Soils Classification Testing
An overview of test procedures to classify soils according to the Uniform Soil
Classification System (ASTM D 4287)
John S. Landwermeyer, P.E.
Austin, Texas
ARIAS & ASSOCIATES, INC.Geotechnical · Environmental · Materials Testing
Sieve Analysis (ASTM D 421)Representative SampleDry Sample to get total dry weight (Night 1)Wash sample over the #200 SieveDry Sample (Night 2)Dry shake through sievesWeigh contents of each sieve% Retained = Wt Retained ÷Total Wt
Sieve Analysis – Possible ErrorsUn-representative Sample
SegregationInsufficient wash of sample over the #200 Sieve: use brush!Over-loading of sieve nestTare weights, human errors
Atterberg Limits – Soil PrepRepresentative SampleSoak for up to 12 hours (“slaking time”) (Night 1)Remove aggregate on #10 sieve
Atterberg Limits – Soil PrepRepresentative SampleSoak for up to 12 hours (“slaking time”) (Night 1)Remove aggregate on #10 sieveMechanical mixing
Atterberg Limits – Soil PrepRepresentative SampleSoak for up to 12 hours (“slaking time”) (Night 1)Remove aggregate on #10 sieveMechanical mixingPour thru #40 sieve, into lined absorbent bowlAllow soil to dry to below the Liquid Limit (Night 2)
Atterberg Limits – Liquid LimitAdjust moisture to the Liquid LimitLL is reached when ½” of the grove closes after 25 blows
Atterberg Limits – Plastic LimitAdjust moisture to the Plastic LimitPL is reached when soil begins to break when rolled into 1/8” threads
Atterberg Limits – Plasticity Index PI = LL – PL
“Fat Clay” = LL > 50 (ASTM D 2487)“Lean Clay” = LL < 50 (ASTM D 2487)“Expansive” = PI > 20 Non-cohesive = non-plastic = sand, silt or gravel
Atterberg Limits – Possible ErrorsUn-representative sample or sub-sampleDry preparation (ASTM D 4318) pulverization of soils containing rock decreases PI