Unified Soil Classification System Training Part B - USCS using Laboratory Data

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

ASTM Standards Lab Data Classification is by ASTM D2487 Classification of Peat Samples, see ASTM D 4427 Field Classification is by D2488

Comparison of Particle Size Definitions

Activity 2 - Particle Size Comparisons

USCS Flow Chart - Activity 3

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

USCS Overview

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

USCS Overview

Activity 4 - Organic Soil Solve 4 samples

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 5 - Plasticity Chart

Activity 5 - Plasticity Chart Solve 4 samples

Activity 7 - Classify Fine-Grained Samples Assume 6 samples are not organic and classify by USCS

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

Coarse-grained Soils

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

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

For 7 samples, fill out Activity

Additional Definitions To Classify Clean Coarse-Grained Soils, you must first plot grain-size curve and determine three parameters D10, D30, D60

Determining D10, D30, and D60 60 % finer D60, millimeters 30 10

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

Plot Curve from Data, compute CU Value Activity 9 Plot Curve from Data, compute CU Value

Plot Curve from Data, compute CC Value Activity 10 Plot Curve from Data, compute CC Value

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

Poorly Graded Sands and Gravels % Finer Particle Size Either Mostly One-Size Particle Gap graded Particle Size % Finer Or Gap- Graded

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

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 Review Example Soil

Use Flow Chart, Classify Soil Activity 13 Use Flow Chart, Classify Soil

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 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 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 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

Activity 16 - Problems

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

Activity 18 - Problem

Activity 20 - Review Questions

Activity 21 - Comprehensive Problems