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EXHIBIT B UNIFIED SOIL CLASSIFICATION SYSTEM UNIFIED SOIL CLASSIFICATION AND SYMBOL CHART COARSE-GRAINED SOILS (more than 50% of material Is larger than No. 200 sieve size.) Clean Gravels Less than 5% fines .~::~ Well-graded gravels, gravel-sand .:.. mixtures, little or no fines FINE-GRAINED SOILS (50% or more of material is smaller than No. 200 sieve size.) Inorganic silts and very fine sands, rock flour, silty of clayey fine sands or clayey silts with slight plasticity Inorganic clays of low to medium plasticity, gravelly clays, sandy clays, silty clays, lean clays GRAVELS More than 50% of coarse fraction larger than NO.4 sieve size SANDS 50% or more of coarse fraction smaller than NO.4 sieve size SILTS AND CLAYS Liquid limit less than 50% SILTS AND CLAYS Liquid limit 50% or greater HIGHLY ORGANIC SOILS PoorIy-graded gravels, gravel-sand mixtures, little or no fines Gravels with fines More than 12% fines Silty gravels, gravel-sand-silt mixtures ~~~ SC Clayey sands, sand-clay mixtures ML CL OL Organic silts and organic silty clays of low plasticity MH Inorganic silts, micaceous or diatomaceous fine sandy or silty soils, elastic silts CH Inorganic clays of high plasticity, fat clays OH Organic clays of medium to high plasticity, organic silts PT Peat and other highly organic soils lABORATQRY CLASSIFICATION CRITERIA CU Oso 030 GW = - greater than 4; Cc = - between 1 and 3 010 010 xOso GP Not meeting all gradation requirements for GW GM Atterberg limits below wAw Above W A W line with P.1. between line or P.l.less than 4 4 and 7 are borderline cases GC Atterberg limits above wN requiring use of dual symbols line with P.1. greater than 7 Oso 030 SW Cu = - greater than 4; Cc = - between 1 and 3 010 010 xOso SP Not meeting all gradation requirements for GW SM Atterberg limits below wAw Limits plotting in shaded zone line or P.1. less than 4 with P.1. between 4 and 7 are Atterberg limits above wAw borderline cases requiring use SC line with P.1. greater than 7 of dual symbols. Determine percentages of sand and gravel from grain-size curve. Depending on percentage of fines (fraction smaller than No. 200 sieve size). coarse-grained soils are classified as follows: Less than 5 percent . . . . . . . . . . . . . . . . . . . . . . . . . . . .. GW, GP. SW. SP More than 12 percent .. . . . . . . . . . . . . . . . . . . . . . . ... GM. GC, SM. SC 5 to 12 percent . . . . . . . . . . . . . .. Borderline cases requiring dual symbols PLASTICITY CHART 60 ~ 50 ~ >< 40 w 0 ~ 30 ~ (3 20 i= rn j 10 tl. / CH / /' ~ A LINE: PI = 0:73Cll..-2O) ../ I CL MH&OH ;/ / ......... . ML&PL .... = ~ 00 10 20 30 40 50 60 70 80 90 100 LIQUID LIMIT (lL) (Of.)