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SOIL DESCRIPTION AND CLASSIFICATION GUIDELINES Particle-Size Classification ASTM/USCS AASHTO COMPONENT size range sieve size range size range sieve size range Cobbles > 75 mm greater than 3 inches > 75 mm greater than 3 inches Gravel 75 mm – 4.75 mm 3 inches to No. 4 sieve 75 mm – 2.00 mm 3 inches to No. 10 sieve Coarse 75 mm – 19.0 mm 3 inches to 3/4-inch sieve - - Fine 19.0 mm – 4.75 mm 3/4-inch to No. 4 sieve - - Sand 4.75 mm – 0.075 mm No. 4 to No. 200 sieve 2.00 mm – 0.075 mm No. 10 to No. 200 sieve Coarse 4.75 mm – 2.00 mm No. 4 to No. 10 sieve 2.00 mm – 0.425 mm No. 10 to No. 40 sieve Medium 2.00 mm – 0.425 mm No. 10 to No. 40 sieve - - Fine 0.425 mm – 0.075 mm No. 40 to No. 200 sieve 0.425 mm – 0.075 mm No. 40 to No. 200 sieve Fines (Silt and Clay) < 0.075 mm Passing No. 200 sieve < 0.075 mm Passing No. 200 sieve Consistency for Cohesive Soil CONSISTENCY SPT N-VALUE (BLOWS PER FOOT) POCKET PENETROMETER (UNCONFINED COMPRESSIVE STRENGTH, tsf) Very Soft Soft Medium Stiff Stiff Very Stiff Hard Very Hard 2 2 to 4 4 to 8 8 to 15 15 to 30 30 to 60 greater than 60 less than 0.25 0.25 to 0.50 0.50 to 1.0 1.0 to 2.0 2.0 to 4.0 greater than 4.0 - Relative Density for Granular Soil RELATIVE DENSITY SPT N-VALUE (BLOWS PER FOOT) Very Loose Loose Medium Dense Dense Very Dense 0 to 4 4 to 10 10 to 30 30 to 50 more than 50 Moisture Designations TERM FIELD IDENTIFICATION Dry No moisture. Dusty or dry. Damp Some moisture. Cohesive soils are usually below plastic limit and are moldable. Moist Grains appear darkened, but no visible water is present. Cohesive soils will clump. Sand will bulk. Soils are often at or near plastic limit. Wet Visible water on larger grains. Sand and silt exhibit dilatancy. Cohesive soil can be readily remolded. Soil leaves wetness on the hand when squeezed. Soil is much wetter than optimum moisture content and is above plastic limit.