visible water
<br /> 1 Over 5o Very dense 15-3o Very stiff
<br /> Over 3o Hard Wet Visible free water,from below water table
<br /> Mil Cobalt Geosciences,LLC
<br /> P.O.Box
<br /> Kenmore,,WA WA 98028(206)331-1097 Soil Classification Chart Figure Ci
<br /> COBALT www.cobaltgeo.com
<br /> GEOSCIENCES cobaltgeoPgmail.com
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