Unified Soil Classification Unified Soil Classification System TrainingSystem Training

Part B - USCS using Laboratory DataPart B - USCS using Laboratory Data

Comparison of Particle Size Comparison of Particle Size DefinitionsDefinitions USDA

cobblessandclay gravel

3”2 .05 mm # 4

silt

USCS

cobblessandfines gravel

.074 mm # 4 3”

# 200

ASTM StandardsASTM Standards

Lab Data Classification is byLab Data Classification is by

ASTM D2487 ASTM D2487

Classification of Peat Samples, see Classification of Peat Samples, see

ASTM D 4427ASTM D 4427

Field Classification is by D2488Field Classification is by D2488

Comparison of Particle Size Comparison of Particle Size DefinitionsDefinitions

Activity 2Activity 2 - Particle Size Comparisons - Particle Size Comparisons

USCS Flow Chart - Activity 3USCS Flow Chart - Activity 3

Flow Chart OverviewFlow Chart Overview

Two Broad CategoriesTwo Broad Categories– Fine-Grained - 50% or more finer than the Fine-Grained - 50% or more finer than the

# 200 sieve# 200 sieve

– Coarse-Grained - Less than 50% finer than Coarse-Grained - Less than 50% finer than the # 200 sievethe # 200 sieve

USCS OverviewUSCS Overview

F in e -G ra in ed

S o ils

5 0 % or M o rep a sse s the# 2 00 sie ve

C o a rse-G ra in ed

S o ils

L e ss tha n 5 0 %is f ine r th an

th e # 2 0 0 s ie ve

M e a su re %F in e r th an

# 20 0 S ie ve

Flow Chart OverviewFlow Chart Overview

Fine-Grained SoilsFine-Grained Soils– Organic ( LL ratio < 0.75 )Organic ( LL ratio < 0.75 )

– Inorganic (no odor and LL ratio not < 0.75)Inorganic (no odor and LL ratio not < 0.75)

– Classify by LL, PIClassify by LL, PI

– Modifiers are H or L for LL value, C or M Modifiers are H or L for LL value, C or M for plasticity and O for organicfor plasticity and O for organic

USCS OverviewUSCS Overview

O L

A ir-d ry LLis < 50

O H

A ir-D ry L Lis = o r > 50

O rg a n icS o ils

R a tio o f O ve n -d ryto A ir-d ryL L V a lu esis < 0 .75

C la ss ify b yP lo tt in g L L &

P I o n P la s tic ityC h a rt

In o rga n icS o ils

R a tio o f O ve n -d ryto A ir-d ryL L V a lu esis > 0 .75

D e te rm ineW h eth erO rg a n icO r n o t

Activity 4 - Organic Soil Activity 4 - Organic Soil

Solve 4 samplesSolve 4 samples

Abbreviations Fine-GrainedAbbreviations Fine-Grained

H - High LL ( H - High LL ( >> 50 ) 50 ) L - Low LL ( < 50 ) L - Low LL ( < 50 ) C - Plastic FinesC - Plastic Fines M - Nonplastic or slightly plastic M - Nonplastic or slightly plastic

finesfines O - OrganicO - Organic Pt - PeatPt - Peat

Activity 5 - Plasticity ChartActivity 5 - Plasticity ChartUnified Soil Classification System Plasticity Chart

0

10

20

30

40

50

60

0 10 20 30 40 50 60 70 80 90 100

LIQUID LIMIT

PL

AS

TIC

ITY

IND

EX CH

CL

ML

MH

CL-ML

Activity 5 - Plasticity Chart Activity 5 - Plasticity Chart

Solve 4 samplesSolve 4 samples

Activity 7 - Classify Fine-Activity 7 - Classify Fine-Grained Samples Grained Samples

Assume 6 samples are Assume 6 samples are not not

organicorganic and classify by USCS and classify by USCS

Flow Chart OverviewFlow Chart Overview

Coarse-Grained Soils - 3 GroupsCoarse-Grained Soils - 3 Groups

– Clean - Less than 5 % FinesClean - Less than 5 % Fines

– Dirty - More than 12 % FinesDirty - More than 12 % Fines

– Dual - From 5% to 12% Fines, Dual - From 5% to 12% Fines,

inclusiveinclusive

Coarse-grained SoilsCoarse-grained Soils

C le anC o a rse-G ra in ed

L e ss tha n 5 %fin er th an

# 2 00 sie ve

D u a lC o a rse-G ra in ed

F ro m 5 % to 1 2 %(in c lu s ive )f in e r th an

# 2 00 sie ve

D irt yC o a rse-G ra in ed

M o re tha n 1 2 %fin er th an

# 2 00 sie ve

L e ss tha n 5 0 %is f ine r th an# 2 00 sie ve

Abbreviations Sands and GravelsAbbreviations Sands and Gravels

G - GravelG - Gravel

S - SandS - Sand

P - Poorly GradedP - Poorly Graded

W - Well GradedW - Well Graded

Sieve AnalysesSieve Analyses

% fines = % finer than # 200 sieve

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

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

Percent Particle CategoriesPercent Particle Categories

To compute % Gravel subtract % finer To compute % Gravel subtract % finer

than # 4 from % finer than 3”than # 4 from % finer than 3”

To compute % Sand subtract % finer To compute % Sand subtract % finer

than # 200 from % finer than # 4than # 200 from % finer than # 4

Percent Fines is % finer than # 200Percent Fines is % finer than # 200

Activity 8Activity 8

For 7 samples, fill out ActivityFor 7 samples, fill out Activity

Additional DefinitionsAdditional Definitions

To Classify Clean Coarse-Grained Soils, To Classify Clean Coarse-Grained Soils,

you must first plot grain-size curve and you must first plot grain-size curve and

determine three parametersdetermine three parameters

DD1010, D, D3030, D, D6060

Determining DDetermining D1010, D, D3030, and D, and D6060

D10, millimeters

10

% f

iner

D30, millimeters

30

D60, millimeters

60

Computing CU and CCComputing CU and CC

10

60

D

DCU

6010

230

DD

DCC

Coefficient of Uniformity

Coefficient of Curvature

High Values Indicate Well-Graded Soil

Values Between 1-3 Indicate Well-Graded Soil

Activity 9Activity 9

Plot Curve from Data, compute Plot Curve from Data, compute

CU ValueCU Value

Activity 10Activity 10

Plot Curve from Data, compute Plot Curve from Data, compute

CC ValueCC Value

CCharacterizing Clean haracterizing Clean Sands and GravelsSands and Gravels

Particle SizeParticle Size

% F

iner

% F

iner Well gradedWell graded

Clean Well Graded Sands and Gravels have Clean Well Graded Sands and Gravels have less than 5 % fines and a wide range of less than 5 % fines and a wide range of particle sizes that are equally distributedparticle sizes that are equally distributed

Poorly GradedPoorly Graded Sands and GravelsSands and Gravels

Poorly gradedPoorly graded

% F

iner

% F

iner

Particle SizeParticle Size

Either Mostly One-Size Particle

Gap gradedGap graded

Particle SizeParticle Size

% F

iner

% F

iner

Or Gap-

Graded

Clean, Well/Poorly Graded Clean, Well/Poorly Graded DefinitionsDefinitions

SandsSands– less than 5 % less than 5 %

finesfines

– CU > 6CU > 6

– CC = 1-3CC = 1-3

GravelsGravels– less than 5 % less than 5 %

fines fines

– CU > 4CU > 4

– CC = 1-3CC = 1-3

Activity 11 - ProblemsActivity 11 - Problems

1. Verify % Fines - Coarse-Grained/Clean1. Verify % Fines - Coarse-Grained/Clean

2. Compute % Gravel and % Sand2. Compute % Gravel and % Sand

3. Note which predominates3. Note which predominates

4. Using provided CU and CC, Determine 4. Using provided CU and CC, Determine whether poorly or well gradedwhether poorly or well graded

5. Determine Correct USCS classification5. Determine Correct USCS classification

Activity 12Activity 12

Review Example SoilReview Example Soil

Activity 13Activity 13

Use Flow Chart, Classify SoilUse Flow Chart, Classify Soil

Activity 14 Summary of Classifications of Activity 14 Summary of Classifications of Coarse-Grained SoilsCoarse-Grained Soils

Clean Sands and Gravels (< 5% fines)Clean Sands and Gravels (< 5% fines)– Clean Poorly Graded Gravels GPClean Poorly Graded Gravels GP

– Clean Well Graded Gravels GWClean Well Graded Gravels GW

– Clean Poorly Graded Sands SPClean Poorly Graded Sands SP

– Clean Well Graded Sands SWClean Well Graded Sands SW

Dirty Coarse-Grained SoilsDirty Coarse-Grained Soils

If a sample has less than 50 % FinesIf a sample has less than 50 % Fines

And it has more than 12 % Fines, it is a And it has more than 12 % Fines, it is a

Dirty Coarse-Grained SoilDirty Coarse-Grained Soil

To Classify, follow the flow chart and To Classify, follow the flow chart and

the following stepsthe following steps

Dirty Coarse-Grained SoilDirty Coarse-Grained Soil

Determine whether there is a greater % Determine whether there is a greater %

of Sand or Gravelof Sand or Gravel– % G = % finer 3” minus # 4% G = % finer 3” minus # 4

– % S = % finer # 4 minus # 200% S = % finer # 4 minus # 200

Determine where minus # 40 fines plot Determine where minus # 40 fines plot

on plasticity charton plasticity chart

Dirty Sands and GravelsDirty Sands and Gravels

SC - Fines Plot Above A-LineSC - Fines Plot Above A-Line SM - Fines Plot Below A-LineSM - Fines Plot Below A-Line SC-SM - Fines Plot in Hatched ZoneSC-SM - Fines Plot in Hatched Zone

GC - Fines Plot Above A-LineGC - Fines Plot Above A-Line GM - Fines Plot Below A-LineGM - Fines Plot Below A-Line GC-GM - Fines Plot in Hatched ZoneGC-GM - Fines Plot in Hatched Zone

Sands

Gravels

Activity 16 - ProblemsActivity 16 - Problems

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

Activity 18 - ProblemActivity 18 - Problem

Activity 20 - Review QuestionsActivity 20 - Review Questions

Activity 21 - Comprehensive Activity 21 - Comprehensive ProblemsProblems