Soil Compaction

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Success of Embankment

• Proper preparation of foundation.

• Use of suitable materials.

• Proper placing working and compacting of materials.

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Proper Preparation of Foundation

• Clear and grub area• Cut vegetation• Remove perishable material• Strip and stockpile• Compact area

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Suitable Materials

• Rock• Sand• Silt• Clay• See Standard specifications list

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Unsuitable Materials

• Organic soils should not be used as embankment or subgrade material.

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Proper Placement and Compaction

• Placing layers

• Placing in marsh

• Placing rock

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Placing Layers

• The maximum thickness of a layer should not exceed 8 inches loosely placed.

• 8 inch lifts

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Placing Layers

• Compact each layer

• Level each layer

• Parallel

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Placing in Marsh

• Typically in wet marsh excavations WisDOT allows for marsh backfill to be end dumped into excavation and “surged” down into the excavation with a bulldozer until above water level.

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Placing Rock

• No end dumping• Bulldozed or shoved into position• Various sizes• When placing rock all voids must be filled with

finer material.

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Principles of Compaction

1. Decrease future settlements

2. Increase shear strength

3. Decrease permeability

4. Increase stability

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Not Achieving Compaction?Solutions

• Increase compaction effort–Compaction equipment

• Change soil moisture content–Optimum moisture content

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Figure 1: Compaction Equipment

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Figure 1: Compaction Equipment

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Static smooth drum roller works well for sealing subgrades after the days grading operations are complete.

Doesn’t work well on clay soils.

Standard Compaction

• Embankment compaction

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Special Compaction

• Density tests–Sand Cone Method–Nuclear Method

• Minimum frequency

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Moisture Control

• Proper moisture conditions are essential for the efficient compaction of earth embankments. Satisfactory moisture conditions almost always are specified in relation to the optimum moisture content for a standard laboratory compaction test.

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Moisture Control

• Discs for wet cohesive soils

• Blade crown on surface

• Mixed

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Documentation- Cut sections

• Excavated proper grade• Frost susceptible materials• Compaction• EBS• Drainage• Proper disposal

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Documentation- Embankments

• Preparation of foundation

• Soils utilized

• Placing and compacting of materials

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Documentation-Entries

• Soil type• Moisture content• Layer thickness• Drying or wetting• Routing pattern

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Earthwork Equipment

• Hauling• Leveling• Aerating• Compacting

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Figure 2: Track Dozer

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Track Dozer

• Track Dozers are not to be used as compaction equipment.

• Used to level lifts of fill.

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Subgrade Care

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Figure 3:Disc Drying

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Disc Drying

• Drying of wet soils is necessary and can be accomplished by using graders, discs or harrows.

• Aeration of the soil• Necessary for compaction

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Figure 4: Rubber Tire Dozer

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Rubber Tire Dozer/Scrapers

• Hauling, Leveling and Compacting

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Figure 5: Sheepsfoot Imprint

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Sheepsfoot Imprint

• Optimum moisture–High volume compaction

• Lower water content–Increase soil surface

• Cohesive and semi-cohesive soils

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Figure 5: Motor-Grader

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Motor-Grader

• Aerates and levels

• Takes out ruts

• Not for compaction

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Figure 6: Solid Subgrade

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Solid Subgrade

• Keeps subgrade bladed up.• Keeps ruts out.

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Figure 7: Excessive Rutting

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Excessive Rutting

• Material too wet• Solutions:

–Motor-grader– Tractor–Disc

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Figure 8: Embankment construction

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Embankment Construction Equipment

• Dozer

• Tamping Roller

• Motor-Grader

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Figure 9: Dumping and Leveling

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Dumping and Leveling

• Firm and unyielding support.• Prior to first lift.

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Figure 10: Tamping Virbratory Roller

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Tamping Vibratory Roller

• “Dry”, bony material doesn’t stick.

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Figure 11: Excellent Material

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Excellent Material

• Dry and granular• Some rock• Imprints stand out• Not common in WI

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Figure 12: Good Conditions

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Good Conditions

• Back tire of grader is not sinking.

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Figure 13: Scraper End Dumping

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Scraper End Dumping

• Pushed into wet area.–Granular material

• Seal first lift• Don’t trap unstable soil in embankment.

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