Designation: D 2487 – 06Standard Practice forClassification of Soils for Engineering Purposes (UnifiedSoil Classification System)1This standard is issued under the fixed designation D 2487; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.grande in the early 1940’s.2 It became known as the UnifiedSoil Classification System when several U.S. GovernmentAgencies adopted a modified version of the Airfield System in1952.1.6 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.1.7 This practice offers a set of instructions for performingone or more specific operations. This document cannot replaceeducation or experience and should be used in conjunctionwith professional judgment. Not all aspects of this practice maybe applicable in all circumstances. This ASTM standard is notintended to represent or replace the standard of care by whichthe adequacy of a given professional service must be judged,nor should this document be applied without consideration ofa project’s many unique aspects. The word “Standard” in thetitle of this document means only that the document has beenapproved through the ASTM consensus process.1. Scope*1.1 This practice describes a system for classifying mineraland organo-mineral soils for engineering purposes based onlaboratory determination of particle-size characteristics, liquidlimit, and plasticity index and shall be used when preciseclassification is required.NOTE 1—Use of this standard will result in a single classification groupsymbol and group name except when a soil contains 5 to 12 % fines orwhen the plot of the liquid limit and plasticity index values falls into thecrosshatched area of the plasticity chart. In these two cases, a dual symbolis used, for example, GP-GM, CL-ML. When the laboratory test resultsindicate that the soil is close to another soil classification group, theborderline condition can be indicated with two symbols separated by aslash. The first symbol should be the one based on this standard, forexample, CL/CH, GM/SM, SC/CL. Borderline symbols are particularlyuseful when the liquid limit value of clayey soils is close to 50. These soilscan have expansive characteristics and the use of a borderline symbol(CL/CH, CH/CL) will alert the user of the assigned classifications ofexpansive potential.1.2 The group symbol portion of this system is based onlaboratory tests performed on the portion of a soil samplepassing the 3-in. (75-mm) sieve (see Specification E 11).1.3 As a classification system, this standard is limited tonaturally occurring soils.2. Referenced Documents2.1 ASTM Standards: 3C 117 Test Method for Materials Finer than 75-µm (No.200) Sieve in Mineral Aggregates by WashingC 136 Test Method for Sieve Analysis of Fine and CoarseAggregatesC 702 Practice for Reducing Samples of Aggregate toTesting SizeD 420 Guide to Site Characterization for Engineering Design and Construction PurposesD 422 Test Method for Particle-Size Analysis of SoilsD 653 Terminology Relating to Soil, Rock, and ContainedFluidsNOTE 2—The group names and symbols used in this test method maybe used as a descriptive system applied to such materials as shale,claystone, shells, crushed rock, etc. See Appendix X2.1.4 This standard is for qualitative application only.NOTE 3—When quantitative information is required for detailed designs of important structures, this test method must be supplemented bylaboratory tests or other quantitative data to determine performancecharacteristics under expected field conditions.1.5 This standard is the ASTM version of the Unified SoilClassification System. The basis for the classification schemeis the Airfield Classification System developed by A. Casa-2Casagrande, A., “Classification and Identification of Soils,” Transactions,ASCE, 1948, p. 901.3For referenced ASTM standards, visit the ASTM website,, orcontact ASTM Customer Service at [email protected] For Annual Book of ASTMStandards volume information, refer to the standard’s Document Summary page onthe ASTM website.1This standard is under the jurisdiction of ASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.07 on Identification andClassification of Soils.Current edition approved May 1, 2006. Published June 2006. Originallyapproved in 1966. Last previous edition approved in 2000 as D 2487 – 00.*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.1

D 2487 – 06Fine—passes 3 4-in. (19-mm) sieve and retained on No. 4(4.75-mm) sieve.3.1.3 organic clay—a clay with sufficient organic content toinfluence the soil properties. For classification, an organic clayis a soil that would be classified as a clay except that its liquidlimit value after oven drying is less than 75 % of its liquid limitvalue before oven drying.3.1.4 organic silt—a silt with sufficient organic content toinfluence the soil properties. For classification, an organic siltis a soil that would be classified as a silt except that its liquidlimit value after oven drying is less than 75 % of its liquid limitvalue before oven drying.3.1.5 peat—a soil composed of vegetable tissue in variousstages of decomposition usually with an organic odor, adark-brown to black color, a spongy consistency, and a textureranging from fibrous to amorphous.3.1.6 sand—particles of rock that will pass a No. 4 (4.75mm) sieve and be retained on a No. 200 (75-µm) U.S. standardsieve with the following subdivisions:Coarse—passes No. 4 (4.75-mm) sieve and retained on No.10 (2.00-mm) sieve,Medium—passes No. 10 (2.00-mm) sieve and retained onNo. 40 (425-µm) sieve, andFine—passes No. 40 (425-µm) sieve and retained on No.200 (75-µm) sieve.3.1.7 silt—soil passing a No. 200 (75-µm) U.S. standardsieve that is nonplastic or very slightly plastic and that exhibitslittle or no strength when air dry. For classification, a silt is afine-grained soil, or the fine-grained portion of a soil, with aplasticity index less than 4 or if the plot of plasticity indexversus liquid limit falls below the “A” line.3.2 Definitions of Terms Specific to This Standard:3.2.1 coeffıcient of curvature, Cc—the ratio (D 30 ) 2 /(D10 3 D60), where D60, D30, and D10 are the particle sizescorresponding to 60, 30, and 10 % finer on the cumulativeparticle-size distribution curve, respectively.3.2.2 coeffıcient of uniformity, Cu—the ratio D60/D10, whereD60 and D10 are the particle diameters corresponding to 60 and10 % finer on the cumulative particle-size distribution curve,respectively.D 1140 Test Method for Amount of Material in Soils FinerThan the No. 200 (75-µm) SieveD 2216 Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by MassD 2217 Practice for Wet Preparation of Soil Samples forParticle-Size Analysis and Determination of Soil ConstantsD 2488 Practice for Description and Identification of Soils(Visual-Manual Procedure)D 3740 Practice for Minimum Requirements for AgenciesEngaged in the Testing and/or Inspection of Soil and Rockas Used in Engineering Design and ConstructionD 4083 Practice for Description of Frozen Soils (VisualManual Procedure)D 4318 Test Methods for Liquid Limit, Plastic Limit, andPlasticity Index of SoilsD 4427 Classification of Peat Samples by Laboratory TestingD 6913 Test Methods for Particle-Size Distribution (Gradation) of Soils Using Sieve AnalysisE 11 Specification for Wire Cloth and Sieves for TestingPurposes3. Terminology3.1 Definitions—Except as listed below, all definitions arein accordance with Terminology D 653.NOTE 4—For particles retained on a 3-in. (75-mm) U.S. standard sieve,the following definitions are suggested:Cobbles—particles of rock that will pass a 12-in. (300-mm) squareopening and be retained on a 3-in. (75-mm) U.S. standard sieve, andBoulders—particles of rock that will not pass a 12-in. (300-mm) squareopening.3.1.1 clay—soil passing a No. 200 (75-µm) U.S. standardsieve that can be made to exhibit plasticity (putty-like properties) within a range of water contents and that exhibitsconsiderable strength when air dry. For classification, a clay isa fine-grained soil, or the fine-grained portion of a soil, with aplasticity index equal to or greater than 4, and the plot ofplasticity index versus liquid limit falls on or above the “A”line.3.1.2 gravel—particles of rock that will pass a 3-in. (75mm) sieve and be retained on a No. 4 (4.75-mm) U.S. standardsieve with the following subdivisions:Coarse—passes 3-in. (75-mm) sieve and retained on 3 4-in.(19-mm) sieve, and4. Summary4.1 As illustrated in Table 1, this classification systemidentifies three major soil divisions: coarse-grained soils,fine-grained soils, and highly organic soils. These three divisions are further subdivided into a total of 15 basic soil groups.TABLE 1 Soil Classification ChartCriteria for Assigning Group Symbols and Group Names Using Laboratory TestsACOARSE-GRAINEDGravelsClean GravelsSOILSMore than 50 %More than 50 % ofLess than 5 % finesEretained on No.coarse fraction200 sieveretained on No. 4sieveGravels with Fines2Cu 4 and1 # Cc # 3CCu 4 and/or1 Cc 3CFines classify as MLor MHSoil ClassificationGroup SymbolGroup NameBGWWell-graded gravelDGPPoorly graded gravelDGMSilty gravelD,F,G

D 2487 – 06TABLE 1ContinuedCriteria for Assigning Group Symbols and Group Names Using Laboratory TestsAMore than 12 % finesEFines classify as CL orCHSandsClean SandsCu 6 and1 # Cc # 3C50 % or more ofLess than 5 % finesICu 6 and/orcoarse1 Cc 3Cfraction passes No. 4Sands with FinesFines classify as MLsieveor MHMore than 12 % finesIFines classify as CL orCHFINE-GRAINEDSilts and ClaysinorganicPI 7 and plots on orSOILSabove “A” lineJ50 % or more passesLiquid limit less thanPI 4 or plots belowthe No.50“A” lineJ200 seiveorganicLiquid limit ovendried 0.75Liquid limit not driedSilts and ClaysinorganicPI plots on or above“A” lineLiquid limit 50 or morePI plots below “A” lineorganicLiquid limit ovendried 0.75Liquid limit not driedHIGHLY ORGANICPrimarily organic matter, dark in color, and organic odorSOILSSoil ClassificationGroup SymbolGroup NameB,urule;1 GCClayey gravelD,F,GSWWell-graded sandHSPPoorly graded sandHSMSilty sandF,G,HSCClayey sandF,G,HCLLean clayK,L,MMLSiltK,L,MOLOrganic clayK,L,M,NOLCHOrganic siltK,L,M,OFat clayK,L,MMHOHElastic siltK,L,MOrganic clayK,L,M,PPTOrganic siltK,L,M,QPeatABased on the material passing the 3-in. (75-mm) sieve.If field sample contained cobbles or boulders, or both, add “with cobbles or boulders, or both” to group name.CCu D60/D10 Cc 5 D30!2 D10 3 D60DIf soil contains 15 % sand, add “with sand” to group name.EGravels with 5 to 12 % fines require dual symbols:GW-GM well-graded gravel with siltGW-GC well-graded gravel with clayGP-GM poorly graded gravel with siltGP-GC poorly graded gravel with clayFIf fines classify as CL-ML, use dual symbol GC-GM, or SC-SM.GIf fines are organic, add “with organic fines” to group name.HIf soil contains 15 % gravel, add “with gravel” to group name.ISands with 5 to 12 % fines require dual symbols:SW-SM well-graded sand with siltSW-SC well-graded sand with claySP-SM poorly graded sand with siltSP-SC poorly graded sand with clayJIf Atterberg limits plot in hatched area, soil is a CL-ML, silty clay.KIf soil contains 15 to 29 % plus No. 200, add “with sand” or “with gravel,” whichever is predominant.LIf soil contains 30 % plus No. 200, predominantly sand, add “sand ” to group name.MIf soil contains 30 % plus No. 200, predominantly gravel, add “gravelly” to group name.NPI 4 and plots on or above “A” line.OPI 4 or plots below“ A” line.PPI plots on or above “A” line.QPI plots below “A” line.B/5.3 The various groupings of this classification system havebeen devised to correlate in a general way with the engineeringbehavior of soils. This standard provides a useful first step inany field or laboratory investigation for geotechnical engineering purposes.5.4 This standard may also be used as an aid in trainingpersonnel in the use of Practice D 2488.5.5 This standard may be used in combination with PracticeD 4083 when working with frozen soils.4.2 Based on the results of visual observations and prescribed laboratory tests, a soil is catalogued according to thebasic soil groups, assigned a group symbol(s) and name, andthereby classified. The flow charts, Fig. 1 for fine-grained soils,and Fig. 3 for coarse-grained soils, can be used to assign theappropriate group symbol(s) and name.5. Significance and Use5.1 This standard classifies soils from any geographic location into categories representing the results of prescribedlaboratory tests to determine the particle-size characteristics,the liquid limit, and the plasticity index.5.2 The assigning of a group name and symbol(s) alongwith the descriptive information required in Practice D 2488can be used to describe a soil to aid in the evaluation of itssignificant properties for engineering use.NOTE 5—Notwithstanding the statements on precision and bias contained in this standard: The precision of this test method is dependent onthe competence of the personnel performing it and the suitability of theequipment and facilities used. Agencies that meet the criteria of PracticeD 3740 are generally considered capable of competent and objectivetesting. Users of this test method are cautioned that compliance withPractice D 3740 does not in itself assure reliable t