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

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Presentation on theme: "Unified Soil Classification System Training Part B - USCS using Laboratory Data."— Presentation transcript:

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

2 Comparison of Particle Size Definitions USDA cobbles sandclay gravel 3” 2 .05 mm # 4 silt USCS cobbles sandfines gravel.074 mm # 43” # 200

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

4 Comparison of Particle Size Definitions

5 Activity 2 - Particle Size Comparisons

6 USCS Flow Chart - Activity 3

7 Flow Chart Overview v Two Broad Categories –Fine-Grained - 50% or more finer than the # 200 sieve –Coarse-Grained - Less than 50% finer than the # 200 sieve

8 USCS Overview

9 Flow Chart Overview v 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

10 USCS Overview

11 Activity 4 - Organic Soil Solve 4 samples

12 Abbreviations Fine-Grained v H - High LL ( > 50 ) v L - Low LL ( < 50 ) v C - Plastic Fines v M - Nonplastic or slightly plastic fines v O - Organic v Pt - Peat

13 Activity 5 - Plasticity Chart

14 Solve 4 samples

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

16 Flow Chart Overview v Coarse-Grained Soils - 3 Groups –Clean - Less than 5 % Fines –Dirty - More than 12 % Fines –Dual - From 5% to 12% Fines, inclusive

17 Coarse-grained Soils

18 Abbreviations Sands and Gravels v G - Gravel v S - Sand v P - Poorly Graded v W - Well Graded

19 Sieve Analyses % fines = % finer than # 200 sieve % sand = % finer # 4 minus % finer # 200 % gravel = % finer 3”minus % finer # 4

20 Percent Particle Categories v To compute % Gravel subtract % finer than # 4 from % finer than 3” v To compute % Sand subtract % finer than # 200 from % finer than # 4 v Percent Fines is % finer than # 200

21 Activity 8 For 7 samples, fill out Activity

22 Additional Definitions v To Classify Clean Coarse-Grained Soils, you must first plot grain-size curve and determine three parameters D 10, D 30, D 60

23 Determining D 10, D 30, and D 60 D 10, millimeters 10 % finer D 30, millimeters 30 D 60, millimeters 60

24 Computing CU and CC Coefficient of Uniformity Coefficient of Curvature High Values Indicate Well- Graded Soil Values Between 1-3 Indicate Well-Graded Soil

25 Activity 9 Plot Curve from Data, compute CU Value

26 Activity 10 Plot Curve from Data, compute CC Value

27 C haracterizing Clean Sands and Gravels Particle Size % Finer Well graded Clean Well Graded Sands and Gravels have less than 5 % fines and a wide range of particle sizes that are equally distributed

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

29 Clean, Well/Poorly Graded Definitions v Sands –less than 5 % fines –CU > 6 –CC = 1-3 v Gravels –less than 5 % fines –CU > 4 –CC = 1-3

30 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

31 Activity 12 Review Example Soil

32 Activity 13 Use Flow Chart, Classify Soil

33 Activity 14 Summary of Classifications of Coarse-Grained Soils v 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

34 Dirty Coarse-Grained Soils v If a sample has less than 50 % Fines v And it has more than 12 % Fines, it is a Dirty Coarse-Grained Soil v To Classify, follow the flow chart and the following steps

35 Dirty Coarse-Grained Soil v Determine whether there is a greater % of Sand or Gravel –% G = % finer 3” minus # 4 –% S = % finer # 4 minus # 200 v Determine where minus # 40 fines plot on plasticity chart

36 Dirty Sands and Gravels v SC - Fines Plot Above A-Line v SM - Fines Plot Below A-Line v SC-SM - Fines Plot in Hatched Zone v GC - Fines Plot Above A-Line v GM - Fines Plot Below A-Line v GC-GM - Fines Plot in Hatched Zone Sands Gravels

37 Activity 16 - Problems

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

39 Activity 18 - Problem

40 Activity 20 - Review Questions

41 Activity 21 - Comprehensive Problems


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