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1 <br /> UNIFIED SOIL CLASSIFICATION SYSTEM <br /> ICriteria for Assigning Group Symbols and Group Names Using Laboratory Tests" Soil Classification <br /> Group <br /> Symbol Group NameB <br /> I Coarse Grained Soils Gravels Clean Gravels Cu a 4 and 1<_Cc.<..3E GW Well graded graver <br /> More than 50%retained More than 50%of coarse Less than 5%fines Cu<4 and/or 1 >Cc>3' GP Poorly graded gravel` <br /> fraction retained on <br /> on No.200 sieve No.4 sieve Gravels with Fines Fines classify as ML or MH GM Silty gravel`" <br /> I More than 12%fines' Fines classify as CL or CH GC Clayey graver'." <br /> Sands Clean Sands Cu>_6 and 1<_Cc-5.3E SW Well-graded sand' <br /> 50%or more of coarse Less than 5%fines° Cu<6 and/or 1 >Cc>3` SP Poorly graded sand` <br /> fraction passes <br /> IIINo.4 sieve Sands with Fines Fines classify as ML or MH SM Silty sandy"•' <br /> More than 12%fines° Fines Classify as CL or CH SC Clayey sandyH.' <br /> Fine-Grained Soils Silts and Clays inorganic PI>7 and plots on or above"A"lined CL Lean clay"•`•M <br /> 50%or more passes the Liquid limit less than 50I <br /> PI<4 or plots below"A"tine' ML SiltK.L,M <br /> No.200 sieve KMN <br /> organic Liquid limit-oven dried <0:75 OL Organic clay•L <br /> Liquid limit-not dried Organic silt'< ° <br /> I Silts and Clays Liquid limit 50 or more inorganic PI plots on or above"A"line CH Fat clay"`M <br /> PI plots below"A"line MH Elastic Silt'•`M <br /> organic Liquid limit-oven dried 0.75 OH Organic clayK'-M' <br /> Liquid limit-not dried Organic silt".`t° <br /> Highly organic soils Primarily organic matter,dark in color,and organic odor PT Peat <br /> 1 ASased on the material passing the 3-in.(75-mm)sieve "If fines are organic,add"with organic fines"to group name. <br /> BIf field sample contained cobbles or boulders,or both,add"with cobbles I If soil contains.. 15%gravel,add"with gravel"to group name. <br /> or boulders,or both"to group name. 'elf Atterberg limits plot in shaded area,soil is a CL-ML,silty clay. <br /> III °Gravels with 5 to 12%fines require dual symbols: GW-GM well-graded Klf soil contains 15 to 29%plus No.200,add"with sand"or"with <br /> gravel with silt,GW-GC well-graded gravel with clay,GP GM poorly gravel,"whichever is predominant. <br /> ograded gravel with silt,GP-GC poorly graded gravel with clay. L If soil contains.>_30%plus No.200 predominantly sand,add <br /> Sands with 5 to 12%fines require dual symbols: SW-SM well-gradedI <br /> "sandy"to group name. <br /> sand with silt,SW-SC well-graded sand with clay,SP-SM poorly graded M <br /> sand with silt,SP-SC poorly graded sand with clay If soil contains>_30%plus No.200,predominantly gravel, <br /> add"gravelly"to group name. <br /> e (D30)2 "PI>_4 and plots on or above"A"line. <br /> Cu=Dso/Dio Cc I <br /> Dio x Dsa ° PI<4 or plots below"A"line. <br /> Elf soil contains>_15%sand,add"with sand"to group name. PPI plots on or above"A"line. <br /> °If fines classify as CL-ML,use dual symbol GC-GM,or SC-SM. ° PI plots below"A"line. <br /> I 60 <br /> For classification of fine-grained z j <br /> soils and fine-grained fraction j <br /> I <br /> I r- of coarse-grained soils ��. <br /> Equation of"A"-line P <br /> Horizontal at P1=4 to LL=25 a ,,•.' <br /> X 40 ..... then P1=0:73 ILL 20) .......__ *Zs <br /> I <br /> 2 Equation of U"-line �'� <br /> Vertical at LL 46 to PI_7 ; <br /> 30 then PI .O ILL-S) 7< <br /> I... 0. <br /> I fol 20 <br /> MH or OH • <br /> • <br /> • <br /> 4 3 AFL or OL <br /> I E_ • <br /> 0 10 16 20 30 40 50 60 70 80 90 100 110 <br /> ILIQUID LIMIT ILL) <br /> I <br />