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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 .

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unified soil classification system training

Unified Soil Classification System Training

Part B - USCS using Laboratory Data

comparison of particle size definitions

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
ASTM Standards
  • Lab Data Classification is byASTM D2487
  • Classification of Peat Samples, see ASTM D 4427
  • Field Classification is by D2488
flow chart overview
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
flow chart overview9
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
abbreviations fine grained
Abbreviations Fine-Grained
  • H - High LL ( > 50 )
  • L - Low LL ( < 50 )
  • C - Plastic Fines
  • M - Nonplastic or slightly plastic fines
  • O - Organic
  • Pt - Peat
activity 7 classify fine grained samples

Activity 7 - Classify Fine-Grained Samples

Assume 6 samples are not organic and classify by USCS

flow chart overview16
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
abbreviations sands and gravels
Abbreviations Sands and Gravels
  • G - Gravel
  • S - Sand
  • P - Poorly Graded
  • W - Well Graded
sieve analyses

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

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

% fines = % finer than # 200 sieve

Sieve Analyses
percent particle categories
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
activity 8

Activity 8

For 7 samples, fill out Activity

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

D10, D30, D60

determining d 10 d 30 and d 60
Determining D10, D30, and D60

60

% finer

D60, millimeters

30

10

D30, millimeters

D10, millimeters

computing cu and cc
Computing CU and CC

Coefficient of Uniformity

High Values Indicate Well-Graded Soil

Coefficient of Curvature

Values Between 1-3 Indicate Well-Graded Soil

activity 9

Activity 9

Plot Curve from Data, compute CU Value

activity 10

Activity 10

Plot Curve from Data, compute CC Value

c haracterizing clean sands and gravels

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

Either Mostly One-Size Particle

Or Gap-

Graded

% Finer

% Finer

Poorly graded

Gap graded

Particle Size

Particle Size

Poorly GradedSands and Gravels
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

Clean, Well/Poorly Graded Definitions
activity 11 problems
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

activity 12

Activity 12

Review Example Soil

activity 13

Activity 13

Use Flow Chart, Classify Soil

activity 14 summary of classifications of coarse grained soils
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
dirty coarse grained soils
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
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

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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