1. Unified Soil Classification System Training
Part B - USCS using Laboratory Data

2. Comparison of Particle Size Definitions
USDA
cobbles
sand
clay
gravel 3”
2 m
.05 mm
# 4
silt
USCS
cobbles
sand
fines
gravel
.074 mm
# 4 3”
# 200

3. ASTM Standards Lab Data Classification is by ASTM D2487
Classification of Peat Samples, see ASTM D 4427
Field Classification is by D2488

4. Comparison of Particle Size Definitions

5. Activity 2 - Particle Size Comparisons

6. USCS Flow Chart - Activity 3

7. Flow Chart Overview Two Broad Categories
Fine-Grained - 50% or more finer than the # 200 sieve
Coarse-Grained - Less than 50% finer than the # 200 sieve

8. USCS Overview

9. Flow Chart Overview Fine-Grained Soils Organic ( LL ratio < 0.75 )
Inorganic (no odor and LL ratio not < 0.75)
Classify by LL, PI
Modifiers are H or L for LL value, C or M for plasticity and O for organic

10. USCS Overview

11. Activity 4 - Organic Soil
Solve 4 samples

12. Abbreviations Fine-Grained
H - High LL ( > 50 )
L - Low LL ( < 50 )
C - Plastic Fines
M - Nonplastic or slightly plastic fines
O - Organic
Pt - Peat

13. Activity 5 - Plasticity Chart

14. Activity 5 - Plasticity Chart
Solve 4 samples

15. Activity 7 - Classify Fine-Grained Samples
Assume 6 samples are not organic and classify by USCS

16. Flow Chart Overview Coarse-Grained Soils - 3 Groups
Clean - Less than 5 % Fines
Dirty - More than 12 % Fines
Dual - From 5% to 12% Fines, inclusive

17. Coarse-grained Soils

18. Abbreviations Sands and Gravels
G - Gravel
S - Sand
P - Poorly Graded
W - Well Graded

19. Sieve Analyses % gravel = % finer 3”minus % finer # 4
% sand = % finer # 4 minus % finer # 200
% fines = % finer than # 200 sieve

20. Percent Particle Categories
To compute % Gravel subtract % finer than # 4 from % finer than 3”
To compute % Sand subtract % finer than # 200 from % finer than # 4
Percent Fines is % finer than # 200

21. For 7 samples, fill out Activity

22. Additional Definitions
To Classify Clean Coarse-Grained Soils, you must first plot grain-size curve and determine three parameters
D10, D30, D60

23. Determining D10, D30, and D60 60 % finer D60, millimeters 30 10

24. Coefficient of Uniformity
Computing CU and CC
Coefficient of Uniformity
High Values Indicate Well-Graded Soil
Coefficient of Curvature
Values Between 1-3 Indicate Well-Graded Soil

25. Plot Curve from Data, compute CU Value
Activity 9
Plot Curve from Data, compute CU Value

26. Plot Curve from Data, compute CC Value
Activity 10
Plot Curve from Data, compute CC Value

27. Characterizing Clean Sands and Gravels
Clean Well Graded Sands and Gravels have less than 5 % fines and a wide range of particle sizes that are equally distributed
Well graded
% Finer
Particle Size

28. Poorly Graded Sands and Gravels
% Finer
Particle Size
Either Mostly One-Size Particle
Gap graded
Particle Size
% Finer
Or Gap-
Graded

29. Clean, Well/Poorly Graded Definitions
Sands
less than 5 % fines
CU > 6
CC = 1-3
Gravels
less than 5 % fines
CU > 4
CC = 1-3

30. Activity 11 - Problems 1. Verify % Fines - Coarse-Grained/Clean
2. Compute % Gravel and % Sand
3. Note which predominates
4. Using provided CU and CC, Determine whether poorly or well graded
5. Determine Correct USCS classification

31. Activity 12
Review Example Soil

32. Use Flow Chart, Classify Soil
Activity 13
Use Flow Chart, Classify Soil

33. Activity 14 Summary of Classifications of Coarse-Grained Soils
Clean Sands and Gravels (< 5% fines)
Clean Poorly Graded Gravels GP
Clean Well Graded Gravels GW
Clean Poorly Graded Sands SP
Clean Well Graded Sands SW

34. Dirty Coarse-Grained Soils
If a sample has less than 50 % Fines
And it has more than 12 % Fines, it is a Dirty Coarse-Grained Soil
To Classify, follow the flow chart and the following steps

35. Dirty Coarse-Grained Soil
Determine whether there is a greater % of Sand or Gravel
% G = % finer 3” minus # 4
% S = % finer # 4 minus # 200
Determine where minus # 40 fines plot on plasticity chart

36. Dirty Sands and Gravels
SC - Fines Plot Above A-Line
SM - Fines Plot Below A-Line
SC-SM - Fines Plot in Hatched Zone
GC - Fines Plot Above A-Line
GM - Fines Plot Below A-Line
GC-GM - Fines Plot in Hatched Zone
Gravels

37. Activity 16 - Problems

38. Activity 17 - Example of Classifying Dual-Classification Coarse-Grained Soil

39. Activity 18 - Problem

40. Activity 20 - Review Questions

41. Activity 21 - Comprehensive Problems