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Unified Soil Classification System Training






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Unified Soil Classification System Training. Part B - USCS using Laboratory Data. USDA. cobbles. clay. silt. sand. gravel. 2 m. # 4. 3”. .05 mm. USCS. cobbles. fines. sand. gravel. # 4. 3”. .074 mm. Comparison of Particle Size Definitions. # 200. ASTM Standards .
Unified Soil Classification System Training

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Slide 1

Unified Soil Classification System Training

Part B - USCS using Laboratory Data

Slide 2

USDA

cobbles

clay

silt

sand

gravel

2 m

# 4

3”

.05 mm

USCS

cobbles

fines

sand

gravel

# 4

3”

.074 mm

Comparison of Particle Size Definitions

# 200

Slide 3

ASTM Standards

  • Lab Data Classification is byASTM D2487

  • Classification of Peat Samples, see ASTM D 4427

  • Field Classification is by D2488

Slide 4

Comparison of Particle Size Definitions

Slide 5

Activity 2 - Particle Size Comparisons

Slide 6

USCS Flow Chart - Activity 3

Slide 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

Slide 8

USCS Overview

Slide 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

Slide 10

USCS Overview

Slide 11

Activity 4 - Organic Soil

Solve 4 samples

Slide 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

Slide 13

Activity 5 - Plasticity Chart

Slide 14

Activity 5 - Plasticity Chart

Solve 4 samples

Slide 15

Activity 7 - Classify Fine-Grained Samples

Assume 6 samples are not organic and classify by USCS

Slide 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

Slide 17

Coarse-grained Soils

Slide 18

Abbreviations Sands and Gravels

  • G - Gravel

  • S - Sand

  • P - Poorly Graded

  • W - Well Graded

Slide 19

% gravel = % finer 3”minus % finer # 4

% sand = % finer # 4 minus % finer # 200

% fines = % finer than # 200 sieve

Sieve Analyses

Slide 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

Slide 21

Activity 8

For 7 samples, fill out Activity

Slide 22

Additional Definitions

  • To Classify Clean Coarse-Grained Soils, you must first plot grain-size curve and determine three parameters

    D10, D30, D60

Slide 23

Determining D10, D30, and D60

60

% finer

D60, millimeters

30

10

D30, millimeters

D10, millimeters

Slide 24

Computing CU and CC

Coefficient of Uniformity

High Values Indicate Well-Graded Soil

Coefficient of Curvature

Values Between 1-3 Indicate Well-Graded Soil

Slide 25

Activity 9

Plot Curve from Data, compute CU Value

Slide 26

Activity 10

Plot Curve from Data, compute CC Value

Slide 27

Well graded

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

% Finer

Particle Size

Slide 28

Either Mostly One-Size Particle

Or Gap-

Graded

% Finer

% Finer

Poorly graded

Gap graded

Particle Size

Particle Size

Poorly GradedSands and Gravels

Slide 29

Sands

less than 5 % fines

CU > 6

CC = 1-3

Gravels

less than 5 % fines

CU > 4

CC = 1-3

Clean, Well/Poorly Graded Definitions

Slide 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

Slide 31

Activity 12

Review Example Soil

Slide 32

Activity 13

Use Flow Chart, Classify Soil

Slide 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

Slide 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

Slide 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

Slide 36

Sands

Gravels

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

Slide 37

Activity 16 - Problems

Slide 38

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

Slide 39

Activity 18 - Problem

Slide 40

Activity 20 - Review Questions

Slide 41

Activity 21 - Comprehensive Problems


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