USCS (ASTM D2487) & AASHTO (M 145) Classification ā Enter gradation & Atterberg limits, get group symbol, name, and engineering properties
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Soil Classifier
Unified Soil Classification System (USCS) and AASHTO M 145. Input sieve analysis and Atterberg limits for instant classification with engineering correlations.
š Sieve Analysis
% passing
% passing
% passing
% passing
% passing
% passing
% passing
% passing
% passing
% passing
š§Ŗ Atterberg Limits
%
%
š·ļø USCS Classification Result
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Group Symbol
--
Group Name
--
š
% Gravel
--%
šļø
% Sand
--%
š§
% Fines
--%
š
Cu
--
š
Cc
--
š“
LL
--
šµ
PL
--
š£
PI
--
š Gradation Curve
šļø Typical Engineering Properties
ā Suitability
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Enter Gradation & Atterberg
Input sieve analysis and LL/PL, then click Classify USCS.
š AASHTO M 145 Inputs
%
%
%
%
%
š·ļø AASHTO Classification Result
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Group
--
Group Index
--
š
% Gravel
--%
šļø
% Sand
--%
š§
% Silt/Clay
--%
š AASHTO Group Descriptions
š£ļø Pavement Suitability
š GI Formula
GI = (F-35)[0.2+0.005(LL-40)] + 0.01(F-15)(PI-10) where F=% passing #200. GI ā„ 0. Higher = poorer subgrade.
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Enter AASHTO Parameters
āļø USCS ā AASHTO Comparison
USCS Group
USCS Name
AASHTO Group
Typical GI
Description
š Key Differences
USCS (ASTM D2487):
- Based on particle size distribution AND plasticity
- 15 groups: GW, GP, GM, GC, SW, SP, SM, SC, ML, CL, OL, MH, CH, OH, Pt
- Well-graded vs poorly-graded distinction for coarse soils
- Plasticity chart (A-line) for fine soils
AASHTO M 145:
- Developed for highway subgrade evaluation
- 7 main groups: A-1 through A-7 (+ A-8 for peat)
- Subgroups: a (granular) vs b (silt-clay)
- Group Index (GI) quantifies quality within group
- GI = 0 = best, GI > 20 = very poor
Correlation Rules (approximate):
- GW/GP ā A-1-a / A-1-b
- GM/GC ā A-2-4 / A-2-5 / A-2-6 / A-2-7
- SW/SP ā A-3 / A-1-b
- SM/SC ā A-2-4 / A-2-6
- ML/CL ā A-4 / A-6
- MH/CH ā A-5 / A-7
š Engineering Properties by Classification
Group
Permeability
Compressibility
Shear Strength
Compaction
CBR Range
Subgrade Rating
š Plasticity Chart (A-Line)
š Key Equations
Coefficient of Uniformity: Cu = Dāā / Dāā
Coefficient of Curvature: Cc = (Dāā)Ā² / (Dāā Ć Dāā)
Well-graded gravel (GW): Cu ā„ 4 AND 1 ā¤ Cc ā¤ 3
Well-graded sand (SW): Cu ā„ 6 AND 1 ā¤ Cc ā¤ 3
A-Line: PI = 0.73 Ć (LL - 20)
Above A-line: Clay (C) | Below A-line: Silt (M) or Organic (O)
Group Index (AASHTO):
GI = (F-35)[0.2+0.005(LL-40)] + 0.01(F-15)(PI-10)
F = % passing #200 sieve (0-100)
LL = Liquid Limit, PI = Plasticity Index
GI ā„ 0 (negative set to 0)