Soils of Wisconsin

Topic C

Topic C

Soil

Uncemented aggregate of mineral grains and decayed organic matter with liquid and gas in the empty spaces between the solid particles.

Topic C

Topic C

Types of Soils

1. Granular Soils – Sand and Gravel

2. Fine Grained Soils – Clays and Silts

3. Organic Soils – Topsoil and Peat

Topic C

1.Granular Soils • Sand and Gravel• Excellent foundation, embankment and backfill

material.• Not susceptible to frost• High permeability• Settle rapidly while loaded• Develops strength through particle

contact/friction.

Topic C

Granular Soils – StructureStrength Development

Topic C

1.Granular Soils • Sand and Gravel• Excellent foundation, embankment and backfill

material.• Not susceptible to frost• High permeability• Settle rapidly while loaded• Develops strength through particle

contact/friction.

Topic C

Gravel

• Larger Particles• More pervious• More stable• Less affected by

water or frost

Sand

• Finer Particles–Feels gritty

• Finer and smoother it is closer to silt.–Decreased

permeability–Reduced stability

in waterTopic C

2. Fine Grained Soils

1. Silts – Nonplastic

2. Clays - Plastic

Topic C

Plastic

Capable of being shaped or formed.

Topic C

2. Fine Grained Soils • Soil passing a No. 200 sieve

• Silts = 0.075 mm to 0.002 mm (0.003 in to 0.00008 in)

• Clays – less than 0.002 mm (0.00008 in)

Topic C

2. Fine Grained SoilsCharacteristics

• Low shear strengths• Poor construction material• Practically impervious• Highly susceptible to frost• Develops strength from particle bonds• Higher amount of energy needed to compact

(particularly clay soils)Topic C

Clay Particles Structure

Topic C

Clay Particles Structure

Topic C

• Non-plastic• Unstable in water.• Change volume

when shape changes.

• Pulverized by finger when dry.

Silts Clays• Plastic• Compressible• Wet–Low resistance

to deformation.• Hard cohesive

mass when dry.• Impervious.

Topic C

3. Organic Soils• Topsoil

• Peat

• Rootmat

• Organic matter

Topic C

3. Organic Soils

• Not suitable for foundations or construction materials.

• Unacceptable roadway material.

Topic C

Organic Soils

1. Reduced load-carrying capacity

2. Low Shear Strength

3. Increased compressibility

4. Releases toxic gases upon decay

Topic C

Water and Soil• Necessary Evil• Critical to compaction effort• Reduces strength of soil• Loss of Stability• Groundwater moves soil particles• Erosion• Amount of water influences permeability and frost action.

Topic C

Effects of Water on Soil• Concentrated zones of groundwater on a

cut slope cause the soils to flow down the slope.–Often exists where a fine sand or silt

overlays an impervious soil (clay).

Topic C

• Seepage zones in backslopes causes slumping or sliding of slopes.

Topic C

Topic C

Topic C

Topic C

Topic C

Topic C

Topic C

Topic C