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Unified Soil Classification System Training


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.

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Unified Soil Classification System Training

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Unified soil classification system training l.jpg

Unified Soil Classification System Training

Part B - USCS using Laboratory Data


Comparison of particle size definitions l.jpg

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 l.jpg

ASTM Standards

  • Lab Data Classification is byASTM D2487

  • Classification of Peat Samples, see ASTM D 4427

  • Field Classification is by D2488


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Comparison of Particle Size Definitions


Activity 2 particle size comparisons l.jpg

Activity 2 - Particle Size Comparisons


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USCS Flow Chart - Activity 3


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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


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USCS Overview


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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


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USCS Overview


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Activity 4 - Organic Soil

Solve 4 samples


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Abbreviations Fine-Grained

  • H - High LL ( > 50 )

  • L - Low LL ( < 50 )

  • C - Plastic Fines

  • M - Nonplastic or slightly plastic fines

  • O - Organic

  • Pt - Peat


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Activity 5 - Plasticity Chart


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Activity 5 - Plasticity Chart

Solve 4 samples


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Activity 7 - Classify Fine-Grained Samples

Assume 6 samples are not organic and classify by USCS


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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


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Coarse-grained Soils


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Abbreviations Sands and Gravels

  • G - Gravel

  • S - Sand

  • P - Poorly Graded

  • W - Well Graded


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

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

% fines = % finer than # 200 sieve

Sieve Analyses


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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


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Activity 8

For 7 samples, fill out Activity


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Additional Definitions

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

    D10, D30, D60


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Determining D10, D30, and D60

60

% finer

D60, millimeters

30

10

D30, millimeters

D10, millimeters


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Computing CU and CC

Coefficient of Uniformity

High Values Indicate Well-Graded Soil

Coefficient of Curvature

Values Between 1-3 Indicate Well-Graded Soil


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Activity 9

Plot Curve from Data, compute CU Value


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Activity 10

Plot Curve from Data, compute CC Value


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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


Poorly graded sands and gravels l.jpg

Either Mostly One-Size Particle

Or Gap-

Graded

% Finer

% Finer

Poorly graded

Gap graded

Particle Size

Particle Size

Poorly GradedSands and Gravels


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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


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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


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Activity 12

Review Example Soil


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Activity 13

Use Flow Chart, Classify Soil


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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


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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


Dirty coarse grained soil l.jpg

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


Dirty sands and gravels l.jpg

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


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Activity 16 - Problems


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


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Activity 18 - Problem


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Activity 20 - Review Questions


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Activity 21 - Comprehensive Problems