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**Unified Soil Classification System Training**

Part B - USCS using Laboratory Data

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**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

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**ASTM Standards Lab Data Classification is by ASTM D2487**

Classification of Peat Samples, see ASTM D 4427 Field Classification is by D2488

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**Comparison of Particle Size Definitions**

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**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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**Sieve Analyses % gravel = % finer 3”minus % finer # 4**

% sand = % finer # 4 minus % finer # 200 % fines = % finer than # 200 sieve

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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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**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**

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**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

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**Plot Curve from Data, compute CU Value**

Activity 9 Plot Curve from Data, compute CU Value

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**Plot Curve from Data, compute CC Value**

Activity 10 Plot Curve from Data, compute CC Value

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**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

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**Poorly Graded Sands and Gravels**

% Finer Particle Size Either Mostly One-Size Particle Gap graded Particle Size % Finer Or Gap- Graded

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**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

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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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**Use Flow Chart, Classify Soil**

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

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**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

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**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

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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**

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