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Soil Classification. What is Soil?. Gravel. Clay. Silt. Sand. Testing the Soil. Bearing Capacity Settling Characteristics Drainage. Site Planning. Function of Structure Site Profile (Contour Map) Geological Information Soils Sample Data. Soil Samples. Samples Represent the Site
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What is Soil? Gravel Clay Silt Sand
Testing the Soil Bearing Capacity Settling Characteristics Drainage
Site Planning Function of Structure Site Profile (Contour Map) Geological Information Soils Sample Data
Soil Samples • Samples Represent the Site • Taken about 1’-2’ below surface • Boring samples are taken at various locations and depths below the surface (subsurface) for deep foundations.
Unified Soil Classification System • Coarse-Grained Soils Fine Grained Soils Highly Organic Soils Professional Development Lesson ID Code: 8006
Gravels range from 3” down to the size of peas. Silt and clay can pass through the #200 sieve. Sieve Sizes
Grain Size Click here to open the Grain Size Chart.
Graded Soil • Well-Graded Soils-have a good representation of all particle sizes from the largest to smallest • Poorly-Graded Soils-two types • Uniformly-has soil particles nearly the same size. • Gap-Graded-contains both large and small particles but the graduation continuity is broken by the absence of some particle sizes.
Clean vs. Dirty Graded Soil • Clean: contains little or no fines (<5%) • Dirty: contains an appreciable amount of fines ( >12%)
Clay or Silt? • Dry Strength – crushing characteristics • Dilatancy – reaction to shaking • Toughness – consistency near plastic limit
Soil Color • * Can vary with moisture content • * May indicate the presence of certain chemical or impurities • * Dark brown /black may indicate organic material. • * Gray, olive green indicate inorganic soils. • * Gray-blue or gray-yellow indicates poor drainage. • * Red or yellow may indicate iron oxides. • * White to pink may indicate considerable silica, calcium carbonate, or aluminum compounds.
Plasticity Atterberg Limits: Plastic Limit-lowest moisture content at which soils can be rolled into 1/8” diameter thread without breaking. Liquid Limit- minimum moisture content at which soil will flow when a small shear or cutting force is applied.