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UNIFIED SOIL CLASSIFICATION SYSTEM <br /> . PRIMARY DIVISIONS SECONDARY DIVISIONS <br /> GRAVELS CLEAN GW Well graded gravels, gravel-sand mixtures, little or no fines <br /> y GRAVELS <br /> More than half of GP Poorly graded ravels ravel-sand mixtures, little or no fines <br /> � � (Less than 5% fines Y g g g <br /> Z coarse fraction is <br /> w larger than No 4 sieve GRAVEL <br /> 'u_ GM Silty gravels, gravel-sand-silt mixures, non-plastic fines <br /> ti <br /> Zo N WITH FINES GC Clayey gavels, gravel-sand-clay mixtures, plastic fines <br /> oC <br /> Vr G a SANDS CLEAN SW Well graded sands, gravelly sands, little or no fines <br /> SANDS <br /> W More than half ofLess than 5% fines SP Poorly graded sands or gravelly sands, little or no fines <br /> coarse fraction is <br /> to <br /> O smaller than SAND SM Silty sands, sand-silt mixtures, non-plastic fines <br /> c/U� No 4 sieve WITH FINES SC Clayey sands, sand-clay mixtures, plastic fines <br /> i.l SILTS AND CLAYS ML Inorganic silts and very fine sands, rock flour,silty or clayey fine sands or <br /> Sd u clayey silts with slight plasticity <br /> v Liquid limo is CL Inorganic clays of low to medium plasticity,gravelly clays,sandy clays, <br /> y silty clays,lean clays <br /> Q less than 50% <br /> W o N OL Organic silts and organic silty clays of low plasticty <br /> z � o <br /> 4z <br /> -4 SILTS AND CLAYS MH Inorganic silts, micaceous or diatomaceous fine sand or silty soils,elurie silt <br /> a ° <br /> s Liquid limit is CH Inorganic clays of high plasticity, far clays <br /> zogreater than 50% <br /> W f: OH Organic clays of medium to high plasticity, organic silts <br /> N <br /> HIGHLY ORGANIC SOILS Pt Peat and other highly organic soils <br /> DEFINITION OF TERMS <br /> U S STANDARD SERIES SIEVE CLEAR SQUARE SIEVE OPENINGS <br /> 200 40 10 4 314" 3" 12" <br /> SAND GRAVEL <br /> SILTS AND CLAYS COBBLES BOULDERS <br /> FINE MEDIUM COARSE FINE COARSE <br /> GRAIN SIZES <br /> Std Pen 2"ID SS SILTS & CLAYS POCKET Std Pen 2"ID SS <br /> SANDS & GRAVELS <br /> BLOWSIFTi BLOWS/FT PENETROMETER' BLOWSIFTi BLOWS/FT <br /> VERY LOOSE 0 - 4 0 - 7 VERY SOFT 0 - 250 0 - 2 0 - 3 <br /> LOOSE 4 - 10 7 - 16 SOFT 250 - 500 2 - 4 3 - 6 <br /> MEDIUM DENSE 10 - 30 16 - 50 FIRM 500 - 1,000 4 - 8 6 - 13 <br /> DENSE 30 - 50 50 - 83 STIFF 1,000 - 2,000 8 - 16 13 - 26 <br /> VERY DENSE OVER 50 OVER 83 VERY STIFF 2,000 - 4,000 16 - 32 26 - 53 <br /> HARD OVER 4,000 OVER 32 OVER 53 <br />• RELATIVE DENSITY Correction <br /> CONSISTENCY Factor - 6 <br /> i <br /> Number of blows of 140-pound hammer falling 30 inches to drive a 2-inch O D (1-318 inch I D) split spoon (ASTM D-1586) <br /> z <br /> Unconfined compressive strength in tons/sq R as determined by laboratory testing or approximated by the standard <br /> penetration test(ASTM D-1586),pocket penetrometer,torvane,or visual observation <br />