The soil classification methods were developed step by step with different ideas. USCS Example 0 10 20 30 40 50 60 70 80 90 100 0.001 0.01 0.1 1 10 Grain Size, mm % Passing P 4=93% %G=7 P 200 = 20% %S&G=80 %S=73 200 4 USCS Example nP 4 =93%, P 200 =20%, %G=7, %S=73 nLL = 35 PL = 20 PI = 15 nBecause P 200 <50%, Coarse Soil nBecause %S>%G, Sand nBecause P 200 >12%, use plasticity chart USCS Plasticity Chart LL = 35, PI = 15 Soil fines are Clay maximum size; rounded and subangular sand grains, coarse to fine; about 15% non plastic fines with low dry strength; well compacted and moist in place; alluvial sand (SM). Subsurface exploration and sampling Soil classification. 40 sieve – 50% passing the No. 2. Example: Silty sand gravelly; about 20% hard, angular gravel particles 1/2in. A geotechnical engineering soil classification example using the Unified Soil Classification System (USCS). 4 sieve -% passing the No. 40 35 No. Major divisions Test criteria Group symbols Passing 75 μ m sieve Other test criteria* COARSE GRAINED SOILS … % Coarse grained soil (gravel and sand) = 100 -% passing the No. Extended soil groupings for coarse‐grained soils defined by specific laboratory test values, as used in ASTM D2487. Soil classification system groups soils based on its performance given a particular condition. The Unified soil classification system. Important Notes :- American Association of State Highway and Transport Officials (AASHTO) soil classification system is based on the particle size and the plasticity characteristics. 200 F200 R200 F4 R4 4.75 mm 0.075 mm Dr. Abdulmannan Orabi IUST 13. The USCS places emphasis on particle size and uses the percentage retained on Sieve No. (Note: Show All The Criteria Used For Classifying Each Soil, Including The Group Symbol And The Group Name.) system. The classification system can be applied by unconsolidated material and represented by two-letter symbols. Grain size (gravel, sand, silt, clay, organic) 2. Plus you can quickly compare which end member classification most closely resembles the natural soil. Originally developed by Casagrande (1940), the Unified Soil Classification System (USCS) was used for air field construction during World War II. % Fine grained soil (silt and clay) = % passing the No. Then soil was classified depending on texture which was finally developed to triangular classification diagram method. Although earth materials may be soil, rock, or combi-nations of soil and rock, this chapter focuses focus on soil materials. Soil A: U.S. Sieve Size Percent Passing No. 200 sieve. CIVL 3101 Soil Mechanics Course Notes Dr. Craig Lake, P.Eng 1 CHAPTER 1: INTRODUCTION TO GEOTECHNICAL ENGINEERING AND SOIL CLASSIFICATION What you should learn in this chapter: How soil and water are investigated in the field How soils are classified by size How soils are classified by behavior (i.e. plasticity) How to classify soil using the Unified Soil Classification System (USCS) … % Sand = % passing the No. For example, GW-GM corresponds to "well-graded gravel with silt." Take a representative sample of soil (excluding particles >75 mm) (see Note 1) and classify the soil as coarse-grained or fine-grained by estimating whether 50% by weight, of the particles can be seen individually by the naked eye. Easily practice and calibrate your familiarity with baseline soil classifications. 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