1. Soil Classification

2. What is Soil?
Gravel
Clay
Silt
Sand

3. Testing the Soil
Bearing Capacity
Settling Characteristics
Drainage

4. Site Planning Function of Structure Site Profile (Contour Map)
Geological Information
Soils Sample Data

5. 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.

6. Unified Soil Classification System
Coarse-Grained Soils
Fine Grained Soils
Highly Organic Soils
Professional Development Lesson ID Code: 8006

7. Unified Soil Classification System

8. Sieve Sizes Gravels range from 3” down to the size of peas.
Silt and clay can pass through the #200 sieve.

9. Click here to open the Grain Size Chart.

10. Gravel Identification

11. Sand Identification

12. 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.

13. Clean vs. Dirty Graded Soil
Clean: contains little or no fines (<5%)
Dirty: contains an appreciable amount of fines ( >12%)

14. Clay or Silt? Dry Strength – crushing characteristics
Dilatancy – reaction to shaking
Toughness – consistency near plastic limit

15. Grain Shape

16. 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.

17. 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.

18. Soil Groups Soil Type Gradation Liquid Limit Gravel- G Sand-S Silt-M
Clay-C
Organic O
Peat- Pt
Well Graded- W
Poorly Graded - P
LL over 50- H
LL under 50 -L