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ASTM Designation D-2487 and D 2488 (Unified Soil Classification System) <br />Group <br />Major Divisions Typical Names Classification Criteria <br />Symbols <br />Clean Gravels <br />Well –graded gravels <br />50% or more of coarse fraction <br /> = <br />CD / D <br /> greater than 4. <br /> requiring use of duel symbols. <br />and gravel-sand <br />u6010 <br />GW <br />2 <br />mixtures, little or no <br />C = (D) / (D x D) <br /> between 1 & 3. <br />z301060 <br />eve: Borderline Classification <br />fines. <br />retained on No. 4 sieve. <br />Poorly graded gravels <br />and gravel-sand <br />GP Less than 5% passing No. 200 Sieve: GW, GP, SW, SP <br /> Sieve: GM, GC, SM, SC Not meeting both criteria for GW materials. <br />mixtures, little or no <br />fines. <br />Classification on basis of percentage of fines. <br />Gravels with <br />Atterberg limits <br />Silty gravels, gravel- <br />Atterberg limits plotting <br />GM <br />below “A” line, or <br />sand-silt mixtures. <br />Gravels <br />in hatched area are <br />More than 50% retained on No. 200 sieve * <br />P.I. less than 4. <br />borderline <br />Fines <br />Atterberg limits <br />classifications requiring <br />Clayey gravels, gravel- <br />GC <br />above “A” line with <br />use of dual symbols. <br />sand-clay mixtures. <br />P.I. greater than 7. <br />From 5% to 12% passing No. 200 Si <br />Clean Sands <br />Well-graded sands and <br /> = <br />CD / D <br />greater than 6. <br />u6010 <br />SW <br />gravelly sands, little or More than 12% passing No. 200 <br />fraction passes No 4 sieve. <br />2 <br />C = (D) / (D x D) <br />between 1 & 3. <br />More than 50% of coarse <br />z301060 <br />no fines. <br />Course Grained Soils <br />Poorly-graded sands <br />SP <br />Not meeting both criteria for SW materials. <br />and gravelly sands, little <br />or no fines. <br />Atterberg limits <br />Sands with <br />Silty sands, sand-silt <br />Atterberg limits plotting <br />below “A” line, or <br />SM <br />mixtures. <br />in hatched area are <br />P.I. less than 4. <br />Sands <br />borderline <br />Fines <br />Atterberg limits <br />classifications requiring <br />Clayey sands, sand- <br />above “A” line with <br />SC <br />use of dual symbols. <br />clay mixtures. <br />P.I. greater than 7. <br />Inorganic silts, very fine <br />Liquid Limit of 50% or <br />Plasticity Index Chart <br />ML <br />sands, rock flour, silty <br />or clayey fine sands. <br />60 <br />Silts and Clays <br />Inorganic clays of low to <br />medium plasticity, <br />Chart for classification of fine grained soils <br />50 <br />CL <br />and the fin fraction of coarse grained soils. <br />gravelly clays, sandy <br />CH Soils <br />clays, silty clays, lean <br />Atterberg Limits plotting in hatched area are <br />clays. <br />borderline classifications requiring use of dual <br />40 <br />less <br />symbols. <br />Organic silts and <br />OL <br />organic silty clays of <br />30 <br />low plasticity. <br />More than 50% passes No. 200 sieve * <br />Liquid Limit greater than Inorganic silts, <br />CL Soils <br />"A" Line <br />micaceous or <br />20 <br />MH <br />diatomaceous fine <br />sands or silts, elastic <br />Silts and Clays <br />OH & MH Soils <br />10 <br />silts. <br />CL-ML Soils <br />Inorganic clays of high <br />OL & ML Soils <br />CH <br />0 <br />plasticity, fat clays. <br />Fine Grained Soils <br />0102030405060708090100 <br />50%. <br />Liquid Limit <br />Organic clays of <br />OH <br />medium to high <br />plasticity. <br />Organic <br />Highly <br />Soils <br />Peat, muck and other <br />Pt <br />highly organic soils. <br />12 <br /> <br />