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CLASSIFICATION OF SOILS FOR ENGINEERING PURPOSES <br />ASTM Designation: D 2497 — 69 AND D 2488 — 69 <br />(Unified Soil Classification System) <br />Major divisions symbols <br />Typical names Classification criteria <br />a WelI- Waded gravels andw CU= 06o greater than 4; <br />GW gravel -sand mixtures, little o 2 <br />ij or no fines H C _= /030/ between 1 and 3 <br />8 m Z Dio xDGo <br />mPoorly graded gravels and <br />V U GP gravel -sand mixti•res, little Not meeting both criteria for GW <br />8 ? 15 <br />or no fines v°, <br />y U <br />4 C c y V 7 <br />e O ty gravels, gravel -sand- a U g' Atterberg limits below <br />Sil <br />0 GM `o tD tD c ''A" line or P.I. less Atterberglimitsplot- <br />y �.� £ silt mixtures m 3iO j than 4 ting in hatched area <br />g o r <br />0 0 m. are borderline classifi- <br />y m • • • cations requiring use <br />Atterber limits above <br />az > GC Clayeygravels, gravel- A•• line with P.I. of dual symbols <br />sand clay mixtures . . . greater than 7 <br />`o <br />rn <br />io <br />Well -Waded sands and gra- H i > CU = D60 greater than 6; <br />g 10 <br />SW fines sands, little or no [� m ^ Cz= Di0xoDso between 1 and <br />5i O xR"i y{. M <br />mPoorly graded sands and M Z Z o <br />y U SP gravelly sands, little or no a N R Not meeting both criteria for SW <br />$ • fines N 8 $ Z <br />15 Z <br />a �' Atterberg limits below <br />a Silty sands, sand -silt mix- jb A^ line or P.1. less <br />c SM tures ££ Atterberg limits plot- <br />8 than 4 ting in hatched area <br />are borderline classifi- <br />3 cations requiring use <br />Atterberg limits above of dual symbols <br />Sc Clayey sands, sand -clay •'A•' line with P.I. <br />mixtures greater than 7 <br />Inorganic silts, very fine Plasticity Chart <br />ML sands, rock flour, silty or 60 <br />clayey fine sands <br />N <br />� o <br />For classification of fine rained <br />soils and fine fraction of coarse - <br />Inorganic clays of low to 50 grained soils. <br />medium plasticity, gravelly Atterberg Limits plotting in CH <br />i _ CL clays, sandy clays• silty hatched area are borderline <br />N E clays, lean clays classifications requiring use of <br />N x 40 dual symbols. <br />e } Organic silts and organic Equation of A-line. <br />L OL silty clays of low plasticity PI 0.73 (LL -20) <br />30 <br />O U <br />Ali O .. <br />2 <br />N Inorganic silts, micaceous _A <br />Ln MH or diatomaceous fine sands rs <br />m or silts, elastic silts 20 <br />Qe £ <br />E d <br />L <br />Inorganic clays of high 10 <br />CH plasticity, fat clays <br />r 7 <br />E 4 <br />in = <br />V Organic clays of medium to 00 10 20 30 40 50 60 70 80 90 100 <br />a OH high plasticity <br />J <br />Liquid Limit <br />> U w Peat, muck and other hi 1 <br />E — Pt 47h V <br />organic soils *Based on the material passing the 3 in. (76 nen) sieve. <br />= 5 <br />= <br />6 <br />1170 -Ai <br />SE - <br />I <br />OH and <br />MH <br />,•P <br />� <br />CL <br />C <br />L - ML <br />ML and OL <br />II <br />